Radiology Flashcards

(197 cards)

1
Q

A 56-year-old man presents to the emergency room
with 1 week of altered mental status. His medical
history is significant for a glioblastoma treated with
resection followed by temozolomide therapy and
whole brain radiation 1 year ago. An MRI is performed, and contrast-enhanced, diffusion-weighted,
and apparent diffusion coefficient sequences are
shown in these images. Perfusion maps (not shown)
demonstrate decreased relative cerebral blood volume. What is the likely cause of his new symptoms?
A. Radiation necrosis
B. Recurrent glioblastoma
C. Secondary tumor caused by chemotherapy
regimen
D. Encephalomalacia from tumor resection

A

A. Radiation necrosis

Radiation necrosis typically presents with higher apparent diffusion coefficient (ADC) values compared with tumor recurrence, which tends to show restricted diffusion and therefore lower signal in the solid enhancing components. On perfusion MRI,
radiation necrosis demonstrates decreased relative cerebral blood volume (rCBV) in contrast to highgrade tumors. Finally, this patient is 1 year from his radiation therapy, which is a peak time for radiation necrosis to appear (usually between 12 and 24 months). (B) A recurrent glioblastoma would tend to have a low ADC signal and increased perfusion on rCBV maps. (C) Secondary malignancies following temozolomide (an alkylating agent) have been reported but are a rare occurrence. These malignancies usually are hematologic. Glioblastoma would be much more likely than a secondary malignancy, given its aggressive nature and expected eventual recurrence. (D) Encephalomalacia would be apparent by parenchymal volume loss and should not
show nodular enhancement or restricted diffusion. Some (usually nonnodular) enhancement may be present around the resection cavity due to granulation tissue

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2
Q

The lesion shown in these images depicts a(n):
A. Optic nerve glioma
B. Meningioma
C. Chordoma
D. Esthesioneuroblastoma

A

D. Esthesioneuroblastoma

Esthesioneuroblastomas (olfactory neuroblastomas) are rare, malignant tumors of the superior nasal cavity and anterior skull base. Treatment strategies vary widely and include surgery, radiotherapy, and/or chemotherapy. The ideal treatment
modality has yet to be determined. Esthesioneuroblastomas tend to exert mass effect on the orbits, optic nerves, and optic chiasm, and may result in proptosis. They can occur in the frontal sinus and have variable intracranial extension. They homogeneously enhance on contrasted T1 sequences and
appear moderately hyperintense on T2 sequences. (A) An optic nerve glioma would infiltrate and expand the optic nerve. As seen in the second image, there is stretching of the optic nerve due to mass effect and proptosis, but the tumor itself does not involve the optic apparatus. (B) Anterior skull base meningiomas also demonstrate avid enhancement and occasionally can extend into the olfactory recess. They may present with a dural tail
and hyperostosis; however, the epicenter of the mass in this case is in the sinonasal cavity without a significant intracranial dural component. This makes a meningioma unlikely. Esthesioneuroblastomas often do extend intracranially, in which case a “waist” at the level of the cribriform plate and cysts at the brain–tumor interface are strongly suggestive of such diagnosis. (C) Skull base chordomas usually are located in the anterior clivus but
rarely may extend to the nasal cavity. Primary
chordomas in the nasal cavity and maxilla without clival involvement are extremely rare. Chordomas usually demonstrate more heterogeneous enhancement than esthesioneuroblastomas on contrasted
T1 sequences and are very hyperintense on T2
sequences.

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3
Q

What likely is associated with the imaging findings
on the MR susceptibility-weighted imaging (SWI)
sequence shown in these images?
A. Shearing injury from rotational acceleration
B. β-amyloid peptide deposits
C. Mutations in the CCM1 gene
D. Long bone fractures

A

D. Long bone fractures

Long bone fractures can result in fat embolism,
which appears as tiny foci of susceptibility artifact
that preferentially may be located at the gray matter–white matter interface or diffusely distributed
as in this case. Fat embolism may be accompanied
by scattered foci of restricted diffusion. (A) Diffuse
axonal injury is due to shearing forces from rotational acceleration. Areas of hemorrhage can be
detected on susceptibility-weighted imaging (SWI)
sequences and tend to be located in the gray
matter–white matter junction, corpus callosum,
and brainstem. Linear SWI signal loss often can be
seen along the white matter tracts. (B) β-amyloid
peptide deposits are related to cerebral amyloid
angiopathy (CAA). SWI may show multiple foci
of signal loss located peripherally in a cortical/
subcortical distribution rather than diffusely as
in this case. Patients also can have superficial siderosis and present with subarachnoid hemorrhage.
(C) Mutations in the CCM1, CCM2, and CCM3 genes
can be seen in familial cavernous malformation
syndromes. Lesions usually are more randomly
distributed and not as evenly sized as in the current case.

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4
Q

A 22-year-old man without a significant medical
history presents with progressive midthoracic pain.
An MRI examination of the spine is shown in these
images. What is the most likely diagnosis?
A. Astrocytoma
B. Ependymoma
C. Metastasis
D. Tumefactive demyelination

A

A. Astrocytoma

Astrocytomas in the spinal cord are most common in children but also may occur in adults. The
majority of them are histologically low grade and
slow growing, and may result in bone remodeling.
Half of astrocytomas are of the pilocytic subtype
and are relatively well defined, whereas the
remainder are infiltrative. They commonly present
as expansile masses with variable degrees of illdefined enhancement, although some tumors may
not enhance. (B) Ependymomas are more common in adults. Compared with astrocytomas, their
enhancement more frequently is well defined, and
they more commonly are associated with cystic
changes or hemorrhage. They are located more
centrally, as they arise from the ependyma, but
such distinction becomes difficult in larger tumors.
(C) Metastases to the cervical spine typically are
more focal than and not as expansile as the demonstrated lesion. It would be highly unusual for a
patient of this age to present with a spinal cord
metastasis without a known primary malignancy.
(D) Tumefactive demyelination is more common
in the brain. Demyelinating lesions may be seen in
the spinal cord and may be related to acute disseminated encephalomyelitis (more common in
the cervical spine), neuromyelitis optica (which
may result in longitudinally extensive transverse
myelitis), and multiple sclerosis (usually with small
lesions centered in the peripheral white matter
and only rarely extending over long segments when
confluent). The appearance of the lesion in question is too expansile and is not compatible with a
demyelinating or inflammatory process.

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5
Q

A neonate underwent an MRI of his brain, shown
in this image. What may be an associated finding?
A. Interhemispheric cysts
B. Collapse of ventricular atria and occipital horns
C. Low-riding third ventricle
D. Curvilinear pericallosal lipomas

A

A. Interhemispheric cysts

The image accompanying the question shows
dysgenesis of the corpus callosum with incomplete
formation of the cingulate gyrus. Dorsal or occasionally anterior interhemispheric cysts are a common finding. (B) Colpocephaly (dilatation of the
atria and occipital horns of the lateral ventricles) is
a characteristic secondary finding in dysgenesis of
the corpus callosum. (C) Patients with dysgenesis
of the corpus callosum can have a “high-riding”
third ventricle. Additional findings include bundles of Probst (white matter that failed to cross the
midline) and incomplete rotation of the hippocampi. (D) Tubulonodular lipomas have a significantly increased incidence of associated anomalies
compared with curvilinear ones.

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6
Q

What is a characteristic of the lesion depicted in
the MRI study shown in these images?
A. Results from premature disjunction of the
cutaneous ectoderm from the neuroectoderm
during neurulation
B. Infiltrative hypercellular lesion with variable
degrees of mitosis/atypia
C. Results from clonal transformation of cells of
B-cell origin
D. May be associated with endolymphatic sac
tumors, ren

A

A. Results from premature disjunction of the
cutaneous ectoderm from the neuroectoderm
during neurulation

Postcontrast sagittal T1 and short tau inversion
recovery (STIR) images show a large lobulated
mass that appears to be intradural and at least partially intramedullary. Although most of the mass
is hyperintense on T1, these areas fully suppress
on STIR images, indicating that this signal is related
to fat rather than contrast enhancement. Spinal
lipomas follow fat signal on all sequences, and subcutaneous fat can be used as an internal control.
Embryologically, these lesions result from premature disjunction of the cutaneous ectoderm from
the neuroectoderm during neurulation, whereby
the open neural tube becomes exposed to the
ingrowth of mesodermal tissues. Patients may
experience slowly progressing paresis, spasticity,
or sensory loss depending on the extent and location of the lesion. (B) An infiltrative hypercellular
lesion with variable degrees of mitosis/atypia would
describe a neoplastic process such as an astrocytoma, which may or may not show enhancement.
(C) Clonal transformation of cells of B-cell origin
would result in lymphoma (e.g., Hodgkin). These
lesions are rare in the spinal cord and usually
enhance. (D) Hemangioblastomas are very vascular and avidly enhance. They can occur in the spinal cord or leptomeninges. They may be associated
with endolymphatic sac tumors, renal cell carcinomas, retinal angiomas, pheochromocytomas, and
cystic lesions.

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7
Q

A 30-year-old woman with a history of recurrent
genital and oral aphthae and erythema nodosum
underwent an MRI of the brain. What is a likely
imaging finding in this patient?
A. Enhancing lesion involving the brainstem
B. Fluid-attentuated inversion recovery (FLAIR)
hyperintense lesion sparing red nuclei and
substantia nigra
C. Lesions with a leading edge of restricted
diffusion
D. Lesions involving the pulvinar and dorsomedial thalamic nuclei
E. Lesions with an incomplete rim of enhancement

A

A. Enhancing lesion involving the brainstem

Manifestations of Behçet disease in the central
nervous system are varied. The brainstem is the
most commonly affected, and lesions can be focal
or multifocal. There usually is associated edema
and contrast enhancement, particularly in the acute
phase. Patients also can present with meningoencephalitis and nonspecific white matter lesions.
(B) T2/FLAIR hyperintensity in the brainstem sparing the red nuclei and substantia nigra commonly
is described in Wilson disease. (C) A leading edge
of restricted diffusion can be seen in large or new
lesions in progressive multifocal leukoencephalopathy. (D) Lesions involving the pulvinar and
dorsomedial thalamic nuclei are characteristic
of variant Creutzfeldt-Jakob disease. (E) Active
demyelination can present with an incomplete
rim of enhancement.

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8
Q

A 54-year-old man underwent an MRI of the spine.
Sagittal and axial postcontrast T1-weighted images
are shown in these images. What is the patient’s
likely diagnosis?
A. Leptomeningeal metastasis
B. Neurofibroma
C. Schwannoma
D. Meningioma

A

D. Meningioma

The demonstrated homogeneously enhancing
dural-based mass along the left ventral aspect of
the spinal canal at the level of C2 is most consistent
with a meningioma. It is more common in females
and, when in the spine, it most frequently occurs
in the thoracic region. It nearly always is completely intradural, but also may protrude through
the neural foramina, resulting in a “dumbbell”
configuration and thus may look similar to schwannomas. (A) Leptomeningeal metastases usually
develop along the pial surface of the cord and spinal nerves. The lesion in question is dural based.
(B) Neurofibromas may be indistinguishable from
schwannomas by imaging. They may show a socalled target sign with central hypointensity on
T2-weighted sequences due to a fibrocollagenous
core. (C) Schwannomas tend to enhance more
avidly and heterogeneously than meningiomas,
particularly due to the presence of cystic changes
and hemorrhages in larger lesions. They follow the
course of the involved nerve and do not show a
dural base. Although not entirely specific, they can
extrude through and expand the neural foramina,
resulting in a “dumbbell” configuration.

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9
Q

The lesion shown in this image (arrow) can result
from injury to what structure?
A. Central tegmental tract
B. Lateral lemniscus
C. Spinothalamic tract
D. Reticulospinal tract

A

A. Central tegmental tract

The axial FLAIR image accompanying the question demonstrates hyperintensity of the left inferior olivary nucleus in a patient with hypertrophic
olivary degeneration. This can be caused by a
lesion involving the triangle of Guillain-Mollaret,
a circuit connecting the dentate, red, and inferior
olivary nuclei. Efferent fibers from the dentate
nucleus ascend via the superior cerebellar peduncle
and decussate to the contralateral red nucleus, from
which fibers project inferiorly to the ipsilateral
inferior olivary nucleus through the central tegmental tract. Patients characteristically present
with palatal tremors. (B) The lateral lemniscus is
not part of the Guillain-Mollaret triangle. Bilateral
lesions are associated with hearing loss. (C) The
spinothalamic tract is a sensory pathway that
transmits pain and temperature sensation from the
spinal cord to the thalami. (D) The reticulospinal
tract transmits information from the reticular formation in the pons and medulla to the spinal cord.
It is not part of the Guillain-Mollaret triangle.

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10
Q

Axial T2 and postcontrast T1-weighted imaging of
the lumbar spine are shown in these images. To
what does the abnormality indicated by the arrow
correspond?
A. Disk protrusion
B. Epidural scar
C. Disk extrusion
D. Epidural abscess
E. Sequestered disk

A

B. Epidural scar

The axial T2 images accompanying the question show hypointense tissue projecting into the
right paracentral zone. This tissue shows diffuse
enhancement on the postcontrast image, and therefore is most consistent with scar. Note the evidence
of a prior right-sided laminotomy. (A, C, E) A disk
protrusion or extrusion or a sequestered disk
should not enhance. (D) There is no fluid collection
with peripheral enhancement to suggest an epidural abscess.

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11
Q

A 12-year-old girl is brought to the emergency
department in an obtunded state following an
episode of seizures. Based on these images, what
is the diagnosis?
A. Cortical venous thrombosis
B. Deep venous thrombosis
C. Mitochondrial encephalopathy
D. Hypoxic ischemic encephalopathy
E. Arterial infarction

A

B. Deep venous thrombosis

The sagittal noncontrast T1-weighted image
(right) accompanying the question shows increased
signal in the straight sinus, vein of Galen, and
internal cerebral veins due to thrombosis. Also note
the profound hypointensity of the thalami compared with the brain. The axial FLAIR image (left)
shows marked swelling of the basal ganglia and
thalami bilaterally due to venous infarction. Risk
factors for deep venous thrombosis include severe
dehydration and other hypercoagulable states such
as pregnancy, malignancy, and sepsis. Venous
infarction occurs in a nonarterial distribution and
may be complicated by hemorrhage. (A) Cortical
venous thrombosis may lead to lobar infarctions
sparing the deep gray structures. (C) Leigh disease
is a mitochondrial encephalopathy that may affect
the basal ganglia, periaqueductal gray, and cerebral peduncles. Changes in the putamina seem
to be a consistent feature. (D) Hypoxic ischemic
encephalopathy can occur following hypoxia, such
as in cardiorespiratory arrest, drowning, or various
forms of asphyxiation. In older children and adults,
the watershed zones initially may be affected after
mild insults, with more severe cases involving gray
matter structures, particularly the cerebral cortex,
basal ganglia, and hippocampi. Perinatal hypoxic
ischemic injury preferentially may affect the thalami, brainstem, and perirolandic cortex. There may
be white matter involvement in the setting of
global ischemia. (E) The imaging abnormalities in
this case do not follow an arterial distribution.

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12
Q

A woman underwent a head CT, shown in these
images. What is the likely diagnosis?
A. Infiltrative tumor
B. Acute infarct
C. Intracranial hemorrhage
D. Meningitis

A

C. Intracranial hemorrhage

There is a hemispheric subdural hematoma along
the right convexity that is isodense to the cortex.
This appearance can occur depending on when the
patient is imaged, as the density of blood decreases
over time and, at some point, will have the same
attenuation as cortex. The best way to recognize
such hematomas is to identify their associated mass
effect and the displacement of the darker white
matter, which can be seen medial to the hematoma. (A) An infiltrative tumor would involve the
cortex and white matter more diffusely. The demonstrated process is centered in the extra-axial space
and is subdural due to its overall crescentic shape
and the fact that it crosses sutures. (B) A noncontrast head CT in acute infarct may be normal, particularly in the first 6 hours after ictus. Early
findings include a hyperdense middle cerebral
artery territory, loss of gray matter–white matter
distinction in the basal ganglia or peripheral brain,
and loss of the insular ribbon. (D) The majority
of noncontrast head CT studies in meningitis are
normal, and patients sometimes may present with
hydrocephalus as an isolated finding. Areas of
edema due to cerebritis or intra- and extra-axial
abscesses may be seen in complicated meningitis.
Contrast studies, in particular MRI, may be able to
show the presence of leptomeningeal disease.

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13
Q

A boy with truncal ataxia and abnormal eye movements undergoes an MRI of the brain, which shows
continuation of the cerebellar hemispheres and
dentate nuclei and absence of the vermis. What is
the most likely diagnosis?
A. Pontine tegmental cap dysplasia
B. Rhombencephalosynapsis
C. Joubert syndrome
D. Dandy-Walker malformation

A

B. Rhombencephalosynapsis

Rhombencephalosynapsis is characterized by
an absent vermis and midline continuation of
the dentate nuclei, cerebellar hemispheres, and
superior cerebellar peduncles. It can be seen in
isolation or associated with other malformations
such as the VACTERL spectrum and Gomez-LopezHernandez syndrome. (A) Pontine tegmental cap
dysplasia is a rare hindbrain malformation that includes dysplasia of the cerebellar vermis, lateralized superior cerebellar peduncles, ectopic dorsal
transverse pontine fibers (tegmental cap), flattened ventral pons, absence of the inferior olives,
and absence or near absence of the middle cerebellar peduncles. (C) Joubert syndrome is characterized by vermian hypoplasia or aplasia and lack of
decussation of the superior cerebellar peduncles,
resulting in a “molar tooth” appearance. (D) A
Dandy-Walker malformation can result in cystic
enlargement of the posterior fossa in communication with the fourth ventricle. The vermis is
hypoplastic, but there is no continuation of the
cerebellar structures.

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14
Q

A 38-year-old man who sustained a gunshot wound
to the head underwent an emergent CT scan,
shown in this image. What finding portends the
worst prognosis?
A. Presence of both entry and exit wounds
B. Involvement of the inner and outer tables of
the calvaria
C. Bullet tract crossing the deep midline structures
D. Presence of metallic fragments along the bullet trajectory
E. Presence of an open comminuted fracture

A

C. Bullet tract crossing the deep midline structures

Various studies consistently have shown that
bullet tracts crossing the midline (i.e., bihemispheric involvement) are associated with increased
mortality and worse functional outcomes in those
patients who survive, although there are recent
data suggesting that individuals with isolated
bifrontal involvement may have a relatively better
prognosis. Other significant negative prognostic
factors include brainstem involvement, posterior
fossa injuries, transventricular injuries, low Glasgow
Coma Scale score, nonreactive pupils, and older age.
(A) The presence of both entry and exit wounds
is not a significant predictor of worse outcomes.
(B) Involvement of the inner and outer tables of
the calvaria is not a significant predictor of worse
outcomes. (D) The presence of bullet fragments
is not a significant predictor of worse outcomes.
(E) The presence of an open comminuted fracture
is not a significant predictor of worse outcomes.

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15
Q

The axial CT scan in this image shows the level of
termination of bilateral cerebral deep brain stimulation leads. What is the anatomic location of these
leads?
A. Globus pallidus interna
B. Subthalamic nuclei
C. Ventral intermediate nuclei
D. Red nuclei

A

A. Globus pallidus interna

The image accompanying the question shows
bilateral deep brain stimulator leads terminating
in the globus pallidus interna (GPi) that are used
to treat motor fluctuations in advanced medication
resistant Parkinson disease or levodopa induced
dyskinesia. (B) The subthalamic nuclei are an alternative target for deep brain stimulation in Parkinson disease. They are located at a lower level
superior to the substantia nigra, lateral to the red
nuclei, and medial to the internal capsule. (C) The
ventral intermediate nuclei are located in the ventral thalami just lateral to the red nuclei. They are a
common target for the treatment of essential tremors. (D) The red nuclei are paired, round T2 hypointense structures located in the rostral midbrain.

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16
Q

A man is reported to have a “string of pearls”
appearance on his angiogram. What is the likely
diagnosis?
A. Severe carotid artery stenosis
B. Dural arteriovenous fistula
C. Fibromuscular dysplasia
D. Arteriovenous malformation
E. Carotid artery dissection

A

C. Fibromuscular dysplasia

The medial type of fibromuscular dysplasia is by
far the most common and can show a “string of
pearls” appearance on angiography. The same descriptor also is sometimes used for cerebral vasculitis, which can show areas of alternating segmental
vascular stenoses and dilatation. (A) A “string sign”
sometimes is described with severe carotid artery
stenosis due to a very thin column of contrast flowing through the narrowed segment. (B) The “buzz”
term for a dural arteriovenous fistula is “retrograde cortical venous drainage” or “cortical venous
reflux,” which is associated with more aggressive
behavior and an indication for emergent treatment. (D) Arteriovenous malformations display early
draining veins and the presence of a nidus sometimes with venous or arterial aneurysms. (E) Carotid artery dissections can show a “string sign” in the narrowed segment; however, dissection of the internal carotid artery typically is associated with a “flame shape” configuration when it occurs just above the level of the carotid bulb.

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17
Q

A sagittal T2-weighted image of a patient with a
tethered cord is shown in this image. What is a
characteristic of the pathology represented here?
A. Reduced risk following folic acid supplementation
B. Associated with Chiari 2 malformations
C. Secondary to premature disjunction of the
neural ectoderm
D. Most cases are familial

A

C. Secondary to premature disjunction of the
neural ectoderm

Lipomyelomeningoceles, lipomyeloceles, and
lipomas are secondary to premature disjunction of
the neural ectoderm from the cutaneous ectoderm.
(A) Studies have not found a decreased incidence of
lipomyelomeningoceles following folic acid supplementation, suggesting that the pathogenesis
is different from that of other neural tube defects.
(B) Open myelomeningoceles are the sine qua non
of Chiari 2 malformations. Closed defects covered
by skin such as this one do not result in Chiari 2
malformations. (D) The vast majority of lipomyelomeningoceles are sporadic. A few familial cases
have been reported, but they are exceedingly rare.

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18
Q

What is the origin of the lesion on the contrastenhanced T1 image shown here?
A. Facial nerve
B. Vestibular nerve
C. Aberrant carotid artery
D. Inferior petrosal sinus

A

A. Facial nerve

There is an avidly enhancing mass involving the
right geniculate ganglion as well as the labyrinthine and canalicular segments of the right facial
nerve compatible with a schwannoma. The vast
majority of intracranial schwannomas arise from
the vestibular nerve followed by the trigeminal and
facial nerves. (B) A vestibular schwannoma would
not involve the facial nerve canal or geniculate
ganglion. (C) An aberrant internal carotid artery is
seen more inferiorly as a more lateral extension
of the internal carotid artery beyond the cochlear
promontory. It may appear as a pulsating “mass”
on clinical exam. (D) The inferior petrosal sinus
is located along the inferior aspect of the petrous
bone. It drains blood from the cavernous sinus into the jugular vein

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19
Q

A falcotentorial arteriovenous malformation is
noted to have its primary vascular supply from an
enlarged tentorial artery. What is the usual origin
of this vessel?
A. Meningohypophyseal trunk
B. Inferolateral trunk
C. Neuromeningeal trunk
D. Posterior cerebral artery

A

A. Meningohypophyseal trunk

The tentorial artery (of Bernasconi and Cassinari) is the most constant branch of the meningohypophyseal trunk, which in turn arises from the
cavernous internal carotid artery. It is an important structure due to its vascular supply to lesions
in the region of the tentorium cerebelli, such as
vascular malformations and meningiomas. (B) The
inferolateral trunk arises along the lateral aspect of the cavernous internal carotid artery and projects
inferiorly. It usually has three or four branches and
multiple anastomoses with branches of the external carotid artery. (C) The neuromeningeal trunk
is a branch of the ascending pharyngeal artery
and consists of jugular and hypoglossal divisions.
(D) The posterior cerebral arteries most commonly arise as bifurcations of the basilar artery

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20
Q

Sagittal CT and MRI STIR sequences of the cervical
spine are shown in these images. What is the
injury type demonstrated?
A. Hangman fracture
B. Clay-shoveler fracture
C. Jefferson fracture
D. Flexion-distraction injury
E. Locked facets

A

D. Flexion-distraction injury

The fracture demonstrated is a classic case of a
severe flexion-distraction injury with a teardroptype fracture of the anteroinferior C4 vertebra as
well as distraction of the C4-C5 facets and posterior elements as can be seen on the CT images. The
STIR image shows extensive edema in the posterior
soft tissues including the interspinous ligaments,
which are disrupted. These are highly unstable
fractures associated with acute anterior cervical
cord syndrome. (A) A hangman (or more correctly
“hangee”) fracture involves both pedicles or both
partes interarticulares of C2 and is secondary to
hyperextension and distraction. (B) A clay-shoveler
fracture is a stable fracture involving a lower cervical vertebra (usually C7) and sometimes the
upper thoracic spine. The fracture is a type of hyperflexion avulsion injury. (C) A Jefferson fracture
is a burst fracture of the C1 vertebra. It is considered unstable if the combined offset of the lateral
C1 masses measures more than 7 mm or if the
atlantodental distance measures more than 3 mm.
(E) Locked facets may be a result of a flexiondistraction injury and can result in listhesis. The
C4-C5 facets in this case are mildly distracted.

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21
Q

What MRI features would favor a metastatic (pathological) compression fracture over a benign osteoporotic fracture?
A. Horizontal low signal intensity bands
B. Convex posterior vertebral margins
C. Areas of spared vertebral marrow
D. Retropulsion of a bone fragment
E. Enhancement of the involved vertebra

A

B. Convex posterior vertebral margins

Convex posterior vertebral margins are suggestive of metastatic disease. Other features that would
support this etiology are epidural or paravertebral
masses or the presence of vertebral metastases at
other levels. Metastases tend to involve the pedicle
and posterior elements more commonly, but these
sites also can show edema related to benign fractures. (A) Horizontal low signal intensity bands can be seen on both T1- and T2-weighted images and are more common in benign osteoporotic fractures.
(C) Areas of spared vertebral marrow (best seen as
high signal on noncontrast T1 images) are seen
more commonly in benign compression fractures.
(D) Retropulsion of a bone fragment is more suggestive of a benign compression fracture. (E) Both benign and pathological compression fractures can be accompanied by significant enhancement.

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22
Q

A man with a history of depression presents with
rapid and involuntary movements involving his
face and limbs. The clinical exam is notable for
hypotonia, hyperreflexia, and mild bradykinesia. A
noncontrast CT of the head is shown in this image.
What mutation is the likely cause of the patient’s
presentation?
A. Trinucleotide repeat expansion
B. Point mutation
C. Frameshift mutation
D. Deletion

A

A. Trinucleotide repeat expansion

The CT shows atrophy of the heads of the caudate nuclei bilaterally, resulting in abnormal ballooning of the frontal horns of the lateral ventricles,
which is consistent with Huntington disease, given
the patient’s clinical presentation. Huntington
disease results from trinucleotide (CAG) repeat expansion in the huntingtin gene, which is located on
chromosome 4. (B) Point mutations are modifications of a single nucleotide base and include substitutions, deletions, and insertions. (C) Frameshift
mutations result from insertions, deletions, or
duplications that alter the normal trinucleotide
reading frame. (D) Deletions indicate of loss of
genetic material and can involve individual bases or an entire gene

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23
Q

Gradient echo MRI sequences are particularly useful for the detection or evaluation of what process
or pathology?
A. Myelin injury
B. Purulence
C. Acute ischemia
D. Glucose metabolism
E. Blood products

A

E. Blood products

Gradient echo (GRE) sequences generate images
that particularly are susceptible to magnetic field
inhomogeneities such as those produced in the
presence of paramagnetic blood degradation products (e.g., hemosiderin and ferritin). The presence
of these products manifests as signal loss and can
be used to detect hemorrhage. Dynamic susceptibility contrast MRI and functional MRI are different techniques based on GRE sequences. (A) Myelin
injury is difficult to demonstrate on conventional
MRI unless there is clear disruption of the white
matter. Certain metrics based on advanced MRI
techniques such as radial diffusivity (RD) in diffusion tensor imaging (DTI) may serve as indicators
of primary myelin injury. A different technique
called magnetization transfer can provide a measure of the contribution of protons that are bound
to macromolecules (e.g., myelin) and has been employed in the evaluation of demyelinating disorders. (B) Diffusion-weighted imaging (DWI) with
apparent diffusion coefficient (ADC) maps is very
sensitive for the detection of purulence within
abscesses, cavities, or the ventricular system.
(C) Acute ischemia is best demonstrated with DWI
and ADC maps. (D) Glucose metabolism can be
assessed with positron emission tomography (PET)
by using fluorodeoxyglucose (FDG).

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24
Q

A man without a history of trauma is brought to
the emergency department with nausea, vomiting,
and ataxia. Axial T2-weighted images of the neck
and posterior fossa are shown here. What is a characteristic of the lesion in the neck?
A. It may be related to connective tissue disorders.
B. The majority occur in patients older than 60
years of age.
C. Intradural lesions are more common.
D. Rupture is more common in extradural than
intradural lesions

A

A. It may be related to connective tissue disorders.

The image on the left shows somewhat crescentic and nearly circumferential mural thickening of
the left vertebral artery in a patient with a spontaneous dissection (compare with the normal dark
vascular flow void on the right). The image on the
right shows cerebellar infarcts. Minor or sometimes unrecalled trauma may account for some
cases of “spontaneous” dissection, and there is an
increased incidence in patients with connective
tissue disorders. (B) Vertebral artery dissection
occurs in young and middle age adults with a mean
age of presentation of 40 years of age. (C) Extradural vertebral artery dissections are more common than intradural ones. (D) Rupture is more
common in intradural vertebral dissections because
of a lack of external elastic lamina, fewer elastic
fibers in the media, and a thinner adventitial layer.

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25
A 56-year-old patient involved in a motor vehicle collision underwent a cervical spine CT scan, shown in these images. What is true of the osseous abnormality demonstrated? A. It is consistent with an acute type 2 odontoid fracture. B. It results from failure of fusion of the ossiculum terminale. C. It is associated with Morquio syndrome and multiple epiphyseal dysplasia. D. Orthotopic lesions are more likely to be unstable than dystopic lesions.
C. It is associated with Morquio syndrome and multiple epiphyseal dysplasia. ## Footnote An os odontoideum is a rare anomaly of the cervical spine characterized by a deformity of the odontoid process that appears as a smooth and well-corticated ossicle separated from the body of C2. There may be hypertrophy of the anterior C1 arch, as seen in this case. It may be orthotopic where the ossicle is in a relatively anatomic location with a gap between it and the body of C2, or dystopic where the ossicle is located in any other position. An increased frequency of os odontoideum has been reported in patients with multiple epiphyseal dysplasia and in Morquio, Down, and Klippel-Feil syndromes. (A) The ossicle above the body of C2 is round and features smooth, wellcorticated margins; therefore, the abnormality shown is not an acute fracture. (B) Failure of fusion of the ossiculum terminale usually results in a much smaller ossicle above an overall normal-appearing odontoid process (except for a small notch at the tip). The ossiculum terminale normally fuses with the body of the dens around age 12. When persistent, it usually is asymptomatic and rarely associated with instability. (D) An os odontoideum usually is asymptomatic and, in many instances, is discovered incidentally; however, it may be associated with instability due to hypermobility of C1 over C2. This immobility may lead to spinal cord or, less frequently, vertebral artery compression. Dystopic lesions are more likely to be unstable than orthotopic lesions.
26
A 52-year-old obese woman with a history of headaches presents to clinic. An MRI of the brain was obtained, and is shown in these images. What additional radiographic finding may be seen? A. Dural venous sinus stenosis B. Venous sinus engorgement C. Brainstem sagging D. Decreased mammillopontine distance
A. Dural venous sinus stenosis ## Footnote The axial T2 image shows distention of the optic nerve sheaths and prominence of the optic cups bilaterally due to an increased intracranial pressure and papilledema in a patient with idiopathic intracranial hypertension (pseudotumor cerebri). The sagittal CISS image on the right shows an expanded and partially empty sella turcica. Additional findings in these patients include dural venous sinus stenosis, enlargement of the Meckel caves, and cerebrospinal fluid arachnoid pits in the sphenoid bones. (B) Venous sinus engorgement is seen in intracranial hypotension, not hypertension, due to decreased cerebrospinal fluid volumes (and in keeping with the Monro-Kellie doctrine). (C) Brainstem sagging is a feature of intracranial hypotension. (D) Decreased mammillopontine distance is a sign of brainstem sagging in intracranial hypotension.
27
A woman who was involved in a motor vehicle collision underwent a CT of the cervical spine, which shows a fracture involving an occipital condyle. What structure is likely to be affected? A. Cranial nerve IX B. Cranial nerve X C. Cranial nerve XI D. Cranial nerve XII
D. Cranial nerve XII ## Footnote The hypoglossal canals course along the medial and superior aspects of each occipital condyle between the basiocciput and the jugular process. They transmit cranial nerve XII, which is at high risk of injury in the presence of condylar fractures. (A) Cranial nerve IX courses through the pars nervosa of the jugular foramen along with the inferior petrosal sinus. (B, C) Cranial nerves X and XI course through the pars vascularis of the jugular foramen along with the jugular bulb.
28
The lesion shown in this image is associated with a chromosome 13q deletion. What is a characteristic of this lesion? A. Has a tendency for leptomeningeal spread B. Anterior eye segment enhancement indicates disease infiltration C. Likely has high apparent diffusion coefficient values D. Likely has high signal intensity on susceptibility-weighted imaging
A. Has a tendency for leptomeningeal spread ## Footnote The axial T2 image shows a T2 hypointense mass involving the left posterior globe and left optic nerve extending posteriorly to the level of the chiasm. There are foci with even lower signal intensities within the globe consistent with hemorrhage. Although an optic glioma may cause enlargement of the optic nerve, involvement of the eye and deletion of chromosome 13q (which contains the RB1 gene locus) indicates a diagnosis of retinoblastoma. This is a highly malignant tumor that has a tendency for leptomeningeal spread. (B) Anterior eye segment enhancement generally represents reactive angiogenesis. (C) Retinoblastomas, as with other primitive neuroectodermal tumors, commonly have profoundly low apparent diffusion coefficient values due to high cellularity and restricted diffusion. (D) The lesion shown likely has areas of low signal intensity on susceptibility-weighted imaging due to calcifications and hemorrhage.
29
What is true regarding the lesion shown in this CT image? A. Usually heals well with traction and immobilization B. Usually considered stable C. Constitutes the most common type of fracture at this site D. Fracture occurs above the transverse band of the cruciform ligament E. Most likely fracture type to progress to nonunion
A. Usually heals well with traction and immobilization ## Footnote This is a type 3 fracture of the odontoid process extending from its base into the body of C2. These fractures are unstable, as they allow the odontoid process to move with the occiput as a unit; however, they have the best prognosis of all odontoid fracture types. They usually heal well with traction followed by bracing. (B) Although type 3 odontoid fractures have the best prognosis of all odontoid fracture types, they are considered unstable. (C) Type 2 odontoid process fractures are the most common. They occur across the base of the odontoid process at its junction with the body of C2. (D) Type 3 odontoid fractures occur inferior to the level of the transverse band of the cruciform ligament. (E) Type 2 odontoid process fractures are the most likely to progress to nonunion.
30
A patient with left-sided cranial neuropathies underwent a brain MRI study, shown in these images. What is a likely complication of this lesion? A. Malignant transformation B. Carotid-cavernous fistula C. Subarachnoid hemorrhage D. Posterior circulation infarcts
B. Carotid-cavernous fistula ## Footnote The axial precontrast T1 image on the left shows a round, mixed signal intensity lesion in the left cavernous sinus. Note a subtle horizontal band at the level of the lesion propagating in the phaseencoding direction compatible with pulsation artifact. The T2 image on the right shows areas of profound hypointensity. Findings are indicative of an aneurysm, which probably is partially thrombosed. Compared with anterior and posterior circulation aneurysms, cavernous carotid aneurysms have the lowest rate of rupture (posterior circulation aneurysms have the highest). Rupture of cavernous carotid aneurysms may result in direct carotid-cavernous fistulae. (A) Malignant transformation may be seen in certain neoplasms. The lesion in this case is an aneurysm. (C) Subarachnoid hemorrhage can occur from rupture of an intradural aneurysm. (D) Posterior circulation infarcts can be the result of embolic phenomena from aneurysms located more proximally in the posterior circulation.
31
What is a characteristic of the entity depicted on the digital subtraction angiographic images shown here? A. Cortical venous reflux denotes increased bleeding risk. B. Multiple lesions may be seen in KlippelTrenaunay-Weber syndrome. C. Deep venous drainage connotes increased surgical risk. D. Most have a primarily dural vascular supply
C. Deep venous drainage connotes increased surgical risk. ## Footnote With arteriovenous malformations, deep venous drainage, involvement of eloquent cortex, and larger nidal sizes connote an increased surgical risk and are part of the Spetzler-Martin grading system. (A) Cortical venous reflux is associated with an increased bleeding risk in patients with dural arteriovenous fistulas. The patient in this case has a pial arteriovenous malformation with a large nidus supplied from branches of the anterior and middle cerebral arteries. (B) Most arteriovenous malformations (98%) are solitary, but they rarely may be multiple particularly in patients with certain syndromes such as Osler-Weber-Rendu (who also can have microaneurysms), Wyburn-Mason, and craniofacial arteriovenous metameric syndromes (CAMS). Klippel-Trenaunay-Weber syndrome is characterized by capillary, venous, and lymphatic malformations as well as soft tissue and osseous hypertrophy. (D) Most arteriovenous malformations (75%) have a primary pial blood supply from the internal carotid artery; 15% have dual supply from the external carotid artery; 10% receive blood from both the internal and external carotid arteries.
32
What is a characteristic of the injury shown on this CT scan? A. Combined offset of the lateral C1 masses relative to C2 greater than 6 mm, which suggests disruption of the alar ligaments B. Frequently associated with diving head first into shallow water C. High frequency of neurologic injury D. Most commonly occurs in infants and young children E. Usually warrants emergent surgical fixation
B. Frequently associated with diving head first into shallow water ## Footnote This is a burst fracture of C1 (also known as Jefferson fracture) that develops due to axial loading transmitted through the occipital condyles into the C1 vertebra and is seen frequently after diving head first into shallow water. Jefferson fractures tend to be stable, and neurologic deficits are infrequent unless there is disruption of the transverse ligament, fractures at other levels, or injury to the vertebral arteries. Disruption of the transverse ligament is suspected if there is widening of the atlantodens interval (normally less than 3 mm in adults and 5 mm in children) or if the combined offset of the lateral masses of C1 relative to the lateral C2 pillars measures greater than 6 mm. If the transverse ligament is disrupted, stability depends on the alar ligaments connecting the dens with the medial aspect of the occipital condyles. (A) Combined offset of the lateral C1 masses relative to C2 greater than 6 mm suggests disruption of the transverse ligament and raises concern about an unstable fracture. (C) Jefferson fractures have a low frequency of neurologic injury unless there is disruption of the transverse ligament, fractures at other levels, or injury to the vertebral arteries. (D) Jefferson fractures are extremely rare in infants and young children, probably due to the plasticity of their bones and the presence of soft synchondroses. (E) These fractures usually are managed conservatively unless they are unstable.
33
The abnormality in the left frontal lobe on the CT of the head shown in this image is consistent with what process? A. Acute infarction B. Cortical contusion C. Remote injury D. Neoplasm E. Abscess
C. Remote injury ## Footnote The area of hypoattenuation in the left frontal lobe is consistent with encephalomalacia. It demonstrates very low attenuation and is associated with volume loss, as can be seen by ex vacuo expansion of the frontal horn of the left lateral ventricle. This likely is secondary to remote trauma, infarction, or other injury. This patient also has an acute, right frontal, extra-axial hematoma. (A, B) Acute or subacute infarction or cortical contusion would not be associated with volume loss, and the lesion margins would likely be less well defined. (D) A neoplasm would show some degree of mass effect and may have surrounding edema. (E) There is no fluid collection or evidence of vasogenic edema to suggest an abscess.
34
What entity is compatible with the abnormality indicated by the arrow on the MRI shown in this image? A. Ependymoma B. Neuromyelitis optica C. Subacute combined degeneration D. Infectious myelitis
C. Subacute combined degeneration ## Footnote Subacute combined degeneration is caused by vitamin B12 deficiency, and leads to demyelination and vacuolization of the dorsal columns of the spinal cord with or without involvement of the lateral columns. It most commonly occurs in the upper thoracic and cervical cord. MRI shows T2 signal hyperintensity with rare contrast enhancement. Subacute combined degeneration can be exacerbated or caused by nitrous oxide toxicity, which temporarily interrupts metabolism of B12. (A) There is no evidence of a space-occupying lesion to suggest a neoplasm. Ependymomas tend to occur centrally within the spinal cord, and cysts, hemorrhage, and calcifications are common findings. (B) Neuromyelitis optica results in greater cord expansion than demonstrated in the image and usually is more central and not confined to the dorsal columns. (D) Infectious myelitis is rare, and imaging may show edema that is not confined to the dorsal columns.
35
A patient with extensive T2 hyperintensity and enhancement of the skull base shows a “black turbinate” sign on postcontrast T1 MRI sequences. What is the likely etiology of these findings? A. Bacterial infection B. Invasive fungal infection C. Nasopharyngeal carcinoma D. Osseous infarction
B. Invasive fungal infection ## Footnote The “black turbinate” sign refers to nonenhancing nasal mucosa due to tissue infarction, and has been described in angioinvasive fungal infections. The skull base findings in this case are secondary to fungal osteomyelitis. (A) Bacterial infection can lead to osteomyelitis of the skull base but does not result in a “black turbinate” sign. (C) Nasopharyngeal carcinoma can invade the skull base but does not produce a “black turbinate” sign. (D) Osseous infarctions can present with mixed signal intensities on T2-weighted MRI sequences due to areas of edema and sclerosis and irregular enhancement. Skull base infarcts are rare but occur more commonly in patients with sickle cell disease, in which case they can be complicated by osteomyelitis.
36
What explains the development of the abnormality demonstrated on the brain MRI shown in these images? A. Failure of closure of the rostral neuropore B. Failure of diverticulation C. Nondisjunction of the neural ectoderm D. Premature disjunction of the neural ectoderm
B. Failure of diverticulation ## Footnote These images show nonseparation of the frontal lobes and an azygous anterior cerebral artery in a patient with lobar holoprosencephaly. These occur secondary to the failure of diverticulation and cleavage of the prosencephalon during embryonic life. Holoprosencephaly represents a spectrum of abnormalities, with the alobar form being the most severe and commonly presenting with a monoventricle, thalamic fusion, and facial anomalies. (A) Failure of closure of the rostral neuropore leads to anencephaly. (C) Nondisjunction of the neural tube can result in open spinal dysraphisms. (D) Premature disjunction of the neural tube can lead to lipomyeloceles, lipomeningoceles, and lipomyelomeningocele
37
What tumor type would be expected to show the lowest apparent diffusion coefficient (ADC) values on an MRI of the brain? A. Atypical teratoid rhabdoid tumor B. Juvenile pilocytic astrocytoma C. Ependymoma D. Dysembryoplastic neuroepithelial tumor E. Diffuse astrocytoma
A. Atypical teratoid rhabdoid tumor ## Footnote Atypical teratoid rhabdoid tumors and other embryonal tumors as well as medulloblastomas are highly malignant and typically show the lowest apparent diffusion coefficient (ADC) values due to their high cellularity. (B) Juvenile pilocytic astrocytomas are WHO grade I tumors that do not show significant restricted diffusion. (C) Ependymomas may show variable degrees of restricted diffusion, but their ADC values typically are higher than those of embryonal tumors. (D) Dysembryoplastic neuroepithelial tumors are benign glioneuronal neoplasms (WHO grade I) that do not show restricted diffusion; therefore, their ADC values are high. (E) Diffuse astrocytomas are WHO grade II lesions that do not show significant restricted diffusion.
38
What is a characteristic of acute demyelinating encephalomyelitis? A. Most cases occur following vaccination. B. Deep gray nuclei usually are spared. C. Most lesions show contrast enhancement. D. It is typically a monophasic process.
D. It is typically a monophasic process. ## Footnote Acute demyelinating encephalomyelitis (ADEM) usually is a monophasic process, but some patients are at an increased risk of recurrence (defined as a new event after 3 months) or the development of multiple sclerosis. (A) Approximately 75% of cases of ADEM occur after viral and less commonly bacterial (e.g., Campylobacter) infections. (B) The deep gray nuclei (particularly the thalami) are involved in 60% of patients with ADEM. These structures are involved less commonly in multiple sclerosis. (C) Only 25% of ADEM lesions show contrast enhancement. There usually is no mass effect except for cases of tumefactive demyelination, which also may be accompanied by a leading edge of restricted diffusion.
39
A 5-year-old boy with visual and hearing deficits and loss of developmental milestones presents for evaluation. MRI of the brain shows occipitoparietal periventricular demyelination with a leading edge of enhancement. What is the patient’s likely diagnosis? A. Adrenoleukodystrophy B. Canavan disease C. Alexander disease D. Krabbe disease E. Pelizaeus-Merzbacher disease
A. Adrenoleukodystrophy ## Footnote The presentation and imaging findings are consistent with X-linked adrenoleukodystrophy. This disease typically occurs in 4- to 6-year-old boys and is caused by mutations in the ABCD1 gene, leading to accumulation of very long chain fatty acids. Death or progression to a vegetative state usually occurs 2 years after symptom onset. (B) ­Canavan disease is caused by mutations in the ASPA gene on chromosome 17. It results in macrocephaly, with imaging showing sequelae of white matter demyelination and signal abnormalities in the globi pallidi and thalami. (C) Alexander disease is caused by mutations in the GFAP gene on chromosome 17. It is characterized by demyelination that progresses from anterior to posterior. Patients have astrocytic Rosenthal fibers and macrocephaly. (D Krabbe disease results from mutations in the GALC gene on chromosome 14 and leads to the deficiency of galactocerebroside β-galactosidase. The condition most commonly is diagnosed between the third and sixth months of life. Imaging shows abnormalities in the white matter, basal ganglia, cerebellum, and corticospinal tracts. (E) Pelizaeus-Merzbacher disease is an X-linked recessive disorder characterized by oligodendrocyte dysfunction leading to hypomyelination. Patients usually are males and present with nystagmus, seizures, hypotonia, and ataxia. On MRI, there is diffuse T2 signal hyperintensity in the white matter due to hypomyelination (myelinated white matter is dark on T2 and bright on T1 sequences).
40
The spinal cord lesion in the T2-weighted MRI shown in this image is consistent with what disease process? A. Poliomyelitis B. Amyotrophic lateral sclerosis C. Guillain-Barré syndrome D. Subacute combined degeneration
D. Subacute combined degeneration ## Footnote Subacute combined degeneration can be caused by vitamin B12, copper, or vitamin E deficiencies. It results in an abnormal signal within the dorsal columns of the spinal cord in an inverse V-shaped configuration with variable involvement of the lateral columns. Abuse of nitrous oxide can produce the same syndrome through inactivation of vitamin B12. Neurosyphilis (tabes dorsalis) is also known to involve the dorsal columns. (A) Poliomyelitis may show an abnormal signal and enhancement of anterior horn cells as well as ventral roots of the cauda equina if accompanied by radiculitis. (B) Amyotrophic lateral sclerosis preferentially involves the anterior and lateral columns of the spinal cord, which may show increased T2 signal. (C) Guillain-Barré syndrome presents with preferential pial enhancement of the conus medullaris and dorsal roots of the cauda equina. It should not be associated with intramedullary signal abnormalities.
41
A brain MRI shows a small lesion in the pons that is slightly hyperintense on T2-weighted imaging and shows “brush-like” enhancement and signal dropout on gradient echo sequences. There is no surrounding edema. This lesion is consistent with what disease process? A. Demyelinating plaque B. Metastasis C. Cavernous malformation D. Capillary telangiectasia
D. Capillary telangiectasia ## Footnote The imaging description of this lesion and its location are characteristic of capillary telangiectasias. Low signal on gradient echo (GRE) sequences is thought to be related to slow flow and increased deoxyhemoglobin content. These lesions sometimes can have areas of gliosis, and they nearly always are asymptomatic and found incidentally. (A) A demyelinating plaque does not show the constellation of features described, which are characteristic of capillary telangiectasias. (B) Capillary telangiectasias should be differentiated from metastases. The latter usually have surrounding edema (except for small lesions) and do not show signal loss on GRE sequences unless they are hemorrhagic, melanotic, or calcified. (C) Cavernous malformations may show various signal intensities depending on the stage of their blood products. They typically are described as having a “popcorn” or “berry” appearance with a surrounding rim of hemosiderin.
42
Where is a type C carotid-cavernous fistula located according to the Barrow classification? A. Between meningeal branches of the external carotid artery and cavernous sinus B. Between meningeal branches of the internal carotid artery and cavernous sinus C. Directly between the cavernous internal carotid artery and cavernous sinus D. Between meningeal branches of both the exter- nal and internal carotid arteries and cavernous sinus
A. Between meningeal branches of the external carotid artery and cavernous sinus ## Footnote Carotid cavernous fistulas can be direct or indirect. Direct fistulas (Barrow type A) develop between the cavernous internal carotid artery and cavernous sinus and are therefore high flow. They are more frequent in younger males and occur secondary to trauma or rupture of a cavernous internal carotid aneurysm. Types B, C, and D occur between meningeal branches of the internal or external carotid arteries, are slow flow, and are most frequently seen in women older than 50 years of age. A type C carotid cavernous fistula occurs between meningeal branches of the external carotid artery and cavernous sinus. (B) A Barrow type B fistula occurs between meningeal branches of the internal carotid artery and cavernous sinus. (C) A Barrow type A fistula occurs directly between the cavernous internal carotid artery and cavernous sinus. (D) A Barrow type D fistula occurs between meningeal branches of both the external and internal carotid arteries and cavernous sinus.
43
What is a characteristic of the lesion depicted in the MRI shown in these images? A. Lined by arachnoid cells resulting in accumulation of cerebrospinal fluid B. Most are intraventricular C. Show complete signal suppression on MR FLAIR sequences D. Usually show areas of patchy enhancement E. Associated with a risk of malignant transformation
E. Associated with a risk of malignant transformation ## Footnote T2, FLAIR, and diffusion-weighted imaging (DWI) MRI sequences are presented showing an epidermoid cyst. These lesions are characterized by very bright DWI signal (presumably a combination of restricted diffusion and T2 shine-through effect), lack of contrast enhancement, and nonsuppression on FLAIR. Epidermoid cysts arise from ectodermal inclusions during neural tube closure and rarely can degenerate into squamous cell carcinomas. (A) Arachnoid cysts and not epidermoid cysts are lined by arachnoid cells, resulting in accumulation of cerebrospinal fluid. (B) Up to 50% of epidermoid cysts are located in the cerebellopontine angle, although they uncommonly may arise within the ventricles. (C) Although signal in epidermoid cysts may resemble cerebrospinal fluid on T2, they do not suppress on FLAIR as demonstrated in the second image. The signal of epidermoid cysts on FLAIR sometimes has been described as “dirty” appearing and used to be the main imaging discriminator for diagnosis before DWI was available. This is in contradistinction to arachnoid cysts, which do suppress on FLAIR and follow cerebrospinal fluid signal on all sequences. (D) Although there sometimes can be minimal marginal contrast enhancement, epidermoid cysts should not show patchy or any significant enhancement, which would be suspicious for malignant transformation.
44
A 12-year-old boy presented to the emergency department with progressive headaches, nausea, and vomiting. Axial T2 and contrast-enhanced T1- weighted imaging and apparent diffusion coefficient maps are shown in these images. What is the patient’s likely diagnosis? A. Medulloblastoma B. Ependymoma C. Pilocytic astrocytoma D. Hemangioblastoma E. Metastasis
C. Pilocytic astrocytoma ## Footnote A well-circumscribed cystic mass with an avidly enhancing mural nodule in the cerebellum most likely is a juvenile pilocytic astrocytoma in a patient of this age, which has a peak incidence between 5 and 15 years of age. Despite its classification as WHO grade I, a pilocytic astrocytoma shows avid contrast enhancement of the solid components and paradoxically may exhibit aggressive-appearing imaging characteristics, with a metabolite pattern mimicking a high-grade lesion on MR spectroscopy (increased choline, decreased N-acetylaspartate, and increased lactate) and increased metabolism on 18F-fluorodeoxyglucose PET studies. A pilocytic astrocytoma most commonly occurs in the cerebellum followed by the optic nerve and chiasm (particularly when syndromic in neurofibromatosis type 1) and around the third ventricle and hypothalamus. It is a slow-growing tumor and most commonly presents with manifestations of increased intracranial pressure (such as in this case where there is hydrocephalus) and cerebellar signs. (A) Medulloblastomas usually occur in patients younger than 5 years of age but may be seen in older individuals. They have low apparent diffusion coefficient (ADC) values, and therefore appear dark on the ADC maps (in contrast to this case, where the solid component of the tumor is bright). Medulloblastomas arise from the superior medullary velum and fill the fourth ventricle rather than displace it. (B) Ependymomas arise from the floor of the fourth ventricle and fill it rather than displace it, in contrast to the tumor of this case. Ependymomas characteristically extrude through the ventricular outflow tracts into the foramen magnum and posterior fossa with a “plastic” or “toothpaste” appearance. They also tend to be seen in younger patients with a peak incidence between 1 and 5 years of age, although there is a smaller peak in young adults later in life. Cystic changes would be an unusual finding in ependymomas. (D) Hemangioblastomas more commonly present in adults and are rare in children unless they are syndromic (peak at 40 to 60 years of age). They also can present as a cystic mass with an enhancing mural nodule that typically abuts the pial surface, and they often have prominent flow voids due to hypervascularity. They may be associated with von Hippel–Lindau syndrome, but most are sporadic. (E) Some metastases may present with cystic changes, particularly from squamous cell primaries such as in head and neck, lung, and cervical cancers. Metastases, in general, are the most common cerebellar tumor in adults. They would be unexpected in a patient of this age
45
A 74-year-old woman presents to the emergency room complaining of vertigo and nausea increasing in severity over the past several hours. CT and MRI studies were performed, and representative images are shown here. This lesion likely represents a(n): A. Primary neoplasm B. Acute infarction C. Metastatic disease D. Arachnoid cyst E. Epidermoid cyst
B. Acute infarction ## Footnote Noncontrast CT and diffusion-weighted images are presented, and the distribution of the abnormality and presence of restricted diffusion are most compatible with an acute posterior inferior cerebellar artery (PICA) territory infarct. PICA infarcts may be associated with significant mass effect in the posterior fossa and herniation with rapid deterioration and death. Although they can present with specific neurologic syndromes (such as lateral or medial medullary syndromes), symptoms can be vague and nonspecific, and sometimes may be confused with labyrinthitis or gastroenteritis. (A) Hemorrhagic or high-grade primary neoplasms may result in areas of restricted diffusion due to blood products or high cellularity, respectively; however, they would be expected to be more heterogeneous and would not preserve the cerebellar architecture as in this case (note that some of the folia still can be defined on the diffusion image). Additionally, the vascular distribution of the abnormality and the evolution of symptoms over a few hours are compatible with a PICA territory infarct. (C) Approximately 50% of intracranial metastases may be solitary; however, findings in this case argue against a metastatic lesion. (D) Although the lesion presented is hypodense on CT, it is intraaxial and demonstrates restricted diffusion, both of which rule out an arachnoid cyst. (E) Epidermoid cysts can show restricted diffusion, and some can be intra-axial; however, in this case, the vascular distribution is characteristic of a PICA infarct.
46
A man who was found lying on the ground underwent an emergent CT of the head, shown in these images. What is the likely diagnosis? A. Ruptured cerebral aneurysm B. Acute arterial infarction C. Global anoxic injury D. Venous thrombosis
C. Global anoxic injury ## Footnote This is a case of diffuse cerebral edema/global anoxic injury. The noncontrast head CT shows effacement of the cerebral sulci, small ventricles, loss of the gray matter–white matter distinction, lack of definition of the deep gray nuclei, and effacement of the basal cisterns. (A) A ruptured intradural cerebral aneurysm would result in subarachnoid hemorrhage. The hyperdense appearance of the suprasellar cistern in this case often is referred to as “pseudosubarachnoid hemorrhage” and is due to the relative hypodensity of the swollen brain parenchyma and cisternal effacement. (B) Acute arterial infarction would lead to edema and mass effect in a territorial distribution. (D) Venous thrombosis may or may not result in ischemia that sometimes can become hemorrhagic. Findings that can be seen on CT include a hyperdense clot within the dilated vein (cord sign), cortical/subcortical edema (when cortical veins are involved), and deep gray matter edema (when deep draining veins are involved and often occurring bilaterally).
47
A young woman underwent an MRI study, shown in these images. What tumor is she at risk of developing? A. Glioma B. Meningioma C. Ependymoma D. Endolymphatic sac tumor E. Subependymal giant cell tumor
A. Glioma ## Footnote This is a case of neurofibromatosis type 1. The provided images show dysplasia of the left sphenoid bone with ipsilateral proptosis as well as a diffuse, nodular, and trans-spatial lesion involving the left head, face, neck, and parapharyngeal tissues compatible with plexiform neurofibromata. A central T2 dark spot may be seen within some of these lesions (the “target sign”) and is considered highly suggestive of neurofibromas. Approximately 15% of children with neurofibromatosis type 1 develop optic nerve gliomas, and they are also at an increased risk of developing gliomas in other regions of the brain. In addition, 4% of patients with neurofibromatosis type 1 develop peripheral malignant nerve sheath tumors. (B, C) Multiple inherited schwannomas, meningiomas, and ependymomas (MISME syndrome) are features of neurofibromatosis type 2 and not type 1. (D) Endolymphatic sac tumors are very rare neoplasms that can occur sporadically and have been reported to develop in 10 to 15% of patients with von Hippel–Lindau syndrome. (E) Almost all subependymal giant cell tumors are seen in the setting of tuberous sclerosis.
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What factor favors an epidural versus a subdural empyema? A. Restricted diffusion B. Crescentic shape C. Crosses sutures D. Less common cerebral edema E. Peripheral enhancement
D. Less common cerebral edema ## Footnote Epidural empyemas are associated less frequently with cerebral edema due to the presence of thick intervening dura between the collection and the brain. (A) Both epidural and subdural hematomas show restricted diffusion. (B) Similar to subdural hematomas, a crescentic shape is more consistent with a subdural hematoma, whereas epidural collections characteristically have a biconvex or lenticular shape. Note that subdural empyemas and hematomas sometimes can show a lenticular shape particularly if they are loculated. (C) Epidural collections including empyemas and hematomas do not cross sutures due to the firm dural attachments at these sites. (E) Both subdural and epidural empyemas enhance peripherally
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A mass, shown in this image, was discovered in a 29-year-old woman presenting with progressive bitemporal hemianopsia and hyperprolactinemia. Immunohistochemistry and electron microscopy following resection demonstrated chromophobic tumor cells and “misplaced exocytosis” with extrusion of secretory granules. What neuroimaging feature is highly suggestive of cavernous sinus invasion? A. Extension beyond the lateral intercarotid line B. Carotid encasement greater than 180 degrees C. Obliteration of the superior venous compartment D. Obliteration of the inferolateral venous compartment
A. Extension beyond the lateral intercarotid line ## Footnote measured on coronal images, is highly suggestive of cavernous sinus invasion by a pituitary adenoma with a positive predictive value of 85%. Other findings include obliteration of the carotid venous sulcus compartment (the space between the sphenoid bone and the ipsilateral cavernous internal carotid artery) with a positive predictive value of 95% and internal carotid artery encasement of ≥ 67% (about 240 degrees) with a positive predictive value of 100%. (B) Carotid encasement of ≥ 67% has been associated with the highest likelihood of ipsilateral cavernous sinus invasion. (C) Obliteration of the superior venous compartment is not significantly associated with cavernous sinus invasion. (D) Obliteration of the inferolateral venous compartment is not significantly associated with cavernous sinus invasion.
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What is a characteristic of the lesion depicted in this angiogram? A. Fibromuscular dysplasia predisposes to an increased risk of direct-type lesions. B. Spontaneous intracranial hemorrhage is the most common presentation. C. Dural-type lesions commonly present with a subjective bruit. D. A majority of direct-type lesions result from venous thrombosis. E. Dural-type lesions most commonly present in young males.
A. Fibromuscular dysplasia predisposes to an increased risk of direct-type lesions. ## Footnote The angiogram shows early opacification of the cavernous sinus compatible with a carotid cavernous fistula. This is most evident on the left side, where the ophthalmic vein also can be seen. These lesions result from either a direct communication between the carotid artery and cavernous sinus (direct or high-flow fistulas; Barrow type A) or between the cavernous sinus and dural branches of the internal carotid artery, external carotid artery, or both (indirect, low flow, and dural fistulas; Barrow types B, C, and D, respectively). Other than trauma and aneurysmal rupture, conditions associated with direct carotid cavernous fistulas include fibromuscular dysplasia, Ehlers-Danlos syndrome, and pseudoxanthoma elasticum. (B) Spontaneous parenchymal or subarachnoid hemorrhage can be seen in direct fistulas, particularly when there is retrograde cortical venous flow, and occurs in about 5% of cases. Bruits and visual manifestations are much more common. (C) Direct (not dural type) fistulas commonly present with a subjective bruit (about 85% of cases) that sometimes also may be auscultated. (D) Venous thrombosis is a known mechanism in the development of some carotid cavernous fistulas; however, by far the most common etiologies of direct fistulas are trauma and aneurysm rupture. (E) Dural fistulas most commonly present in middle-aged and elderly women. Traumatic direct fistulas are more common in young males.
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The tumor depicted in the MRI shown in these images demonstrated microcysts and mild pleomorphism on histological examination and stained positive for glial fibrillary acidic protein, neuronspecific enolase, and neuronal cell adhesion molecule. What is true about this lesion? A. Associated with a high recurrence rate B. Presents most commonly in young adults C. Frequently complicated by hemorrhage D. Associated with TSC-1 and TSC-2 gene mutations E. Usually shows minimal to no contrast enhancement
E. Usually shows minimal to no contrast enhancement ## Footnote Subependymomas are benign, slow-growing neoplasms classified as WHO grade I. They typically show minimal to no contrast enhancement; however, this is variable, as some subependymomas may enhance more prominently, particularly those located in the fourth ventricle. They may have microcystic changes (both on histological examination and on MRI), are well circumscribed, are noninvasive, and may contain foci of calcification. The classic location in the fourth ventricle is at the obex, although they can occur anywhere in the ventricular system. (A) Subependymomas are highly resectable neoplasms. Recurrence is rare and usually related to incomplete excision. (B) Subependymomas present most commonly in middleaged and elderly adults, with a peak incidence in the fifth and sixth decades of life. Symptomatic patients may present earlier with signs of intracranial hypertension. (C) Hemorrhage may occur with subependymomas, but it is a rare event. (D) Subependymomas are not associated with TSC-1 or TSC-2 mutations, in contrast to the subependymal giant cell astrocytomas of tuberous sclerosis.
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What is a feature of the focal areas of signal intensity (FASI) or unidentified bright objects (UBOs) in neurofibromatosis type 1? A. They are most common in basal ganglia and dentate nuclei. B. They are premalignant lesions. C. A small proportion show contrast enhancement. D. The presence of mass effect is characteristic.
A. They are most common in basal ganglia and dentate nuclei. ## Footnote The focal areas of signal intensity (FASI) or unidentified bright objects (UBOs) are thought to represent myelin vacuolization in patients with neurofibromatosis type 1. They are most common in the basal ganglia, dentate nuclei, and brainstem. (B–D) These lesions are not premalignant, and many regress in adulthood. They do not show contrast enhancement or mass effect, the presence of which should raise concern about a glioma.
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What MRI sequence specifically should be included to evaluate a patient with suspected cerebral abscess? A. Susceptibility weighted B. Diffusion weighted C. Time of flight D. Constructive interference in steady state (CISS) E. FLAIR
B. Diffusion weighted ## Footnote The two most important sequences in the evaluation of a cerebral abscess are contrast-enhanced T1-weighted sequences and diffusion-weighted imaging (DWI). An abscess usually shows a relatively smooth and homogeneous enhancing wall that often (but not always) is thicker on the side of the gray matter and thinner toward the ventricles and white matter. Pus within an abscess almost always shows prominent restricted diffusion, which is reflected as bright signal on DWI and corresponding dark signal on apparent diffusion coefficient (ADC) maps. (A) Susceptibility-weighted imaging (SWI) is a gradient echo–based technique that is exquisitely sensitive for the detection of paramagnetic and diamagnetic substances such as ferritin, calcium, hemosiderin, and deoxyhemoglobin. The capsule of an abscess may appear dark on SWI or T2, presumably due to the presence of paramagnetic free radicals within macrophages. (C) Time of flight is an MR angiography technique that does not routinely require the administration of contrast material and is based on the flowrelated enhancement of spins entering an imaging slice in one direction. (D) Constructive interference in steady state (CISS) is an MRI technique that is based on consecutive steady-state free precession (SSFP) sequences. It produces images that have very high T2 signal and therefore excellent contrast between fluid and parenchyma. (E) Fluidattenuated inversion recovery (FLAIR) is a pulse sequence that uses an inversion recovery technique to null the signal of simple fluid.
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A 74-year-old man underwent a CT study of the chest, which demonstrated the lesion shown in these images. This lesion is compatible with what diagnosis? A. Metastasis B. Paget disease C. Hemangioma D. Plasmacytoma
C. Hemangioma ## Footnote These CT images show the characteristic imaging features of a vertebral hemangioma with vertical trabeculations on the sagittal image and a corresponding “polka dot” appearance on the axial image. Note the preservation of the cortex despite the presence of the trabeculations; however, also remember that hemangiomas can be aggressive and may present with extraosseous soft tissue extension and mass effect on the spinal cord or nerves. On MRI, they usually are bright on both T1 and T2 sequences due to the presence of a fatty stroma, although atypical (predominantly vascular) hemangiomas may be dark on T1 and simulate metastases. Approximately 30% of hemangiomas are multiple. (A) Metastasis would result in variable degrees of marrow replacement and osseous destruction without the vertical trabecular pattern of a hemangioma. (B) Paget disease is associated with expansion of the bone; in the spine, the involved vertebra often appears larger than the ones above and below it. Paget disease also presents with cortical thickening and would not show a uniform, vertical trabecular pattern. (D) Plasmacytomas cause osseous destruction and do not respect the trabeculae.
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A 67-year-old man with left L5 radiculopathy underwent MRI of the lumbar spine, shown in this image. This lesion likely represents a(n): A. Extruded disk B. Synovial cyst C. Ligamentum flavum hypertrophy D. Uncovertebral joint hypertrophy
B. Synovial cyst ## Footnote The axial T2 image shows a well-circumscribed, cystic-appearing, extradural mass, with its base along a degenerated and hypertrophied left facet joint, which is compatible with a synovial cyst. In this case, the cyst impinges on the left descending nerve roots, which explains the patient’s symptoms. The morphology of the cyst and its anatomic relationship with a degenerated facet joint are more important than the signal of its contents, which may vary depending on the presence of hemorrhage or proteinaceous material. Synovial cysts can contain gas, and their walls may show enhancement or calcification. They most commonly develop in patients older than 60 years of age and are more common in females; 90% occur in the lumbar spine. (A) In this case, the open base of the lesion is centered along the facet rather than the disk, and the T2 bright contents also seem to communicate with the facet joint. Additionally, the lesion has a convex, well-circumscribed margin anteriorly. These features make a synovial cyst the right diagnosis; however, note that disk material can separate from the parent disk and migrate virtually anywhere within the epidural space. (C) Cysts also can originate from the ligamenta flava; however, the lesion in this case is centered along the facet joint. (D) The uncovertebral joints form between the uncus and uncinate processes of the cervical spine between C3 and C7. There are no uncovertebral joints in the lumbar spine. Additionally, hypertrophied bone and osteophytes would look dark on T2 and not bright as in this lesion.
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What is true regarding the lesion indicated by the arrow in the contrast-enhanced T1-weighted MRI shown in this image? A. It is usually angiographically occult. B. It is composed of radially arranged medullary veins emptying into a dilated draining vein. C. High flow from shunting may result in flowrelated aneurysms. D. A larger nidus is associated with an increased surgical risk.
B. It is composed of radially arranged medullary veins emptying into a dilated draining vein. ## Footnote This image shows radially arranged medullary veins in a “caput medusae” configuration emptying into a dilated draining vein compatible with a developmental venous anomaly (also known as a venous angioma). These lesions usually are benign and constitute an incidental finding in the majority of cases, although rarely they may thrombose. Some reports have described seizures, headaches, and hemorrhage, but the association of venous angiomas and these manifestations has not been established firmly. Approximately 20 to 30% of these lesions are associated with cavernous malformations, which may explain symptoms in at least some cases. The majority of developmental venous anomalies are isolated, but they also can be multiple particularly when associated with the blue rubber bleb nevus syndrome. Blood oxygen level dependent (BOLD) imaging sequences, such as susceptibility-weighted imaging (SWI), are the preferred modality for their detection, as these lesions may be missed on other sequences due to their slow flow. (A) Developmental venous anomalies have a characteristic appearance on angiography, showing exclusive enhancement in the venous phase, although sometimes a faint blush may be evident in the late arterial phase. Angiographically occult vascular lesions include capillary telangiectasias and cavernous malformations. (C) High flow from shunting may result in flow-related aneurysms in arteriovenous malformations. There is no arteriovenous shunting in developmental venous anomalies. (D) A larger nidus is associated with an increased surgical risk in arteriovenous malformations and upgrades these lesions in the SpetzlerMartin grading system.
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A patient presents to clinic for follow-up after suffering from a nontraumatic retinal detachment. The lesion shown in these images is found on a subsequent MRI. The patient should be screened for: A. Lisch nodules B. Bilateral vestibular schwannomas C. Subependymal giant cell astrocytoma D. Renal cell carcinoma E. Low levels of serum ceruloplasmin
D. Renal cell carcinoma ## Footnote The MRI shows a heterogeneously enhancing destructive lesion in the left petrous bone. There are areas of intrinsic T1 hyperintensity secondary to hemorrhage, proteinaceous contents, or cholesterol. The appearance and location are suggestive of an endolymphatic sac tumor, particularly in a patient presenting with spontaneous retinal detachment, which may be seen in von Hippel–Lindau (VHL) syndrome due to hemorrhage from retinal capillary hemangioblastomas; 15% of patients with VHL develop an endolymphatic sac tumor, and 40 to 70% of them ultimately develop renal cell carcinoma, the incidence of which increases with age. (A) Lisch nodules are the most common ocular lesions in neurofibromatosis type 1. They are not associated with VHL syndrome. (B) Bilateral vestibular schwannomas are diagnostic of neurofibromatosis type 2. (C) Subependymal giant cell astrocytomas occur in patients with tuberous sclerosis complex secondary to mutations in the TSC-1 or TSC-2 genes, although isolated tumors rarely have been described. These tumors are not associated with VHL. (E) Low levels of serum ceruloplasmin result in an abnormal accumulation of copper in Wilson disease.
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What is a characteristic of the condition depicted in the T2-weighted MRI shown in this image? A. Lined by dysplastic white matter B. Frequently accompanied by microcephaly and other cerebral anomalies C. Lined by endodermal endothelium D. May show variable signal intensities depending on its contents E. Results from a bilateral vascular insult to the anterior cerebral circulation in utero
B. Frequently accompanied by microcephaly and other cerebral anomalies ## Footnote This is a case of “open lip” (type 2) schizencephaly, which may result from a variety of insults in utero (including infection and ischemia) that affect the germinal zone during cortical development and lead to abnormal neuronal migration. There also has been an association with COL4A1 and COL4A2 mutations. Schizencephaly manifests as a transmantle cleft lined by dysplastic gray matter (not white matter) that connects the subarachnoid space with the ventricular system (pia to ependyma). It has been associated with various anomalies including gray matter heterotopia, polymicrogyria, absence of the septum pellucidum, and frontal lobe dysplasia. Approximately 80% of cases are “open lip” and the rest are “closed-lip.” (A) Schizencephaly is lined by dysplastic gray matter and not white matter, as would be the case in porencephalic cysts. (C) Schizencephaly is lined by dysplastic gray matter and not endodermal endothelium, which would be the case in a neurenteric cyst. (D) A schizencephalic cleft openly communicates with the subarachnoid and intraventricular spaces, and therefore follows cerebrospinal fluid signal on all sequences. Cysts with proteinaceous (e.g., neurenteric cysts) or hemorrhagic contents may show variable signal intensities. (E) A bilateral vascular insult to the anterior and middle cerebral arteries in utero would lead to hydranencephaly and destruction of parenchyma in these territories with preservation of the posterior circulation; however, large bilateral schizencephaly with hydrocephalus may be difficult to differentiate from hydranencephaly. Some authors suspect that they may be part of a continuum.
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A 12-year-old boy with progressive headaches and lower cranial nerve palsies underwent an MRI scan, shown in these images. Which is the likely diagnosis? A. Chondrosarcoma B. Chordoma C. Nasopharyngeal carcinoma D. Meningioma E. Lymphoma
B. Chordoma ## Footnote Skull base chordomas most commonly present in patients between 20 and 40 years of age, but 16% occur in patients younger than 18 years of age. Location in the lower clivus with associated osseous erosion is typical. On MRI, they demonstrate very bright T2 signal, presumably related to mucinous contents along with thin T2 dark fibrous septations. They show moderate to marked enhancement often along the septations in a “honeycomb” configuration. Skull base chordomas carry a poor prognosis, worse than that for chondrosarcomas. (A) Chondrosarcomas have imaging features similar to those for chordomas, but they more often occur off midline and centered at the petroclival fissure, and may be accompanied by calcified chondroid matrix. Chondrosarcomas are unusual at this age. (C) Nasopharyngeal carcinoma is rare at this age; it would have a more infiltrative appearance, and it is not as bright on T2 sequences. Additionally, the nasopharyngeal mucosa is preserved in this case, and the tumor is centered at the skull base, resulting in anterior deviation of the prevertebral muscles as seen on the axial images. (D) Meningiomas can invade bone but tend to do so more diffusely. They also are not as bright on T2 sequences (unless there are areas of degeneration) and tend to show more homogeneous enhancement without the honeycomb appearance of this case. They are rare in children unless associated with a syndrome. (E) Lymphoma can arise from lymphoid tissue in the nasopharynx and extend to the skull base; however, the nasopharyngeal mucosa in this case is preserved. Lymphoma also usually enhances more avidly and homogeneously.
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A man presented with dysfunction of the left cranial nerves V and VI. T1- and T2-weighted MRI and the corresponding apparent diffusion coefficient (ADC) map are shown in these images. What is the patient’s likely diagnosis? A. Cholesterol granuloma B. Cholesteatoma C. Trapped secretions within pneumatized petrous cells D. Trigeminal schwannoma
A. Cholesterol granuloma ## Footnote This is a well-circumscribed, expansile lesion centered in the left petrous apex. It does not enhance, and it shows intrinsic T1 brightness as well as T2 dark material within it, corresponding to blood products. There is no restricted diffusion as demonstrated by increased signal on the apparent diffusion coefficient (ADC) map. Findings are compatible with a cholesterol granuloma. These are benign lesions related to repeated middle ear infections. They contain cholesterol crystals, lipids, and fluid and are prone to recurrent hemorrhage. Cholesterol granulomas can occur anywhere in the temporal bone where there are mucosa-lined aerated cells, and rarely have been reported in the paranasal sinuses. (B) Cholesteatomas can occur in this location but show restricted diffusion (they would be dark on ADC and bright on diffusionweighted imaging) and usually are not bright on T1. (C) Trapped secretions within pneumatized petrous cells sometimes can show intrinsic T1 brightness due to proteinaceous contents, but they would not result in an expansile mass. The normal trabeculae should be preserved, although this is difficult to visualize on MRI. (D) A trigeminal schwannoma would show enhancement and would follow the course of the cranial nerve sometimes with involvement of the Meckel cave.
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What is the likely mechanism that caused the injury shown in this image? A. Lateral bending and compression B. Axial rotation C. Abrupt extension D. Axial loading E. Flexion and distraction
E. Flexion and distraction ## Footnote The sagittal CT image shows a compression fracture involving a midthoracic vertebra with a fracture line extending posteriorly across the spinous process above. This is consistent with a Chance fracture, which features a horizontal fracture orientation through the entire spinal column and is a result of a flexion and distraction injury. These fractures usually are associated with lap belts. Neurologic injury is rare, but there is an increased frequency of intra-abdominal injuries. Up to 25% of Chance fractures may be purely ligamentous. (A) Extreme lateral bending can result in a lateral compression fracture or, potentially, a fracture of the transverse processes. Avulsion fractures of the transverse processes in the lumbar spine also can occur due to abrupt contraction of the psoas muscles. (B) Axial rotation can lead to facet dislocations, particularly in the cervical spine. (C) Abrupt extension of the neck can disrupt the anterior longitudinal ligament and result in an extension teardrop fracture, which is an unstable injury. (D) Axial loading can lead to burst or compression fractures of the anterior column if the injury occurs during flexion.
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A 37-year-old man who is an intravenous drug user presented with headaches. An MRI of the brain was performed, shown in these images. What is an additional expected imaging finding? A. Presence of lactate and amino acids on MR spectroscopy B. Hyperintense capsule on T2 sequence C. Increased apparent diffusion coefficient values in the center of the lesion D. High relative cerebral blood volume ratio in the capsule relative to white matter
A. Presence of lactate and amino acids on MR spectroscopy ## Footnote The images in this case show an intra-axial lesion with peripheral enhancement and increased signal on diffusion-weighted imaging (DWI). Although apparent diffusion coefficient (ADC) maps are not presented, the degree of brightness in the center of the lesion on DWI is high enough that this is expected to represent restricted diffusion and would therefore look dark on ADC maps. These findings essentially are diagnostic of an abscess; a few rare cases of necrotic metastases with central restricted diffusion have been reported. Abscesses can show various amino acids on MR spectroscopy, including alanine, valine, leucine, and succinate as well as lactate and lipid peaks. Of note, necrotic primary or metastatic tumors also may show lactate and lipid peaks. (B) The capsule of a cerebral abscess usually is iso- to hypointense on T2-weighted sequences. This is attributed to the presence of collagen, blood products, or free radicals generated by phagocytosing macrophages. (C) The necrotic center of an abscess demonstrates significant restricted diffusion that manifests as very bright signal on DWI and low ADC values. (D) The capsule of an abscess typically has lower relative cerebral blood volume (rCBV) relative to white matter. Glioblastomas, which may look similar to abscesses, have been associated with high rCBV ratios in the capsule.
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A 75-year-old man underwent a CT scan of the head. Representative images are shown here. What is the patient’s likely diagnosis? A. Multiple myeloma B. β-thalassemia C. Prostate cancer metastases D. Paget disease
D. Paget disease ## Footnote The etiology of Paget disease is not entirely certain. Its hallmark is excessive bone remodeling and overgrowth and is defined by three stages: lytic, mixed, and sclerotic. The spine and skull are the most common sites of involvement followed by the pelvis. The presence of pain or focal destructive lesions on imaging should raise concern for sarcomatous degeneration. (A) Multiple myeloma characteristically shows numerous lucent (lytic) lesions throughout the calvaria that may result in a “punched out” appearance. (B) Bone marrow hyperplasia in β-thalassemia can lead to significant skull thickening often showing a so-called hair-on-end appearance. It would not produce the lucent and sclerotic pattern of this case. (C) Prostate cancer metastases typically are osteoblastic (sclerotic) and can be diffuse; however, they do not result in the mixed lytic/sclerotic geographic pattern of this case. Note on the provided images that, despite the diffuse involvement of the calvaria, the inner and outer tables are relatively preserved.
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The digital subtraction angiogram shown here depicts a(n): A. Middle cerebral artery/anterior cerebral artery bifurcation aneurysm B. Posterior communicating artery aneurysm C. Basilar tip aneurysm D. Ophthalmic artery aneurysm
B. Posterior communicating artery aneurysm ## Footnote The image shown is a lateral projection of a digital subtraction angiogram following a carotid artery injection. It shows a vascular outpouching projecting posteriorly from the dorsal aspect of the C7 (communicating or terminal) segment of the internal carotid artery at the expected origin of the posterior communicating artery. Aneurysms in this location represent about 30% of all ruptured intracranial aneurysms and may result in intraparenchymal hemorrhage, typically in the mesial temporal lobe. Patients may present with subarachnoid hemorrhage or a third cranial nerve palsy due to mass effect. (C) This is a carotid injection and thus does not depict the posterior circulation and basilar tip. (D) The ophthalmic artery arises from the C6 (ophthalmic or supraclinoid) segment of the internal carotid artery and projects anteriorly.
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A 53-year-old man is status post–glioblastoma resection and radiation therapy with concomitant temozolomide. A brain MRI shows an increasing enhancing lesion. What neuroimaging finding would favor the presence of recurrent tumor over radiation necrosis/pseudoprogression? A. Increased apparent diffusion coefficient (ADC) values B. Increased relative cerebral blood volumes C. “Cut green pepper” appearance D. Decreased FDG uptake on PET
B. Increased relative cerebral blood volumes ## Footnote Studies have shown that recurrent tumor has a higher relative cerebral blood volume (rCBV) normalized to the contralateral white matter compared with radiation necrosis, although there is some overlap. rCBV values greater than 2.6 have been suggested as a cutoff for the presence of recurrent tumor, and values lower than 0.6 suggest pseudoprogression. (A) Several studies show that recurrent tumor tends to have lower apparent diffusion coefficient (ADC) values compared with radiation necrosis. ADC ratios related to the contralateral white matter appear to be more accurate than absolute ADC values. (C) A “cut green pepper,” “soap bubble,” or “Swiss cheese” appearance has been described in radiation necrosis, although this usually does not allow reliable discrimination between these processes. (D) Decreased FDG uptake on PET favors radiation necrosis. False negatives may occur in the presence of a large area of necrosis.
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A 48-year-old woman with a history of HIV underwent a brain MRI, shown in this image. The MRI findings are consistent with: A. Lymphoma B. Progressive multifocal leukoencephalopathy C. HIV encephalopathy D. Cerebritis
C. HIV encephalopathy ## Footnote HIV encephalopathy is the most common central nervous system infection related to the HIV virus. Although the incidence of frank dementia has decreased substantially following the advent of highly active antiretroviral therapy, the prevalence of mild to moderate cognitive deficits in this population has increased and probably is at least partially related to longer survival. Note the prominent cerebral volume loss for the patient’s age, lack of mass effect, and symmetric confluent white matter signal abnormalities that spare the U fibers. (A) Lymphoma would have some degree of mass effect and would be more focal than the image demonstrates. Lymphoma in patients with HIV/ AIDS commonly has central necrosis, whereas lymphoma occurring in the nonimmunocompromised population is diffusely solid and enhances homogeneously. (B) Progressive multifocal leukoencephalopathy usually is bilateral but asymmetric. When there are subcortical signal abnormalities, they virtually always involve the U fibers; note that these are spared in this case and are seen as dark gray bands between the cortex and the bright white matter lesions. (D) Cerebritis would present with variable degrees of gray and white matter edema.
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What MRI sequences are necessary for the evaluation of Hirayama disease? A. Gradient echo sequences B. Delayed contrast sequences C. Diffusion-weighted sequences D. Flexion/extension sequences
D. Flexion/extension sequences ## Footnote Flexion/extension sequences are important in the evaluation of Hirayama disease (monomelic amyotrophy), as they would demonstrate detachment and anterior displacement of the dura on neck flexion, with resultant spinal cord compression and myelopathy. Hirayama disease is a benign and self-limiting disease that usually occurs in patients between 15 and 25 years of age. (A) Gradient echo sequences in the spine are useful to differentiate disks from osteophytes and to demonstrate foci of hemorrhage within the cord. These sequences also are less prone to cerebrospinal fluid pulsation artifact. (B) Routine postcontrast sequences help delineate the enhancing epidural space in Hirayama disease and may facilitate identification of the dura. Delayed contrast sequences are not particularly helpful. (C) Diffusion-weighted sequences are technically difficult to acquire in the spine. They may be useful in the evaluation of acute spinal cord ischemia and spinal infection.
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A 45-year-old immigrant presents with a several month history of back pain and malaise. There is no history of fever. An MRI was performed, shown in this image. What is the likely diagnosis? A. Pyogenic diskitis/osteomyelitis B. Tuberculous spondylitis C. Degenerative disk disease D. Osseous metastases
B. Tuberculous spondylitis ## Footnote Tuberculous spondylitis (also known as Pott disease) originates in the end plates and typically spreads in a subligamentous fashion to involve the adjacent vertebrae, frequently, but not always, sparing the intervertebral disks, as seen in this case. The provided contrast-enhanced T1 image shows a dark lesion (presumably fluid/pus) with peripheral enhancement. There also is enhancement of the adjacent vertebra above with preservation of the intervening disk. Tuberculous spondylitis has a higher incidence of extensive paraspinal abscess formation compared with pyogenic infections. Its onset tends to be insidious and gradual, which not uncommonly leads to a delayed diagnosis. Constitutional symptoms including fever and weight loss are seen in less than 40% of cases. (A) Pyogenic osteomyelitis typically involves the intervertebral disks. In children, infection is thought to start in the disks, with secondary involvement of the adjacent vertebrae. In adults, the disease is thought to start in the end plates, with involvement of the disks in the majority of cases. (C) Degenerative disk disease would be centered in the intervertebral disk spaces and may result in secondary degenerative changes in the adjacent end plates. (D) Osseous metastases usually enhance and tend to involve the pedicles and posterior elements. They would not show the cystic appearance of the larger lesion seen in the provided image.
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The presence of a “swirl” sign is described on a CT of the head. This finding indicates: A. Thrombosis B. Malignant transformation C. Acute extravasation D. Abscess formation
C. Acute extravasation ## Footnote The “swirl” sign is seen on noncontrast head CT and is defined as areas of low attenuation within an acute intracranial hematoma. It indicates freshly extravasated and unclotted blood and is associated with expansion of the hematoma and a worse prognosis. (A) Thrombosis can present as a hyperdense clot on noncontrast head CT or a filling defect following the intravenous administration of contrast material. (B) Malignant transformation can occur in various neoplasms. It is not associated with a “swirl” sign. (D) An abscess presents as a fluid collection with an enhancing wall and surrounding edema. MRI shows central restricted diffusion. It is not associated with a “swirl” sign.
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A coronal noncontrast CT reformat of a 35-yearold woman is shown in this image. What process is likely to be directly related to the represented disease? A. Cytokine release and production of mucopolysaccharides B. Hematogenous spread of poorly differentiated adenocarcinoma C. IgG4-positive lymphoplasmacytic infiltration D. Monoclonal B-cell population
A. Cytokine release and production of mucopolysaccharides ## Footnote Thyroid orbitopathy can affect any extraocular muscle, but the most typical presentation is that of involvement of the inferior, middle, and superior rectus muscles, which are markedly enlarged in this case. Involvement of the lateral rectus muscle almost never occurs in isolation. The pathophysiology is thought to be related to lymphocytic infiltration and cytokine release, which stimulates fibroblasts to produce mucopolysaccharides and, in turn, leads to soft tissue edema due to a hyperosmolar shift. (B) The most common primary tumors to metastasize to the orbit are breast, lung, prostate, and melanoma. It would be unusual for orbital metastases to result in this symmetric appearance of extraocular muscle enlargement. (C) IgG4-related disease of the orbit is being increasingly recognized as a cause of “idiopathic” inflammatory pseudotumor. It can be bilateral and involve any orbital structure, including the extraocular muscles, lacrimal sac, and optic nerve sheath complex. (D) Lymphoma may present as a soft tissue mass frequently related to the lacrimal gland or conjunctiva (MALT lymphoma). Other orbital structures also may be involved.
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What is an expected radiographic finding in tension pneumothorax? A. Ipsilateral diaphragmatic elevation B. Contralateral increased intercostal spaces C. “Deep sulcus” sign D. Mediastinal deviation to the contralateral side E. Tracheal deviation to the ipsilateral side
D. Mediastinal deviation to the contralateral side ## Footnote A tension pneumothorax is accompanied by shift of the mediastinal structures to the contralateral side due to a progressive mass effect. (A) The diaphragm typically is flattened and depressed on the side of the tension pneumothorax. (B) The ipsilateral (not contralateral) intercostal spaces increase secondary to increased intrathoracic volume and pressure on the side of the tension pneumothorax. (C) The “deep sulcus” sign may be seen in pneumothoraces on supine radiographs, as air collects basally and anteriorly rather than at the apex in an upright projection. It does not necessarily reflect a tension pneumothorax. (E) As with mediastinal structures, the trachea may be deviated to the contralateral side in tension pneumothorax.
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A CT of the lumbar spine shows a squared vertebra with a “picture frame” appearance. This finding is consistent with what disease process? A. Paget disease B. Vertebral hemangioma C. Lytic metastasis D. Blastic metastasis
A. Paget disease ## Footnote Paget disease is a disorder of uncertain etiology where there is excessive bone remodeling and overgrowth. It most commonly occurs in the spine, skull, and pelvis. In the osteosclerotic phase, there is cortical thickening and coarsening of the trabeculations, which often lead to expansion of the involved bone. In the spine, the vertebrae become squared, and a thick, sclerotic margin may be seen, resulting in the “picture frame” sign. (B) Vertebral hemangiomas can lead to increased vertical trabeculations that may be seen as dense dots on axial images. (C) Lytic metastases do not cause a “picture frame” appearance. (D) Blastic metastases can produce the “ivory vertebra” sign if they involve the entire vertebral body. Blastic metastases can be seen in various malignancies such as prostate and breast cancer, transitional cell carcinoma, and neuroendocrine tumors
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What structure is supplied by the arteries shown in this image (arrows)? A. Posterior limb of the internal capsule B. Anterior limb of the internal capsule C. Anteromedial caudate nucleus D. External capsule E. Thalamus
A. Posterior limb of the internal capsule ## Footnote The arrows point to the anterior choroidal arteries, which originate between the posterior communicating arteries and the carotid termination. The posterior communicating arteries can be seen immediately medial to these on the provided image. The anterior choroidal arteries supply the posterior limbs of the internal capsules, lateral geniculate nuclei, optic tracts and chiasm, hippocampi, amygdalae, and choroid plexus, among other structures. (B) The anterior limb of the internal capsule (lower half) is supplied by the recurrent artery of Heubner, which is a branch of the proximal anterior cerebral artery. The upper half is supplied by the lateral lenticulostriate arteries. (C) The anteromedial caudate nucleus as well as the anterior portion of the lentiform nucleus are supplied by the recurrent artery of Heubner. (D) The external capsule is supplied by the lateral lenticulostriate arteries, which are branches of the proximal middle cerebral artery and also supply the lateral aspect of the putamen and upper half of the internal capsule. (E) The various vascular territories of the thalamus all are supplied by branches of the posterior cerebral and posterior communicating arteries
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A 23-year-old man is brought to the emergency department following a high-velocity motor vehicle collision. An emergent CT of the cervical spine is shown in this image. What is a characteristic of this lesion? A. Uncommon in children B. High incidence of neurovascular injury C. Occurs secondary to axial loading D. May be identified by a basion-dental interval greater than 7 mm
B. High incidence of neurovascular injury ## Footnote The sagittal CT image shows too much space between the dens and tip of the clivus (basion– dens interval) consistent with atlanto-occipital dissociation. This is a severe craniocervical injury that results from sudden deceleration, with hyperflexion or hyperextension of the head, which disrupts the alar, cruciate, and apical ligaments and tectorial membrane. The condition is fatal in the great majority of patients secondary to a high incidence of neurovascular injury. (A) Atlanto-occipital dissociations are two to three times as common in children as in adults, presumably due to their relatively large head sizes, small size of their occipital condyles, and near horizontal orientation of the atlanto-occipital joints. (C) Other less severe injuries such as the Jefferson fracture may occur secondary to axial loading. (D) Atlanto-occipital dissociation injuries may be identified by a basion– dens interval greater than 12 mm as originally measured on lateral cervical spine radiographs. One study suggest a lower cutoff value (8.5 mm) with CT imaging, due to the presence of magnification on plain radiography.
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A 45-year-old woman with history of breast cancer underwent an MRI study of the brain. What is a common clinical manifestation of the process presented in these images? A. Meningismus B. Headache C. Ischemia D. Diabetes insipidus E. Dysarthria
B. Headache ## Footnote Leptomeningeal carcinomatosis occurs in about 5% of patients with metastatic cancer and portends a poor prognosis. Half of these patients present with headaches, which represent the most common clinical manifestation. The incidence of leptomeningeal carcinomatosis is four times higher in autopsy studies. (A) Meningismus is present in 13% of patients with leptomeningeal metastases. (C) Ischemia is an uncommon complication of leptomeningeal carcinomatosis. In contrast, tuberculosis can manifest with leptomeningeal disease that characteristically results in cerebral infarcts. (D) Diabetes insipidus can occur in patients with infundibular involvement but is much less common than headache. It also is more frequently seen in leukemic patients rather than in patients with solid tumor leptomeningeal disease. (E) Dysarthria is an uncommon complication that occurs in 7% of patients with leptomeningeal metastases.
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Axial noncontrast CT and T2-weighted MRI are shown in these images. What is the likely diagnosis? A. Langerhans cell histiocytosis B. Epidermoid C. Abscess D. Leptomeningeal cyst
D. Leptomeningeal cyst ## Footnote The CT shows a cyst-like structure projecting through a calvarial defect. The T2 image better demonstrates that there is encephalomalacia in area of the brain, and therefore findings are compatible with a leptomeningeal cyst. These findings develop from fractures with associated dural tears and herniation of the pia-arachnoid through the dural defect, with progressive osseous erosion (also known as a “growing” skull fracture) due to cerebrospinal fluid pulsations. (A) Langerhans cell histiocytosis is an important cause of a lytic calvarial defect in a child. Given the underlying encephalomalacia demonstrated, findings are more likely related to prior trauma. (B) An epidermoid can be primarily calvarial, but there is no evidence of it on the MRI shown in these images, which instead shows underlying encephalomalacia. (C) The T2 image demonstrates encephalomalacia and no evidence of an abscess or parenchymal edema. Additionally, an abscess would not result in a calvarial defect.
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A 48-year-old man underwent CT and MR studies after presenting with left-sided ophthalmoplegia. The lesion enhanced following the administration of intravenous contrast material and did not show restricted diffusion. Representative images are shown here. What is correct regarding this entity? A. Commonly produces a chondroid matrix B. Consists of granulation tissue and cholesterol crystals C. Represents trapped secretions within the petrous apex D. Arises from aberrant ectoderm within petrous apex cells E. Commonly demonstrates low apparent diffusion coefficient values
A. Commonly produces a chondroid matrix ## Footnote The CT image shows a destructive lesion involving the left petrous apex and petroclival junction, with contrast enhancement on the MRI study. There are small, calcific densities within it that could represent either chondroid matrix or eroded bone. Of the provided options, this lesion is most consistent with a chondrosarcoma, which comprises a heterogeneous group of malignant neoplasms characterized by the production of a chondroid matrix (sometimes seen as “rings” and “arcs” within a lytic lesion). About 1% of chondrosarcomas occurs at the skull base and commonly slightly off midline at synchondroses such as the petroclival and spheno-occipital sutures. (B) Cholesterol granulomas are thought to arise secondary to repeated episodes of hemorrhage within mucosa-lined air cells. They consist of granulation tissue and cholesterol crystals and typically are hyperintense on noncontrast T1-weighted images with areas of T2 hypointensity related to blood products. (C) In trapped secretions, the air cell septations are preserved, and there would not be erosive changes or an expansile enhancing lesion. (D) Aberrant ectoderm within petrous apex cells may result in a cholesteatoma, which does not enhance and usually is very bright on diffusion-weighted sequences due to a combination of restricted diffusion and T2 shine-through effects. (E) The vast majority of chondrosarcomas are slow-growing WHO grade I or II neoplasms that do not show significant restricted diffusion.
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A 42-year-old man with back pain underwent an MRI examination of the lumbar spine, shown in this image. What is an expected imaging finding in this patient? A. Expansion of the L5 vertebra B. Sclerosis of the contralateral pars interarticularis C. Widening of the spinal canal on a midsagittal image D. Widening of the neural foramina
C. Widening of the spinal canal on a midsagittal image ## Footnote Anterior listhesis secondary to pars defects (but not due to facet hypertrophy) often results in widening of the spinal canal on a midsagittal image. (A) Small size or hypoplasia of the L5 vertebra may predict the presence of bilateral pars interarticularis defects and should prompt a search for them. (B) Sclerosis of the contralateral pars interarticularis can occur with a chronic unilateral pars interarticularis defect. This patient likely has bilateral defects as indicated by significant listhesis of L5 over S1. (D) There may be variable degrees of neural foraminal narrowing depending on the severity of the listhesis, as can be seen on this image.
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A 40-year-old woman with a history of an intracranial aneurysm was brought to the emergency department after being found lying on the ground. An emergent CT scan showed diffuse sulcal and cisternal hyperdensity. Images from a CT angiogram and cerebral blood volume (CBV) perfusion map performed 5 days later are shown here. What complication is seen? A. Embolic infarcts following angiography B. Cerebritis C. Venous thrombosis D. Vasospasm
D. Vasospasm ## Footnote The reconstruction from the CT angiogram on the left shows marked vasospasm affecting the left greater than right middle cerebral and posterior cerebral arteries and bilateral anterior cerebral arteries. There are accompanying regions of decreased perfusion most evident in the left middle cerebral and bilateral anterior cerebral arteries, where there are acute infarctions. Clinically significant vasospasm after subarachnoid hemorrhage is seen in 30% of patients and is associated with increased mortality. (A) Embolic infarcts are a known complication of angiography, which likely was done in this patient with aneurysmal subarachnoid hemorrhage, but they tend to be small and usually are located peripherally at the gray matter–white matter junction. (B) Vasospasm following subarachnoid hemorrhage is thought to be related to the release of spasmogenic factors during lysis of subarachnoid blood clots and not due to cerebritis. (C) Venous thrombosis may result in ischemia but is not a primary complication of subarachnoid hemorrhage and would not result in the territorial arterial perfusion deficits seen in this case (primarily bilateral anterior cerebral and left middle cerebral arteries).
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A 14-year-old boy with a history of stroke presented for evaluation. 3D time-of-flight and T2-weighted sequences at the level of the circle of Willis are shown in these images. What is a characteristic of this disease? A. It most commonly presents in the elderly population. B. It may show abnormal MRI signal in engorged pial vessels. C. Dystonia and choreoathetosis are the most common clinical manifestations. D. The posterior circulation is most commonly affected.
B. It may show abnormal MRI signal in engorged pial vessels. ## Footnote The MRA (left) demonstrates extensive collateralization in the region of the proximal middle cerebral arteries due to bilateral intracranial carotid artery stenoses in a patient with (true or idiopathic) moyamoya disease. The more distal middle cerebral arteries and visualized anterior cerebral arteries are abnormally narrowed in this case with preservation of the posterior circulation. Moyamoya disease may show abnormal signal in engorged pial vessels due to collateral flow through leptomeningeal anastomoses (the “ivy sign”). Moyamoya syndrome or secondary moyamoya (different from moyamoya disease) is a nonspecific radiographic finding that can show a similar pattern of collateralization and may be seen in various entities including sickle cell disease, neurofibromatosis type 1, Down syndrome, and connective tissue disorders, among others. (A) Moyamoya disease has a bimodal age distribution with peaks between 5 and 9 years of age and 35 and 39 years of age. (C) The most common manifestations of moyamoya disease are ischemia and hemorrhage. There have been rare reports of dystonia and choreoathetosis. (D) Moyamoya disease much more commonly involves the anterior circulation, although the posterior circulation also may be affected.
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A 32-year-old woman with a long-standing history of intractable epilepsy underwent a contrastenhanced MRI of the brain, shown in these images. What is a characteristic of this lesion? A. Classified as a WHO grade II tumor B. Commonly associated with focal cortical dysplasia C. Shows low signal on apparent diffusion coefficient maps D. Most demonstrate contrast enhancement E. Has a propensity for leptomeningeal spread
B. Commonly associated with focal cortical dysplasia ## Footnote Dysembryoplastic neuroepithelial tumors (DNETs) are tumors of children and young adults who usually present with a long-standing history of intractable seizures. The lesions occur most commonly in the temporal followed by the frontal lobes, and these areas account for over 90% of cases. DNETs commonly are associated with focal dysplasia in the adjacent cortex. On imaging, they characteristically show a bubbly appearance, are cortically based, are bright on T2, and usually do not show contrast enhancement. Calcification is relatively common. (A) DNETs are WHO grade I lesions. (C) DNETs do not have restricted diffusion; therefore, they should not show low signal on apparent diffusion coefficient maps. (D) Only about 20% of DNETs show contrast enhancement in a nodular, heterogeneous, or ring-like fashion. (E) DNETs are slow-growing tumors that do not have a propensity for leptomeningeal spread.
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What is routinely a non-enhancing neural structure on contrast-enhanced MRI? A. Area postrema B. Organum vasculosum C. Fornix D. Anterior pituitary E. Pineal gland
C. Fornix ## Footnote The fornix is a white matter structure that connects the hippocampus and mammillary bodies. It features a blood–brain barrier and does not normally show contrast enhancement. (A, B, D, E) The circumventricular organs are small, highly vascularized, midline structures surrounding the third and fourth ventricles. They are devoid of a blood– brain barrier, which enables contrast enhancement to be demonstrated routinely in the larger organs. Enhancement of the smaller structures is more difficult to appreciate but has been documented to variable degrees in studies done on higher field magnets
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A patient status post–resection of a right vestibular schwannoma underwent a noncontrast MRI study, shown in these images. What vessel has been injured? A. Superior cerebellar artery B. Posterior inferior cerebellar artery C. Anterior inferior cerebellar artery D. Superior cerebellar vein E. Inferior cerebellar vein
C. Anterior inferior cerebellar artery ## Footnote There is increased FLAIR signal along with restricted diffusion involving the anterior aspect of the right cerebellar hemisphere and middle cerebellar peduncle compatible with acute infarction. The abnormality follows the arterial distribution of the anterior inferior cerebellar artery, which also supplies the inferolateral aspect of the pons and flocculus. (A) The superior cerebellar artery supplies the superior cerebellum, superior vermis, dentate nuclei, and part of the midbrain. (B) The cerebellar parenchyma posterior to the infarcted area is supplied by the posterior inferior cerebellar artery (PICA) and is not involved. The PICA is the major artery of the cerebellum and supplies its posteroinferior portion, the inferior cerebellar vermis, and the lateral medulla. (D, E) The superior and inferior cerebellar veins drain their respective regions of the cerebellum and transmit blood to the dural sinuses and deep venous vasculature. The infarct in this case shows an arterial distribution.
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A brain MRI shows a small lesion in the pons that is slightly hyperintense on T2-weighted images and shows “brush-like” enhancement and signal dropout on gradient echo sequences. There is no surrounding edema. This is consistent with what pathology? A. Demyelinating plaque B. Metastasis C. Cavernous malformation D. Capillary telangiectasia
D. Capillary telangiectasia ## Footnote The imaging description of the lesion and its location are characteristic of a capillary telangiectasia. Low signal on GRE sequences is thought to be related to slow flow and increased deoxyhemoglobin content. Capillary telangiectasias sometimes can have areas of gliosis and are nearly always asymptomatic and found incidentally. (A) A demyelinating plaque does not show the constellation of features described, which are characteristic of capillary telangiectasias. (B) Capillary telangiectasias should be differentiated from metastases. The latter usually have surrounding edema (except for small cortical lesions) and do not show signal loss on gradient echo (GRE) imaging unless they are hemorrhagic, melanotic, or calcified. (C) Cavernous malformations can show various signal intensities depending on the stage of their blood products. They typically are described as having a “popcorn” or “berry” appearance with a surrounding rim of hemosiderin.
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An axial FLAIR image is shown here. What diagnosis is represented? A. Rhombencephalosynapsis B. Dandy-Walker malformation C. Blake pouch cyst D. Mega cisterna magna E. Joubert syndrome
E. Joubert syndrome ## Footnote Joubert syndrome is characterized by vermian hypoplasia or aplasia and a lack of decussation of the superior cerebellar peduncles. Thickening and a more horizontal configuration of the superior cerebellar peduncles leads to a “molar tooth” appearance. Diffusion tensor imaging studies show a lack of the expected “red dot” of pyramidal decussation. Most cases are autosomal recessive. (A) Rhombencephalosynapsis is characterized by an absent vermis and midline continuation of the dentate nuclei, cerebellar hemispheres, and superior peduncles. (B) A Dandy-Walker malformation can result in cystic enlargement of the posterior fossa in communication with the fourth ventricle. It does not lead to a “molar tooth” deformity. (C) A Blake pouch cyst develops due to the persistence of the embryonic Blake pouch. It can exert mass effect on the posterior fossa structures. (D) A mega cisterna magna is an incidental finding that presents as an increased subarachnoid retrocerebellar space in the lower posterior fossa. It may be asymmetric and mistaken for an arachnoid cyst.
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A 9-year-old girl with a long-standing history of seizures and mental retardation presented to the emergency room with nausea, vomiting, and papilledema. Physical examination demonstrated a rash in the malar region and thick, nodular plaques with a leathery texture on the lower back. T2-weighted and contrast-enhanced T1-weighted MRI of the brain are shown in these images. What is a characteristic of the lesion depicted on the MRI scan? A. Histologically consists of balloon cells with prominent nucleoli B. Categorized as a WHO grade II tumor C. Usually develops after the fourth decade of life D. Fifty percent are associated with malignant transformation E. Typical bubbly appearance and attachment to the septum pellucidum
A. Histologically consists of balloon cells with prominent nucleoli ## Footnote The patient’s history and clinical examination are compatible with tuberous sclerosis. The facial rash represents multiple angiofibromas, which tend to occur in the malar region. The nodular plaques on the lower back are Shagreen patches, which are considered highly specific for this entity. MRI shows a mixed cystic and solid mass centered in the left foramen of Monro (location is typical) compatible with a subependymal giant cell astrocytoma (SEGA) in this clinical context. There is resultant obstructive hydrocephalus, which is why the patient presented with signs of increased intracranial pressure. Other MRI findings of tuberous sclerosis include cortical tubers, subependymal nodules, and various white matter lesions. Histologically, SEGAs consist of balloon cells with prominent nucleoli, although spindle cells may be encountered and predominate in some tumors. Pathologically, they are indistinguishable from subependymal nodules, and on imaging, the only reliable differentiating feature is an increase in tumor size over serial studies (both subependymal nodules and SEGAs can enhance). (B) SEGAs are categorized as WHO grade I lesions. (C) SEGAs become symptomatic between 10 and 30 years of age but have been reported in patients as young as 1½ years of age. It is unusually rare for a SEGA to develop after the age of 20, and, in fact, patients without this tumor by age 25 do not need continued surveillance, as per the International Tuberous Sclerosis Complex Consensus recommendations. In contrast, SEGAs diagnosed early may become symptomatic later, and lifetime monitoring may be required for such lesions. (D) Spontaneous malignant transformation of SEGAs has been described but is unusually rare. (E) A bubbly appearance on MRI and attachment to the septum pellucidum is a description that would fit a central neurocytoma.
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An axial noncontrast CT and a sagittal contrastenhanced T1-weighted MRI of the head are shown in these images. The lesion depicted likely represents a(n): A. Epidermoid B. Craniopharyngioma C. Germinoma D. Thrombosed aneurysm E. Pituitary adenoma
B. Craniopharyngioma ## Footnote A heterogeneously enhancing suprasellar mass with cystic components and calcifications in a child (note that the spheno-occipital synchondrosis has not yet fused) is a craniopharyngioma until proven otherwise. These tumors most commonly occur in children between 5 and 14 years of age (adamantinomatous type), with a second peak in adults between the ages of 50 and 75 years (papillary type). They arise from remnants of the craniopharyngeal duct and are histologically benign but locally aggressive. These tumors are almost always sellar/suprasellar, although they rarely may present as purely intrasellar or even intrasphenoid, within the third ventricle, or in the optic apparatus without a sellar component. They have solid, enhancing components and show calcifications on CT in 90% of cases. (A) Epidermoid tumors are rare in the pediatric population. Except for FLAIR and diffusion-weighted sequences, they are homogeneous, usually have a cystic appearance, and should not show enhancing solid components. (C) The suprasellar region is the second most common location for germinomas, which also tend to present in the pediatric population. Calcification is rare. (D) Aneurysms, in general, are rare in children. Aside from vascular enhancement of the lumen, they do not show solid enhancing components. They may show a calcified rim corresponding to the aneurysm wall, but they do not demonstrate the coarse, scattered calcifications seen in this case. (E) Pituitary adenomas are rare before puberty. They can be heterogeneous in the presence of cystic or hemorrhagic changes and may resemble craniopharyngiomas; however, calcification is rare in adenomas.
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What is a radiological finding in syntelencephaly? A. Absent body of the corpus callosum B. Non-separation of the frontal and occipital poles C. Absent sylvian fissure D. Absent interhemispheric fissure
A. Absent body of the corpus callosum ## Footnote Syntelencephaly is also known as the middle interhemispheric variant of the holoprosencephaly spectrum. In this entity, there is nonseparation of the midportion of the cerebral hemispheres (posterior frontal and anterior parietal lobes) and absence or hypoplasia of the body of the corpus callosum. (B) The frontal and occipital poles characteristically are separated in syntelencephaly. (C) The sylvian fissure is present in syntelencephaly but has an abnormally vertical orientation and crosses the midline in the majority of patients. (D) An interhemispheric fissure is present in syntelencephaly, but is interrupted or intercepted by the sylvian fissure crossing the midline.
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Contrast-enhanced T1 and diffusion-weighted (b = 1,000) imaging with a corresponding apparent diffusion coefficient map are shown in these images. What is a characteristic of the lesion shown? A. Ependymal rosettes may be seen. B. It is a low-grade, capillary-rich neoplasm. C. It is formed by sheets of small round blue cells. D. Rosenthal fibers may be present
C. It is formed by sheets of small round blue cells. ## Footnote These images show characteristic features of a medulloblastoma as an enhancing mass in the region of the cerebellar vermis projecting into the fourth ventricle. The lesion demonstrates restricted diffusion, as evidenced by increased signal on diffusion-weighted imaging (center) and corresponding low signal on the apparent diffusion coefficient (ADC) map (right). Of the most common posterior fossa tumors, medulloblastomas have the lowest ADC values. They are formed by sheets of small round blue cells with minimal cytoplasm, hyperchromatic nuclei, and are similar to pineoblastomas and retinoblastomas. (A) Ependymal rosettes are characteristic of ependymomas. These are “plastic” tumors that may extrude through the fourth ventricular outflow tracts in a “toothpaste” configuration. They usually show less restricted diffusion than medulloblastomas. (B) Hemangioblastomas are low-grade, capillary-rich neoplasms that can occur sporadically or in the setting of von Hippel– Lindau syndrome. They are very vascular, enhance avidly, and may show vascular flow voids. Two thirds of them may present as a cyst with an enhancing nodule (typically abutting the pial surface), and the rest are entirely solid. (D) Rosenthal fibers are characteristic of juvenile pilocytic astrocytomas. They also may be present in reactive glial tissue surrounding vascular malformations and slow-growing tumors. Rosenthal fibers have been described in pleomorphic xanthoastrocytomas and Alexander disease. The solid enhancing component of pilocytic astrocytomas usually does not demonstrate much restricted diffusion.
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What is a characteristic of neurocysticercosis? A. Lesions commonly occur at gray matter–white matter junctions B. It is acquired by ingesting undercooked pork. C. Contrast enhancement is the hallmark of the vesicular stage. D. It has an increased incidence in AIDS patients. E. Spinal cord involvement is seen in 20% of cases.
A. Lesions commonly occur at gray matter–white matter junctions ## Footnote Lesions in neurocysticercosis commonly occur at gray matter–white matter junctions due to hematogenous spread. In the racemose form, there is proliferation of lobulated cysts without a scolex, which may spread throughout the subarachnoid space and ventriculoependymal surfaces. (B) Neurocysticercosis is acquired by ingesting Taenia solium eggs shed in the feces of carriers infected with the adult tapeworm. Ingestion of undercooked pork does not cause cysticercosis but may result in taeniasis with proliferation of the adult tapeworm in the small intestine. (C) Contrast enhancement is not seen in the vesicular stage, as the organism’s membrane still is intact. There also is no surrounding edema, and patients usually are asymptomatic. Once the cyst degenerates and dies, it incites an inflammatory reaction, edema, and contrast enhancement (colloidal vesicular stage) followed by involution in the granular nodular stage, where there may be a nodular or ring enhancing lesion with a thick capsule. In the final stage (nodular calcified), the lesions calcify, and there usually is no contrast enhancement. (D) Neurocysticercosis is the most common parasitic infection of the central nervous system in immunocompetent patients. Its incidence is not increased in AIDS. (E) Spinal cord involvement is rare and occurs in about 1% of cases.
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A 23-year-old otherwise healthy man presents with first-onset seizures. What is a characteristic of the lesion depicted in the MRI study shown here? A. Can result in vasospasm after rupture B. Does not contain dermal appendages C. Demonstrates increased alanine on MR spectroscopy at short TE D. Chemical meningitis is a frequent complication. E. May degenerate into a high-grade glial tumor
A. Can result in vasospasm after rupture ## Footnote T1-weighted images without intravenous contrast (note that the choroid plexus does not enhance) demonstrate a lesion in the left frontal lobe, which is intrinsically bright due to fat and compatible with a dermoid cyst. A fat–fluid level is seen (left image), which is characteristic. There also are scattered bright subarachnoid fat droplets in the sulci as well as intraventricular extension with fat in the frontal horns. Dermoid cysts derive from the intracranial inclusion of cutaneous ectoderm during closure of the neural tube and may develop after traumatic/iatrogenic implantation. In contrast to epidermoid cysts, they contain dermal appendages (sebaceous and sweat glands and hair follicles). Rupture is a rare event, and may result in chemical meningitis, seizures, vasospasm, and ischemia. Fistulous tracts may lead to recurrent bouts of bacterial meningitis. (B) Dermoid cysts contain dermal appendages (absent in epidermoid cysts). (C) Dermoid cysts may show a lipid peak from 0.9 to 1.3 ppm. Meningiomas (not dermoid cysts) may show increased alanine on MR spectroscopy at short TE values. (D) Chemical meningitis may occur after rupture of a dermoid cyst, which is in itself a rare event. (E) Rarely, dermoid cysts may degenerate into squamous cell carcinomas but not into highgrade glial tumors.
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The lesion depicted in the MRI shown in these images was found incidentally and has been stable over many years. What is a characteristic of this lesion? A. More common in women B. Should suppress on FLAIR sequences C. Generally demonstrate restricted diffusion D. Two thirds eventually are complicated by hydrocephalus E. Lined by ependymal cells
A. More common in women ## Footnote Pineal cysts are more common in women than in men, by a ratio of 3:1. Most pineal cysts measure less than 1 cm but may be larger, with lesions greater than 4 cm reported in the literature. They typically do not enhance, but may show a thin rim of enhancement peripherally. Very rarely, nodular areas of enhancement have been reported, in which case pineal cysts cannot be distinguished from pineal region tumors on the basis of imaging. Gadolinium will diffuse slowly into pineal cysts, and, given enough time, a pineal cyst may show enhancement on delayed imaging. The majority are asymptomatic, but approximately 5% can compress the cerebral aqueduct and result in hydrocephalus. Size tends to be stable in males, but pineal cysts may grow in young females with later regression, suggesting a hormonal role in their development. (B) Pineal cysts usually do not suppress fully on FLAIR sequences. (C) Pineal cysts do not show restricted diffusion. (D) The majority of pineal cysts are asymptomatic. (E) Pineal cysts are lined by a thin layer of glial cells, fibrous tissue, and pineal parenchyma with or without calcifications.
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What is a characteristic imaging finding in spinal paragangliomas? A. “Target” sign B. Intrinsic T1 hyperintensity C. Flow voids D. Intramedullary expansion
C. Flow voids ## Footnote As with paragangliomas occurring in the neck, lesions are highly vascular, enhance avidly, and may be associated with hemorrhage. Flow voids can be seen in and around the lesion. (A) The “target” sign has been described on T2 images in neurofibromas due to a dark fibrocollagenous core. It may be seen less commonly in schwannomas probably due to the relative distribution of Antoni A and Antoni B tissues. (B) Intrinsic T1 hyperintensity sometimes can be seen in myxopapillary ependymomas, which is the other major differential diagnosis in the lumbar spine. (D) Paragangliomas are extramedullary and usually occur in the region of the filum terminale and cauda equina; therefore, they do not expand the cord, although on occasion, there may be an associated intramedullary cyst.
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A 9-month-old girl with a prior finding of ventriculomegaly on a prenatal ultrasound study underwent half Fourier acquisition single shot turbo spin echo (HASTE) T2-weighted sequences of the brain. What is a characteristic of the entity shown in this image? A. The presence of a skin-covered myelomeningocele is a requisite for its development. B. It is not clinically significant unless peg-like tonsils descend greater than 5 mm below the foramen magnum. C. Gray matter heterotopia is present in 10 to 30% of cases. D. It may be associated with a monoventricle.
C. Gray matter heterotopia is present in 10 to 30% of cases. ## Footnote The image accompanying the question shows the typical imaging features of a Chiari type 2 malformation, with descent of the brainstem through the foramen magnum, a small posterior fossa, beaking of the tectum, a flattened and elongated fourth ventricle, and a thinned/dysplastic corpus callosum. Gray matter heterotopia is seen in 10 to 30% of cases, predominantly in a periventricular distribution. (A) Virtually 100% of Chiari type 2 malformations are associated with “open” spinal dysraphism (not “closed” as with a skin-covered defect). The presence of a skin-covered myelomeningocele essentially excludes the development of a Chiari type 2 malformation, and this is the reason why some myelomeningoceles are corrected in utero. (B) This option refers to a Chiari type 1 malformation, which presents with inferior herniation of peg-like cerebellar tonsils and is usually not clinically significant unless the tonsils are displaced more than 5 mm below the foramen magnum. (D) A “monoventricle” may be seen in holoprosencephaly depending on its severity. This is not a feature of a Chiari type 2 malformation.
95
Axial T2 images of the cervical spine are shown here. What is the likely diagnosis for this pathology? A. Paraganglioma B. Ependymoma C. Meningioma D. Peripheral nerve sheath tumor
D. Peripheral nerve sheath tumor ## Footnote The pathology shown in the images accompanying the question is an extramedullary neoplasm that is partially intradural and partially extradural. It extends to the paraspinal soft tissues through the left neural foramen, which is expanded and remodeled, indicating that this is a slow-growing process. Findings are most consistent with a nerve sheath tumor. The presence of a T2 dark center (i.e., the “target sign” due to a fibrocollagenous core) in the lower image suggests a neurofibroma, although schwannomas sometimes can show a similar appearance, depending on the relative distributions of Antoni A and Antoni B tissues. (A) Paragangliomas are rare in the spine. They tend to occur in the conus medullaris and filum terminale. (B) Ependymomas usually are parenchymal except for the myxopapillary type, which occurs exclusively in the filum terminale and sometimes involves the conus medullaris. (C) Meningiomas in the spine are much more common in females and more frequently occur in the thoracic spine. They are dural-based masses, but on occasion may extrude through a neural foramen.
96
A patient with an intracerebral hemorrhage is noted to have a positive “spot sign” on a CT angiogram. This indicates a(n): A. Underlying neoplasm B. Underlying arteriovenous malformation C. Increased risk of hemorrhage expansion D. Hypertensive hemorrhage E. Underlying arteriovenous fistula
C. Increased risk of hemorrhage expansion ## Footnote The “spot sign” indicates a focus of active extravasation and predicts the expansion of a parenchymal hematoma. It is seen as a single focus or multiple foci of enhancement within the hematoma, and is present in about one third of patients within the first 6 hours after symptom onset. Other factors that have been associated with increasing hemorrhage size include large initial volumes and the use of anticoagulants. (A, B, E) The “spot sign” does not indicate the presence of a neoplasm, arteriovenous malformation, or arteriovenous fistula, although all of these may be associated with parenchymal hemorrhage. (D) The “spot sign” can be seen in, but is not exclusive to, hypertensive hemorrhage.
97
A man status post–resection of a meningioma complains of shortness of breath. The chest radiograph shows bilateral “bat-wing” pulmonary opacities, Kerley lines, peribronchial cuffing, and blunting of the costophrenic angles. What is the likely cause of his symptoms? A. Pneumonitis B. Pulmonary edema C. Aspiration D. Infection
B. Pulmonary edema ## Footnote This constellation of radiographic findings is most consistent with pulmonary edema. Blunting of the costophrenic angles reflects the presence of pleural effusions. Kerley lines represent thickening of the interlobular septa and pulmonary interstitium, and may be seen with edema, lymphatic engorgement, or carcinomatosis. Potential causes of postoperative pulmonary edema are varied and can be related to over-administration of intravenous fluids, neurogenic edema, acute respiratory distress syndrome (ARDS), hyponatremia, sepsis, and other causes. (A) Pneumonitis is a general term with various etiologies indicating alveolar inflammation, which may or may not result in pulmonary edema. (C) Aspiration pneumonia most commonly occurs in the posterior segment of the upper lobes and the superior segment of the lower lobes in postoperative patients who usually are recumbent. (D) Pneumonia usually is focal but may be extensive and bilateral if it is severe.
98
A patient with a history of seizures is found to have left-sided cerebral hemiatrophy and ipsilateral cortical/subcortical calcifications, some of which show a “tram track” configuration. What are the expected additional features of this disease entity? A. Leptomeningeal angiomatosis B. Atrophy of the ipsilateral choroid plexus C. Facial capillary malformation sparing the ophthalmic and maxillary division territories of the trigeminal nerve D. Aplasia of the ipsilateral frontal sinuses E. Thinning of the ipsilateral calvaria
A. Leptomeningeal angiomatosis ## Footnote The description of this case is consistent with Sturge-Weber syndrome, the hallmark of which is disorganized capillary vascular malformations involving the face, eye, and brain, typically on the same side. Leptomeningeal enhancement reflects the presence of a pial angiomatosis, which more commonly occurs in the parieto-occipital region and is thought to lead to cortical/subcortical calcifications due to a steal phenomenon and chronic ischemia. Patients may develop seizures, hemiplegia, and visual deficits. The pial angiomatosis is bilateral in 20% of cases where the clinical presentation is more severe. (B) In Sturge-Weber syndrome, there is engorgement of the ipsilateral choroid plexus and often recruitment of ependymal collaterals. (C) The facial capillary malformation of Sturge-Weber syndrome (“port-wine” stain) typically involves the ophthalmic division and sometimes the maxillary division of the trigeminal nerve. It virtually never involves the mandibular division in isolation. (D) The ipsilateral frontal sinuses may be enlarged due to the compensatory growth of the calvaria, sometimes resulting in the Dyke-Davidoff-Masson phenomenon (compensatory thickening of the cranial vault with frontal sinus enlargement, elevation of the petrous ridge, ipsilateral falcine displacement, and capillary malformations). (E) There is compensatory thickening of the ipsilateral calvaria in chronic cases of SturgeWeber syndrome due to the hemiatrophy
99
What finding is suggestive of cryptococcal infection? A. Concentric T2 FLAIR “target” sign B. Eccentric “target” sign C. Pseudocysts D. Enhancing nodules with low T2 signal intensity
C. Pseudocysts ## Footnote Gelatinous pseudocysts are a characteristic finding of cryptococcal meningoencephalitis and are filled with mucous exudates produced by the fungus. The pseudocysts commonly occur in the basal ganglia and medial cerebellum. Because they are not simple fluid, they do not suppress on FLAIR sequences. Patients also can have enhancing cryptococcomas and dilated perivascular spaces. (A) A concentric T2 FLAIR “target” sign is seen in one third of patients with toxoplasmosis, and represents alternating layers of necrosis, edema, and hemorrhage. (B) The eccentric “target” sign is seen on contrast-enhanced T1-weighted images, and is highly suggestive of toxoplasmosis (seen in about one third of patients with the diagnosis). (D) Low T2 signal intensity can be seen in enhancing granulomas, including cryptococcomas and tuberculomas but is not specific
100
A 52-year-old man with long-standing symptoms underwent a CT of the cervical spine, shown in this image. What is the most common clinical manifestation of the condition shown? A. Hand ischemia B. Hand and arm dysesthesia C. Muscle atrophy D. Upper extremity swelling E. Collateral vein formation
B. Hand and arm dysesthesia ## Footnote The coronal CT image shows large cervical ribs arising from the C7 vertebrae bilaterally. They may constitute a cause of thoracic outlet syndrome. By far, the most common clinical manifestations of thoracic outlet syndrome are neurogenic (about 95%), and include pain, dysesthesias, weakness, and cold intolerance in the hands, arms, or shoulders. Most commonly, neurogenic thoracic outlet syndrome involves the C8 and T1 cervical roots, which may result in symptoms along the ulnar nerve distribution. Less commonly, the upper cervical brachial plexus roots may be affected and lead to symptoms in the neck, upper chest, and back. (A) Signs and symptoms of arterial compression with or without thromboembolism, including hand ischemia, are the least common presentations of thoracic outlet syndrome, constituting approximately 1% of cases. (C) Muscle atrophy can be seen in cases of severe and prolonged compression of the brachial plexus, but this is extremely uncommon. (D) Upper extremity swelling may be a manifestation of venous compression and/or thrombosis; however, neurogenic symptoms are more common manifestations of thoracic outlet syndrome. (E) Chronic venous compression can lead to the development of collateral veins, but neurogenic symptoms are more common in thoracic outlet syndrome.
101
A man with a history of seizures undergoes an MRI of the brain, which shows numerous non-enhancing and mildly expansile cortical/subcortical lesions and subependymal nodules. There also are T2 hyperintense radial white matter lines and small parenchymal cysts. What gene is involved in this patient’s process? A. NF1 B. TSC1/TSC2 C. NF2 D. VHL E. SMARCB1
B. TSC1/TSC2 ## Footnote The constellation of findings presented is compatible with tuberous sclerosis complex (TSC). In particular, the combination of glioneuronal hamartomas (also known as cortical tubers) and subependymal nodules is sufficient to make the diagnosis as per the 2012 TSC Consensus Guidelines. White matter radial migration lines and parenchymal cysts also are characteristic. TSC can develop due to mutations in either the TSC1 or TSC2 genes, which code for hamartin and tuberin. (A) Neurofibromatosis type 1 can lead to various lesions in the central nervous system, including gliomas, sphenoid wing dysplasias, and focal areas of high signal intensity (FASI), also known as unidentified bright objects (UBOs). (C) Neurofibromatosis type 2 is characterized by the presence of multiple inherited schwannomas, meningiomas, and ependymomas (MISME). (D) The hallmark central nervous system lesions in von Hippel–Lindau disease are hemangioblastomas, which are very vascular and invariably enhance; two thirds present as typical, cystic masses with mural nodules, and the rest are entirely solid. Patients also can develop endolymphatic sac tumors as well as various extracranial lesions. (E) Mutations in the SMARCB1 and LZTR1 genes have been associated with schwannomatosis (neurofibromatosis type 3).
102
A woman is noted to have an “empty delta” sign on a contrast-enhanced CT of the head. This finding likely is secondary to: A. Cortical vein thrombosis B. Dural venous thrombosis C. Subdural blood along the posterior falx D. Deep venous thrombosis E. Subarachnoid hemorrhage
B. Dural venous thrombosis ## Footnote Dural venous thrombosis can lead to the socalled empty delta sign, due to the presence of a nonenhancing thrombus in the dural venous sinus against a background of enhancing blood in the surrounding sinus/dura. (A) Cortical vein thrombosis does not result in an empty delta sign. Depending on bolus timing, it can be seen as a filling defect on a contrast-enhanced study, hyperintensity within the vessel on FLAIR sequences, or associated blooming artifact on gradient echo–based sequences (particularly susceptibility weighted imaging). (C, E) Dense subdural or subarachnoid blood along the posterior falx and dural reflections can cause a “pseudo-delta” sign on a noncontrast CT study. (D) Deep venous thrombosis does not cause an empty delta sign.
103
The “scalpel” sign in the spine is used to describe what pathological condition? A. Epidural hematoma B. Spinal cord herniation C. Arachnoid cyst D. Dorsal arachnoid web
D. Dorsal arachnoid web ## Footnote The “scalpel” sign has been described in dorsal thoracic arachnoid webs and refers to the shape of the dorsal subarachnoid space at the level of the lesion. MRI and CT myelography show ventral displacement of the spinal cord due to the presence of an abnormal arachnoid membrane. Dorsal thoracic arachnoid webs can be associated with symptoms of long-standing cord compression. (A) Epidural hematomas can exert mass effect on the intraspinal structures. They are not associated with the “scalpel” sign. (B) Spinal cord herniation is thought to be caused by a dural defect, with resultant communication between the subarachnoid and epidural spaces. The spinal cord progressively herniates through the defect, with subsequent distortion and potential development of myelopathy. (C) An arachnoid cyst can result in variable degrees of mass effect on the spinal cord.
104
The lesion shown on this diffusion-weighted image no longer was present on a follow-up MRI performed 1 month later. What may be associated with such an abnormality? A. Demyelinating plaque B. Embolic infarct C. Antiepileptic drug usage D. Acute disseminated encephalomyelitis
C. Antiepileptic drug usage ## Footnote Antiepileptic drug usage and sudden withdrawal of antiepileptic drugs have been linked to transient splenic lesions. Various infectious, inflammatory, and autoimmune processes have been associated with a transient splenic lesion. The etiopathogenesis is uncertain. (A) A demyelinating plaque can occur in the corpus callosum but more commonly is asymmetric, and follow-up imaging may show the sequela of demyelination. (B) The corpus callosum is relatively resistant to embolic infarcts, due to the perpendicular orientation of its penetrating arteries and a rich blood supply. It would be unusual for an embolic infarct to occur at the midline. (D) Acute disseminated encephalomyelitis can affect the corpus callosum but usually is asymmetric.
105
A child presents for evaluation and undergoes a CT scan of the head. A surface-rendered 3D reconstruction is shown in this image. What gene may be altered in the patient’s disorder? A. TSC1 B. NOTCH3 C. FGFR D. SMARCB1
C. FGFR ## Footnote There is trigonocephaly resulting from premature fusion of the metopic suture, which usually closes at 6 to 12 months of age. This deformity can result in ridging along the forehead, bifrontal and bitemporal narrowing, and hypotelorism. Most cases of trigonocephaly are sporadic, and the majority of nonsyndromic cases may be related to a variety of genetic and environmental factors. Trigonocephaly may be associated with many syndromes such as Jacobsen, Saethre-Chotzen, Opitz C, and Say-Meyer, among others. Most syndromic cases are related to mutations in the FGFR genes, but alterations also may be seen in chromosomes 9, 11, and 22. (A) TSC1 and TSC2 mutations are the hallmark of tuberous sclerosis complex. (B) NOTCH3 mutations can result in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. (D) Mutations in the SMARCB1 gene can lead to Coffin-Siris syndrome and an increased risk of developing rhabdoid tumors such as ATRT.
106
A woman undergoes a myelogram of the lumbar spine, which shows an “empty sac” sign. This appearance is described in what entity? A. Arachnoid cyst B. Arachnoiditis C. Intradural tumor D. Epidural collection E. Subdural collection
B. Arachnoiditis ## Footnote An “empty sac” sign has been described in arachnoiditis due to peripheral displacement of nerve roots that are adherent to the sac. Nerve roots also can be clumped, and there rarely may be soft tissue masses in patients with fibrosing or ossifying arachnoiditis. Although most cases are postsurgical, arachnoiditis also may be seen after infection, trauma, subarachnoid hemorrhage, and intrathecal steroids. (A) An arachnoid cyst appears as a well-circumscribed filling defect within the thecal sac and can result in displacement of the spinal contents. If there is communication with the subarachnoid space, an arachnoid cyst eventually will fill with contrast and may become invisible on delayed imaging; 80% of spinal arachnoid cysts are thoracic, and only 5% are lumbar. (C) An intradural tumor can displace the spinal nerve roots but does not produce an “empty sac” sign. (D, E) Epidural and subdural collections can result in variable degrees of mass effect on the thecal sac and its contents.
107
An MRI on a patient with a left preauricular squamous cell carcinoma invading the parotid gland shows new tumor infiltration of the mandibular branch of the left trigeminal nerve and the Meckel cave. Along what nerve is the likely route of the tumoral spread? A. Maxillary nerve B. Greater superficial petrosal nerve C. Vidian nerve D. Auriculotemporal nerve
D. Auriculotemporal nerve ## Footnote The auriculotemporal nerve arises from the posterior division of the mandibular branch of the trigeminal nerve. It anastomoses with the temporofacial division of the facial nerve and is a common route of perineural spread, particularly from tumors in the temporal scalp, parotid gland, and external auditory canal. (A) The maxillary nerve is the second division of the trigeminal nerve. Perineural spread along this nerve can occur from malignancies arising in the facial region. (B, C) The greater superficial petrosal nerve is a branch of the facial nerve that arises from the geniculate ganglion. The Vidian nerve is formed by the confluence of the greater superficial petrosal nerve, deep petrosal nerve, and ascending sphenoidal branch from the otic ganglion. These are potential routes of spread in various tumors from the nasopharynx, paranasal sinuses, and orbits.
108
A 65-year-old man presenting with a relatively rapid progression of left limb ataxia and intention tremors underwent an MRI examination. Axial postcontrast T1 and diffusion-weighted (b = 1,000) images and corresponding apparent diffusion coefficient map are shown here. What is the likely diagnosis? A. Metastasis B. Glioblastoma C. Tumefactive demyelination D. Abscess E. Toxoplasmosis
A. Metastasis ## Footnote The images accompanying the question demonstrate an intra-axial mass in the left cerebellum with peripheral enhancement (left) and restricted diffusion of the enhancing component as evidenced by high signal on the diffusion-weighted image (center) and dark signal on the apparent diffusion coefficient map (ADC, right), which also demonstrates increased surrounding signal due to edema. Metastases constitute the most common cerebellar tumors in adults. (B) Primary cerebellar glioblastomas are rare and constitute less than 1% of all such tumors. Solid components may show restricted diffusion. (C) Tumefactive demyelination may present as an enhancing mass, typically with an incomplete ring of enhancement that may show variable degrees of restricted diffusion. (D) Abscesses show restricted diffusion in the central necrotic component, not in the enhancing peripheral rim. (E) Cerebral toxoplasmosis is an AIDS-defining condition, and most cases are seen in this context. Toxoplasma lesions tend to be small (2 to 3 cm) and commonly occur in the gray matter–white matter junction of the supratentorial brain and deep gray nuclei. They may show enhancement with an eccentric nodule (the “eccentric target” sign) or alternating rings of T2/FLAIR hypo- and hyperintensity related to areas of necrosis, edema, and hemorrhage.
109
The lesion found on the contrast-enhanced MRI shown here demonstrates a 1p36 deletion on fluorescence in situ hybridization. What is a characteristic of this lesion? A. Originates from arachnoid meningothelial cells B. Most common in the pediatric population C. Associated with mutations in or inactivation of hamartin D. Arises from the ependymal lining of the ventricular system E. Usually stains positive for glial fibrillary acidic protein
A. Originates from arachnoid meningothelial cells ## Footnote 1p36 deletions have been found in a variety of human cancers. In the central nervous system, these cancers include meningiomas, oligodendrogliomas, and neuroblastomas. Of these, an avidly enhancing intraventricular mass would be most consistent with a meningioma, which originates from arachnoid meningothelial cells. In meningiomas, 1p deletions are the second most common genetic abnormality after deletions on chromosome 22, and they have been associated with an increased risk of tumor recurrence and progression. (B) The incidence of meningiomas increases with age. They are very rare in the pediatric population except when they are associated with neurofibromatosis type 2, in which case they more frequently develop at an earlier age or in patients with a history of radiation therapy, although the latency in such cases may be long. (C) Hamartin is a ubiquitous protein encoded by the TSC1 gene in the tuberous sclerosis complex, where it is associated with the development of hamartomas in various tissues. It is not related to the formation of meningiomas. (D) Ependymomas, not meningiomas, arise from the ependymal lining of the ventricular system. (E) Except for a few isolated reports of papillary and rhabdoid meningiomas, these tumors do not show glial fibrillary acidic protein staining.
110
A frontal view digital subtraction angiogram following a right carotid artery injection is shown in this image. What is the likely etiology of the lesion demonstrated? A. Atherosclerosis B. Immune vasculitis C. Congenital D. Endocarditis
D. Endocarditis ## Footnote Mycotic pseudoaneurysms form after infectious disruption of all three layers of the arterial wall and formation of a vascular outpouching. These lesions characteristically arise from distal branches of the middle cerebral artery along the surface of the brain and can develop as a complication of endocarditis and septic emboli, as was the case in this patient. (A) The pathogenesis of intracranial aneurysms is complex and multifactorial. Atherosclerosis may play a role in the formation of at least some fusiform aneurysms. The lesion in this case is very peripheral, almost along the inner table of the skull (note the faint subtraction artifact related to the calvaria), a location that is more often seen in mycotic pseudoaneurysms. (B) The imaging presentation of vasculitis is variable, and in many cases the angiogram may be normal and, therefore, does not rule out the diagnosis. The classic finding in vasculitis is regions of segmental stenosis and dilatation resulting in a “string of beads” appearance. (C) Mycotic pseudoaneurysms are infectious in nature.
111
A man with altered mental status has necrosis of the retinae and optic disks. An MRI of the brain shows necrosis of the lateral putamina and white matter edema bilaterally. What is the patient’s most likely diagnosis? A. Creutzfeldt-Jakob disease B. Methanol intoxication C. Carbon monoxide intoxication D. Wernicke encephalopathy
B. Methanol intoxication ## Footnote The most characteristic imaging finding of methanol intoxication is bilateral putaminal necrosis with variable degrees of hemorrhage, and this may be accompanied by white matter edema or necrosis in severe cases. Findings are thought to be caused by the direct toxic effects of methanol metabolites and metabolic acidosis. Necrosis of the retinae and optic disks/nerves may lead to blindness. (A) The most common findings in sporadic Creutzfeldt-Jakob disease are cortical and basal ganglia signal abnormalities involving the corpus striatum. The variant form more commonly shows involvement of the pulvinar or dorsomedial thalami (“hockey-stick” sign). (C) Carbon monoxide intoxication typically affects the globus pallidus and also may involve the white matter. (D) Wernicke encephalopathy preferentially affects the mammillary bodies, medial thalami, tectal plate, and periaqueductal gray. Contrast enhancement of the thalamus and mammillary bodies has been associated with alcohol abuse.
112
A 43-year-old man involved in a motor vehicle collision underwent an emergent CT scan of the head, shown in this image. What is a characteristic of this lesion? A. Often respects cranial sutures B. Does not cross the midline C. Mixed density contents predict stability D. Most commonly occurs secondary to venous injury E. Develops between the inner and outer layers of the dura
A. Often respects cranial sutures ## Footnote The CT image shows a hyperdense, acute epidural hematoma with mass effect on the frontal lobe and mild midline shift. Classically, epidural hematomas are limited by tight dural attachments at the cranial sutures, which results in a lentiform or biconcave shape. They usually do not cross sutures unless there is a fracture or sutural diastasis. (B) Supratentorial subdural (not epidural) hematomas do not cross the midline because they are limited by the reflection of the inner layers of the dura as they form the falx cerebri. Epidural hematomas may cross the midline if there are no intervening sutures or if there is a sutural fracture or diastasis. This is seen, for instance, with vertex epidural hematomas, which usually are venous and associated with a fracture crossing the superior sagittal sinus and, therefore, can be seen across the sagittal suture. (C) Mixed density contents with areas of low attenuation within the dense hematoma (i.e., the “swirl sign”) indicate active extravasation and are an indication for emergent surgical evacuation. (D) 90 to 95% of epidural hematomas are due to an arterial injury. Epidural hematomas due to a venous injury are less common and usually are associated with fractures crossing the dural venous sinuses. (E) Epidural hematomas develop between the outer (periosteal) layer of the dura and the inner table of the skull.
113
What is a characteristic of the midbrain lesion shown in these images? A. Focal radiotherapy is the initial treatment of choice. B. The majority are low-grade lesions C. It is the most common cause of congenital hydrocephalus. D. It may be related to mutations in the L1CAM gene.
B. The majority are low-grade lesions ## Footnote The majority of tectal gliomas are low-grade lesions, but high-grade histologies also may be seen. (A) The vast majority of tectal gliomas are lowgrade, insidious lesions that can be observed for relatively long periods of time without intervention. Shunting with an endoscopic third ventriculostomy or ventriculoperitoneal drainage generally is an accepted initial treatment. Tumors that persistently are symptomatic may require further treatment, such as radiotherapy and/or chemotherapy. (C) Aqueductal stenosis is the most common cause of congenital hydrocephalus and may be secondary to congenital stenosis of the cerebral aqueduct or a sequela of intrauterine infection. (D) Five to seven percent of patients with aqueductal stenosis have a congenital form (X-linked hydrocephalus) seen in males and determined by mutations in the L1CAM gene.
114
Axial FLAIR images of the brain of a 43-year-old woman are shown here. What ancillary laboratory finding may be present? A. Serum aquaporin-4 antibodies B. Serum cryptococcal antigen C. Cerebrospinal fluid anti–Borrelia burgdorferi antibodies D. Cerebrospinal fluid IgG and IgM oligoclonal bands
D. Cerebrospinal fluid IgG and IgM oligoclonal bands ## Footnote The axial FLAIR images accompanying the question show periventricular white matter lesions in a radial orientation, and two juxtacortical (abutting the cortex) lesions on the left side, characteristic of multiple sclerosis. The presence of both periventricular and juxtacortical lesions satisfies the 2010 modified MacDonald criteria for dissemination in space. The concurrent presence of an enhancing lesion (right image) and multiple nonenhancing lesions satisfies the criteria for dissemination in time. Oligoclonal bands are found in the cerebrospinal fluid in 95% of patients with clinically definite multiple sclerosis. (A) Serum aquaporin-4 antibodies are highly specific (between 92% and 99%) for the diagnosis of neuromyelitis optica and are seen in about 60% of patients. Lesions in the brain are not entirely specific, but tend to favor areas of high aquaporin-4 expression. White matter lesions with cloud-like enhancement and ependymal enhancement may be seen. (B) Cryptococcal antigen can be detected in the serum and cerebrospinal fluid of patients with cryptococcal meningoencephalitis. Cryptococcomas and gelatinous pseudocysts preferentially develop in the basal ganglia and medial cerebellum, and patients can have dilated perivascular spaces. (C) Lyme disease is caused by the spirochete Borrelia burgdorferi. MRI findings in the brain include nonspecific white matter lesions, which sometimes may enhance, and leptomeningeal and cranial nerve enhancement
115
A 17-year-old boy with progressive facial swelling underwent a noncontrast CT scan, shown in this image. This imaging finding is consistent with: A. Blastic metastasis B. Paget disease C. Fibrous dysplasia D. Plasmacytoma
C. Fibrous dysplasia ## Footnote The CT image demonstrates osseous expansion and remodeling of the right maxilla, adjacent zygoma, and pterygoid process with a ground-glass appearance that is most consistent with fibrous dysplasia. This is a benign condition that develops as a result of abnormal osteoblastic differentiation and leads to replacement of normal marrow with immature osseous and fibrous elements. Fibrous dysplasia is a disease of children, adolescents, and young adults. It can be monostotic (80%) or polyostotic. In the head, the most common sites of involvement are the frontal, sphenoid, and ethmoid bones along with the maxilla. Although the majority of cases are sporadic, fibrous dysplasia can be seen as part of McCune-Albright and Mazabraud syndromes. On CT, the appearance is often characteristic with areas of ground-glass texture admixed with sclerotic and sometimes cystic changes. Diagnosis on MRI may be challenging, as the appearance is more variable. (A) Blastic (sclerotic) osseous metastases are seen with many primary malignancies including breast and prostate cancer and neuroendocrine tumors. They do not result in the expansile or ground-glass appearance seen in this case. (B) Paget disease essentially can occur in any bone and also can result in osseous expansion; however, it is a disease of middle-aged and elderly individuals. The ground-glass appearance of this case and the location are typical for fibrous dysplasia. (D) A plasmacytoma would have a destructive, lytic appearance on CT with or without a soft tissue component. It also is a condition seen in older individuals.
116
A 60-year-old man with gait ataxia and nystagmus underwent an MRI of the brain that showed a “hot cross bun” sign. What is an additional finding in this disease entity? A. Molar tooth configuration B. Thin middle cerebellar peduncles C. “Hummingbird” sign D. Nonvisualization of nigrosome-1
B. Thin middle cerebellar peduncles ## Footnote The “hot cross bun” sign is produced by degeneration of transverse pontine fibers and is highly specific for multiple system atrophy (MSA), although it only is seen in about half of the patients with this condition. The middle cerebellar peduncles are significantly thinned in MSA patients with predominant cerebellar ataxia, compared with patients with Parkinson disease and control individuals. (A) A molar tooth configuration is characteristic of Joubert syndrome, in which there is a lack of decussation of the superior cerebellar peduncles, which have a more horizontal trajectory. (C) The “hummingbird” sign is produced by midbrain atrophy with preserved volume of the pons in patients with supranuclear palsy. (D) Nonvisualization of the normal signal hyperintensity of nigrosome-1 has been described in patients with Parkinson disease using high field MR magnets.
117
An MRI of the brain is performed, and the report describes the presence of a lesion in the cerebellar hemisphere with a “corduroy” appearance. This lesion likely represents: A. Cerebellitis B. A medulloblastoma C. A subacute posterior inferior cerebellar artery infarct D. A dysplastic cerebellar gangliocytoma
D. A dysplastic cerebellar gangliocytoma ## Footnote A “corduroy” appearance is often used in MRI reports to describe the striated pattern that is highly characteristic of dysplastic cerebellar gangliocytoma (Lhermitte-Duclos disease). This is a hamartomatous formation occurring in the cerebellum that is seen in association with Cowden syndrome and loss of PTEN gene function. Patients are at an increased risk of developing various malignancies, including thyroid, breast, and endometrial cancer. The lesion may show increased signal on T2/FLAIR sequences and hyperperfusion. It also can be associated with increased mass effect and elevated intracranial pressure, which may necessitate ventricular decompression and/or surgical resection. (A) Cerebellitis typically does not result in a “corduroy” imaging pattern. It has various etiologies, and its presentation is varied. Cerebellitis can be unilateral, bilateral, symmetric, asymmetric, or diffuse. (B) A “corduroy” pattern is not typical of medulloblastoma; however, the desmoplastic variant of medulloblastoma features a multinodular architecture that may be confused with LhermitteDuclos disease. (C) Posterior inferior cerebellar infarcts are a known cause of mass effect in the posterior fossa and can be mistaken for tumor. They may enhance in the subacute phase, where striations may be seen related to the cerebellar folia; however, these striations tend to be thinner and more uniform than those of Lhermitte-Duclos disease.
118
What imaging characteristic would favor lymphoma over toxoplasmosis in a patient with AIDS? A. Concentric T2 FLAIR “target” sign B. Eccentric “target” sign C. Increased perfusion on an MR relative cerebral blood flow map D. Decreased uptake on thallium-201 SPECT E. Lipid peak on MR spectroscopy
C. Increased perfusion on an MR relative cerebral blood flow map ## Footnote Studies have shown increased relative cerebral blood flow (rCBV) perfusion in lymphoma compared with toxoplasmosis, although lymphomas commonly are hypovascular on perfusion imaging sequences. (A) The concentric T2 FLAIR “target” sign is characteristic of toxoplasmosis, and is produced by alternating rings of hemorrhage, edema, and necrosis within the lesion. It is present in approximately one third of cases. (B) The eccentric “target” sign is seen on contrast-enhanced T1 images and is highly suggestive of toxoplasmosis, although it is present only in about one third of cases. It is produced by a leash of inflamed leaky vessels coursing along a sulcus into the lesion. (D) Lymphomas show increased uptake of thallium-201, but the sensitivity decreases with small lesions, particularly those less than 2 cm. (E) Lipid/ lactate peaks on MR spectroscopy previously have been suggested to imply toxoplasmosis; however, further studies have shown various spectral patterns in both lymphoma and toxoplasmosis without significant differences
119
A 33-year-old woman presents to the emergency department with an abrupt-onset, recurrent “thunderclap” headache. The initial CT scan of the head shows a small-volume, convex subarachnoid hemorrhage. Lateral view digital subtraction angiography is shown in this image. What is the patient’s diagnosis? A. Venous infarction B. Reversible cerebral vasoconstriction syndrome C. Aneurysmal rupture D. Acute vascular occlusion
B. Reversible cerebral vasoconstriction syndrome ## Footnote The patient’s clinical presentation and imaging findings essentially are pathognomonic for reversible cerebral vasoconstriction syndrome. The angiogram was performed following an internal carotid injection and shows segmental multifocal narrowing involving both the anterior and posterior (through a fetal posterior cerebral artery) circulations. Initial CT and cerebrospinal fluid studies commonly are normal, although small-volume subarachnoid hemorrhage is present in 20% of patients with reversible cerebral vasoconstriction syndrome. Ischemic stroke, parenchymal hemorrhage, and areas of edema may be seen. (A) Venous infarction may present with headaches, nausea and vomiting, and altered mental status. It is not associated with recurrent “thunderclap” headaches. Additionally, only the arterial phase is shown on the angiogram. (C) There is no evidence of an aneurysm on the angiogram. (D) Acute vascular occlusion is not seen on this exam.
120
A 1-year-old boy undergoes an MRI of the chest and thoracic spine, which shows a paravertebral mass resulting in scalloping of the adjacent vertebrae and ribs. The mass demonstrated avid uptake on 123I-metaiodobenzylguanidine (123I-MIBG) scintigraphy. What is the patient’s likely diagnosis? A. Giant cell tumor B. Eosinophilic granuloma C. Neuroblastoma D. Aneurysmal bone cyst
C. Neuroblastoma ## Footnote Neuroblastomas are tumors derived from primitive sympathetic ganglion cells. The monly occur in young children with a mean age of presentation of 22 months; 40% arise from the adrenal glands, and 15% are thoracic. When paravertebral, their growth results in remodeling of the adjacent vertebrae and ribs, and they can extend into the spinal canal through the neural foramina. They show heterogeneous enhancement and may be accompanied by cystic change and necrosis. Due to their adrenergic origin, they show avid uptake of 123I-metaiodobenzylguanidine (123I-MIBG), which has shown high sensitivity and specificity. (A) Giant cell tumors rarely occur in the vertebrae. They do not accumulate 123I-MIBG. (B) Eosinophilic granuloma is the localized and most common form of Langerhans cell histiocytosis. It can occur in the spine, where it usually affects the vertebral body and may result in a vertebra plana. (D) Aneurysmal bone cysts are histologically benign but may be locally aggressive. The presence of an expansile vertebral mass with thin bone rims and fluid–blood levels is nearly pathognomonic. They do not demonstrate 123I-MIBG uptake
121
A 42-year-old patient presents to the emergency department with focal back pain not relieved by rest. He underwent an MRI examination, shown in these images. What is/are likely to be found in the patient’s history? A. Lung cancer B. Intravenous drug use C. Fall from a height D. Anemia, hypercalcemia, and renal failure E. Seronegative spondyloarthropathy
B. Intravenous drug use ## Footnote The sagittal T2 (left) and contrast-enhanced T1 (right) MR images show the typical findings of diskitis/osteomyelitis with fluid/edema in an intervertebral thoracic disk and formation of an epidural abscess that extends dorsally into the spinal canal and compresses the cord. Note the extensive end-plate destruction and bone marrow edema in the adjacent vertebrae. Diskitis/osteomyelitis is more common in males, and its incidence increases with age. Risk factors include bacteremia (nosocomial or secondary to intravenous drug use), spinal procedures, direct inoculation from trauma, and various causes of immunosuppression including diabetes. (A) Metastatic disease usually spares the intervertebral disks and would not result in a fluid collection. Additionally, the bone marrow abnormality in this case is isolated to the vertebrae contiguous with the infected disk. (C) Fall from a height may result in a fracture, which would not explain the disk-centered inflammatory findings of this case. (D) Anemia, hypercalcemia, and renal failure are findings that would be expected with multiple myeloma, which is characterized by multiple lytic lesions that may have a permeative pattern on CT or radiography. Multiple myeloma can be seen as normal on MRI or may present as multiple hyperintense foci or with a variegated, micronodular pattern. (E) A seronegative (rheumatoid factor negative) spondyloarthropathy may present as inflammatory arthritis involving the spine and sacroiliac joints, with corner erosions in the vertebrae and ankylosis
122
A 61-year-old man presents to the emergency department with 1 day of fever, seizures, and a decreased level of consciousness. FLAIR and diffusion-weighted images from an emergent MRI scan are shown here. What is a characteristic of this entity? A. Most commonly caused by herpes simplex virus type 2 B. Typically involves the basal ganglia C. Associated with hemorrhagic necrosis D. Mediated by paraneoplastic antineuronal (antiHu) nuclear antibodies E. Characterized by diffuse neoplastic glial cell infiltration
C. Associated with hemorrhagic necrosis ## Footnote Hemorrhagic necrosis is the pathological hallmark of HSV-1 encephalitis affecting primarily the limbic system and temporal lobes. The classic lesion distribution includes the mesial temporal lobes, insular cortices, and inferior frontal lobes. The abnormalities usually are bilateral but asymmetric, and MRI diffusion-weighted imaging and FLAIR sequences are the most sensitive to define their extension. Contrast enhancement is rare in the early stages of disease but may be present later along the gyri or leptomeninges. Prognosis is poor, with a high incidence of neurologic sequelae. Mortality is related directly to the time of initiation of acyclovir after disease onset. (A) Herpes simplex virus (HSV) encephalitis beyond the neonatal period is caused by HSV-1 in the majority of cases. Neonates can be infected with either HSV-1 or HSV-2 and usually present with a more diffuse type of encephalitis. (B) HSV-1 encephalitis typically spares the basal ganglia, but may cause middle cerebral artery strokes that could otherwise have a similar appearance to the image shown. (D) The majority of patients with paraneoplastic encephalomyelitis have antineuronal (anti-Hu) nuclear antibodies. The distribution of imaging abnormalities in limbic encephalitis may mimic that of HSV-1 encephalitis, but the clinical picture differs, with a more subacute progression of cognitive and behavioral changes and sometimes seizures in the former. (E) Diffuse infiltration of two or more lobes with neoplastic glial cells is the definition of gliomatosis cerebri. This potentially could mimic some of the signal abnormalities seen in HSV encephalitis but would not explain the acute presentation of symptoms in this patient.
123
A non-enhancing, cystic-appearing extra-axial lesion is seen on an MRI of the brain. What is the most important sequence that likely will aid in the characterization of this lesion? A. FLAIR B. Susceptibility weighted C. Gradient recalled echo D. T2 weighted E. Dynamic susceptibility contrast perfusion
A. FLAIR ## Footnote The two most relevant differential considerations for a nonenhancing, extra-axial, cystic mass are an arachnoid cyst and an epidermoid cyst. Arachnoid cysts follow cerebrospinal fluid signal intensity on all sequences and fully suppress on fluid-attenuated inversion recovery (FLAIR) sequences. Epidermoid cysts show a “dirty” appearance on FLAIR and very high signal intensity on diffusion-weighted sequences. (B) Susceptibilityweighted imaging (SWI) is a gradient echo MRI sequence that maximizes tissue differences by virtue of their local magnetic fields. SWI is highly sensitive to the presence of ferritin, calcium, deoxyhemoglobin, and hemosiderin, but does not play a role in characterizing arachnoid cysts. (C) Gradient recalled echo sequences generate images that are particularly susceptible to magnetic field inhomogeneities. Dynamic susceptibility contrast MRI and functional MRI are different techniques based on GRE sequences. (D) T2-weighted images would not be helpful, as both epidermoid tumors and arachnoid cysts will show high signal. (E) Dynamic susceptibility contrast perfusion would show only a nonperfusing, space-occupying lesion and would not aid in differentiation.
124
Occlusion of the vessel shown in this image (arrow) may result in infarction of what territories? A. Superior cerebellum, superior vermis, dentate nuclei, and part of the midbrain B. Posteroinferior cerebellum, inferior cerebellar vermis, and lateral medulla C. Occipital lobe, thalamus, and part of the midbrain D. Anterior aspect of the right cerebellar hemisphere and middle cerebellar peduncle
C. Occipital lobe, thalamus, and part of the midbrain ## Footnote This is a digital subtraction angiogram following an internal carotid injection. It shows a fetal origin of the posterior cerebral artery that supplies the occipital lobe, thalamus, and part of the midbrain. (A) The superior cerebellar artery supplies the superior cerebellum, superior vermis, dentate nuclei, and part of the midbrain. (B) The posterior inferior cerebellar artery supplies the posteroinferior cerebellum, inferior cerebellar vermis, and lateral medulla. (D) The anterior inferior cerebellar artery supplies the anterior aspect of the right cerebellar hemisphere, middle cerebellar peduncle, inferolateral aspect of the pons, and flocculus.
125
A 65-year-old man patient underwent an MRI of the brain, shown in these images. What is the patient’s likely diagnosis? A. Aneurysm B. Meningioma C. Choroid plexus tumor D. Subependymoma
A. Aneurysm ## Footnote This is a well-circumscribed extra-axial lesion with mixed signal intensities and profound peripheral T2 hypointensity along the expected course of the posterior inferior cerebellar artery (PICA). Findings are most concerning for an aneurysm, which probably is partially thrombosed (note the enhancement of a nonthrombosed lumen on the third image). There is a small, old infarct in the left cerebellum seen on the FLAIR image likely related to thromboembolism. PICA aneurysms are rare, and the great majority arises proximally. (B) Although most meningiomas enhance homogeneously, they can calcify and sometimes present with cystic change or, very rarely, hemorrhage, and therefore they also may show variable signal intensities on MRI. Eighty percent of intraventricular meningiomas arise from the atrium of the lateral ventricle, and only 5% are seen in the fourth ventricle. (C) Eighty percent of choroid plexus tumors are benign papillomas. They are rare in adults, where they most commonly occur in the fourth ventricle. Papillomas tend to enhance avidly and diffusely and characteristically show frondlike margins with a texture that is similar to that of the normal choroid plexus. (D) Subependymomas are slow-growing tumors that commonly are seen in adults. They most commonly occur in the fourth ventricle, particularly at the obex followed by the frontal horns of the lateral ventricles. They typically do not enhance, but enhancement may be seen in a minority of them.
126
A woman underwent an MRI of the brain, shown in these images) for evaluation of headaches. What is the likely diagnosis? A. Giant perivascular space B. Dysembryoplastic neuroepithelial tumor C. Metastasis D. Cystic glioma
A. Giant perivascular space ## Footnote This lesion is formed by a cluster of cystic spaces that follow cerebrospinal fluid signal and fully suppress on FLAIR sequences. There is a small FLAIR hyperintense focus in the intervening parenchyma, consistent with gliosis, but no evidence of mass effect or any contrast enhancement. A somewhat branching pattern is present, which may be easier to appreciate on consecutive slices. Findings are most consistent with a giant or tumefactive perivascular space. Although headache is the most common complaint, its association with the presence of a giant perivascular space is uncertain. (B) Dysembryoplastic neuroepithelial tumors can have a bubbly appearance, and most do not enhance. These lesions are centered in the cortex, and there usually is some identifiable mass effect. Note that the cortex is thinned but not primarily involved in this case. (C) Metastases almost always have some degree of contrast enhancement. A lesion of this size also should have considerable surrounding edema. (D) A cystic glioma would be associated with enhancing components or with nonenhancing infiltrative tumor, none of which are evident in this case.
127
A 9-year-old girl with a history of uncontrollable laughing spells underwent an MRI scan and was found to have the lesion depicted in this image that was isointense to the cerebral cortex on T1-weighted images (not shown). What is an additional expected diagnostic feature of this entity? A. Precocious puberty B. Moderate contrast enhancement C. Progressive growth D. Coarse calcifications
A. Precocious puberty ## Footnote A nonenhancing mass that is isointense to gray matter in this location in a patient of this age is suggestive of a hypothalamic (tuber cinereum) hamartoma. These hamartomas are composed of disorganized neural elements, can be sessile or pedunculated, and may be iso- to hyperintense on T2 images (as in this case), depending on the proportion of glial cells within them. These are benign lesions that do not grow and classically are associated with central precocious puberty and uncontrollable laughing spells (gelastic seizures). The main diagnostic consideration is a low-grade glioma. (B–D) Hypothalamic hamartomas do not enhance or grow, and calcifications are rare.
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A brain MRI of a 32-year-old man shows numerous parenchymal lesions of various sizes that have a “popcorn” or “berry” appearance and show signal loss on susceptibility-weighted sequences. There is no history of prior radiation. What is a possible germline gene mutation in this patient? A. ENG B. CCM1 C. ACVRL1 D. RASA1
B. CCM1 ## Footnote Approximately 20% of cavernomas are familial, and these are more commonly multiple. They can be associated with mutations in the CCM1 (usually in Hispanics), CCM2, or CCM3 genes. (A) Mutations in the ENG gene are associated with hereditary hemorrhagic telangiectasia type 1. (C) Mutations in the ACVRL1 gene are associated with hereditary hemorrhagic telangiectasia type 2. (D) Phenotypic manifestations of RASA1 gene mutations include capillary and arteriovenous malformations and arteriovenous fistulas.
129
A sagittal MRI of the brain is shown in this image. What is the likely diagnosis? A. Craniopharyngioma B. Rathke cleft cyst C. Lymphocytic hypophysitis D. Granular cell tumor E. Neurosarcoidosis
B. Rathke cleft cyst ## Footnote Rathke cleft cysts are true cysts lined by epithelium that develop from remnants of Rathke’s pouch between the pars intermedia and pars distalis of the pituitary gland. Because the pars intermedia is difficult to visualize on imaging, it typically appears as a homogeneous mass separating the adenohypophysis from the neurohypophysis. It almost always is homogeneous, and its signal intensity varies depending on the presence of triglycerides, cholesterol, and protein (note intrinsic T1 hyperintensity on this noncontrast scan). It sometimes can occur in the suprasellar compartment and almost never is symptomatic. (A) Craniopharyngiomas are heterogeneous masses that usually arise at the level of the infundibulum. They show areas of enhancement, and the great majority of the adamantinomatous type (seen predominantly in children) have associated calcifications. (C) Lymphocytic hypophysitis is a nonneoplastic inflammatory condition that may affect any part of the pituitary gland and infundibulum. It does not present as a discrete mass, as seen in this case. (D) Granular cell tumors arise from granular cell nests in the neurohypophysis or infundibulum. They most commonly are suprasellar and almost never are purely intrasellar. Note the normalappearing posterior pituitary bright spot along the posterior aspect of the cyst. (E) Neurosarcoidosis can involve the pituitary gland and infundibulum but would not result in a discrete, well-defined mass with intrinsic T1 hyperintensity, as in this case.
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What characteristic is more common in adult craniopharyngiomas compared with those that occur in children? A. Cystic changes B. Solid appearance C. Calcifications D. Heterogeneous contrast enhancement E. Lower apparent diffusion coefficient values
B. Solid appearance ## Footnote Craniopharyngiomas have a bimodal distribution with peaks at 5 to 14 years of age and 50 to 75 years of age. Adamantinomatous craniopharyngiomas tend to occur in children and more commonly are associated with cystic changes (filled with what is described as “motor oil” on gross exam) and calcifications. Adult craniopharyngiomas more commonly are of the papillary subtype and are more solid and devoid of cystic changes. (A) Cystic changes are more common in adamantinomatous craniopharyngiomas, which usually occur in children. (C) Calcifications are more common in adamantinomatous craniopharyngiomas. (D) Heterogeneous contrast enhancement can be present in both types of craniopharyngiomas but may be more commonly homogeneous in the papillary type due to their usually solid appearance. (E) Apparent diffusion coefficient (ADC) values do not discriminate between papillary and adamantinomatous craniopharyngiomas. They may, however, help distinguish solid papillary craniopharyngiomas from germinomas, which show restricted diffusion and therefore lower ADC values by virtue of their high cellularity.
131
A high-resolution axial CT of the left temporal bone is shown in this image. To what structure does the arrow point? A. Singular canal B. Facial nerve canal C. Vestibular aqueduct D. Semicircular canal
D. Semicircular canal ## Footnote The arrow points to the posterior limb of the posterior semicircular canal. (A) The singular canal transmits nerve fibers from the vestibule to the posterior semicircular canal. It is very small and not shown on this image. (B) The tympanic segment of the facial nerve canal can be seen more anteriorly along the medial aspect of the epitympanum. (C) The normal vestibular aqueduct is seen as a flat line posterior and medial to the posterior semicircular canal.
132
What is an imaging characteristic of progressive multifocal leukoencephalopathy? A. Symmetric signal abnormalities B. Prominent edema C. Leading edge of high diffusion-weighted imaging signal D. Heterogeneous enhancement E. Sparing of subcortical U fibers
C. Leading edge of high diffusion-weighted imaging signal ## Footnote A leading edge of high diffusion-weighted imaging signal has been described in larger and new progressive multifocal leukoencephalopathy (PML) lesions and is thought to be related to cytotoxic edema. (A) Signal abnormalities in PML are usually bilateral but asymmetric. (B) There generally is no significant edema in PML, and when it is present, it should raise concern about immune reconstitution inflammatory syndrome (IRIS), particularly when accompanied by contrast enhancement. (D) There usually is no contrast enhancement in PML. (E) ­Involvement of the U fibers is a characteristic of subcortical PML, which results in a scalloped appearance.
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The lesion shown in these images demonstrates sheets of densely packed cells, hyperchromatic nuclei, and Homer-Wright rosettes. What is a common neuroimaging feature of this lesion? A. Low apparent diffusion coefficient values B. “Engulfed” calcifications C. Low density on CT D. Dural tail
A. Low apparent diffusion coefficient values ## Footnote The lesion’s location, imaging characteristics, and pathological description are most consistent with a pineoblastoma. These lesions are primitive neuroectodermal tumors that most commonly occur in children younger than 10 years of age. Like other highly cellular tumors with a similar histology, pineoblastomas commonly have profound restricted diffusion due to very low apparent diffusion coefficient values. (B) “Engulfed” calcifications characteristically are described in germinomas. Calcifications in pineoblastomas tend to be more peripheral (“exploded”). (C) Because of their high cellularity, pineoblastomas usually show high density on CT. They may be heterogeneous due to cystic changes and necrosis. (D) A dural tail is characteristically seen in meningiomas. It should enhance more avidly than the tumor and taper away from it.
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A 28-year-old woman presents with acute-onset severe headache and diplopia. Representative MR images are shown here. What is the patient’s likely diagnosis? A. Pituitary apoplexy B. Craniopharyngioma C. Epidermoid D. Aneurysmal rupture
A. Pituitary apoplexy ## Footnote Pre- and postcontrast MR images of the pituitary fossa accompany the question. The noncontrast image (left; note the lack of enhancement of the nasal mucosa) shows bright foci expanding the pituitary gland consistent with blood products. Pituitary apoplexy is an acute syndrome that can present with severe headaches, diplopia (due to mass effect on the oculomotor nerves), visual deficits (if the optic chiasm or optic nerves are compressed), and hypopituitarism. Sudden deficiency of adrenocorticotropin/cortisol may result in lifethreatening hypotension. Hemorrhage usually occurs into a preexisting pituitary adenoma (such as in this case; note how the sella is mildly expanded) and rarely into a healthy gland. (B) Craniopharyngiomas typically are seen in children but have a bimodal age peak and also can present in young and middle-aged adults. They tend to develop around the infundibulum (rather than within the pituitary gland) and have a more insidious course compared with pituitary apoplexy. (C) Epidermoid tumors in this region usually are suprasellar. On T1-weighted sequences, they tend to have signal intensities close to that of cerebrospinal fluid and do not enhance. They may result in mass effect on adjacent structures, but their presentation would be more insidious than pituitary apoplexy. (D) Aneurysms can have unusual signal intensities due to thrombosis and also can present with acute headache if they rupture. The lesion in this case arises within the pituitary gland as can be seen by small claws of enhancing tissue around the hemorrhage.
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The lesion shown here, found in a 25-year-old woman, was hyperdense to gray matter on noncontrast CT and showed restricted diffusivity on apparent diffusion coefficient maps. A normal pituitary gland was identified on sagittal MRI (not shown). Pathology demonstrated sheets of large, polygonal primitive cells with clear, glycogen-rich cytoplasm and abundance of lymphocytes. How does this lesion respond to radiation? A. The pathology is entirely radiation insensitive and should not be treated by radiation. B. The lesion is mostly radiation insensitive, but radiation may be somewhat effective. C. The lesion is mostly radiation sensitive, and radiation typically may be effective. D. The lesion is entirely radiation sensitive and should be treated primarily by radiation.
D. The lesion is entirely radiation sensitive and should be treated primarily by radiation. ## Footnote The imaging and pathological characteristics of this mass in a young adult are most consistent with a germinoma. A normal pituitary gland is present on the sagittal images; therefore, this is not a pituitary adenoma. Germinomas usually demonstrate avid homogeneous enhancement as well as restricted diffusion on MRI apparent diffusion coefficient maps and hyperdensity on CT due to their high cellularity. Although pineal region germinomas are significantly more frequent in males (male-to-female ratio of 10:1), the gender distribution of suprasellar lesions is relatively even. Pure germinomas are exquisitely sensitive to radiation, with long-term progression-free survival rates greater than 90% for localized lesions; therefore, this constitutes the mainstay of therapy, and gross total resection is not usually recommended for pure germinomas. The role of surgery in such cases generally is limited to tissue biopsy and decompression in cases of acute visual symptoms (in suprasellar lesions) or obstructive hydrocephalus (in pineal lesions). Although most germinomas do respond to chemotherapy, chemotherapy alone is associated with high rates of relapse.
136
What presentation is consistent with the MRI shown in this image? A. Vision loss B. Hemiparesis C. Gait ataxia D. Wallenberg syndrome E. Locked-in syndrome
B. Hemiparesis ## Footnote The axial FLAIR image shows increased signal in the visualized portions of the right internal carotid artery within the carotid canal due to thrombosis, which may result in left hemiparesis if there is resultant anterior circulation ischemia. (A) Vision loss may be seen as a consequence of posterior circulation infarcts involving the visual cortex. (C) Gait ataxia may result from occlusion of the cerebellar arteries. (D) Lateral medullary syndrome (also known as Wallenberg syndrome) usually results from posterior inferior cerebellar artery territory infarcts. (E) Locked-in syndrome may be secondary to infarcts of the lower pons in the proximal basilar artery territory
137
An otherwise healthy child underwent an MRI examination under general anesthesia for evaluation of sensorineural hearing loss. The study showed mild, diffuse sulcal FLAIR nonsuppression. The patient is otherwise asymptomatic and fully alert after recovery from the anesthesia. What is the likely cause of this imaging finding? A. Leptomeningeal tumor spread B. Meningitis C. Subarachnoid blood D. High FiO2 concentration
D. High FiO2 concentration ## Footnote High FiO2 concentrations have been shown to result in sulcal FLAIR nonsuppression and is a commonly encountered phenomenon in patients undergoing general anesthesia. Keeping FiO2 concentrations below 50% decreases the incidence of this finding. Causes of FLAIR nonsuppression include leptomeningeal disease (infectious or carcinomatous meningitis), subarachnoid hemorrhage, prior gadolinium administration in patients with renal insufficiency, and susceptibility artifacts commonly from metallic dental orthodontia and ventriculoperitoneal shunt reservoirs. (A) Leptomeningeal tumor spread would be highly unlikely in an asymptomatic and otherwise healthy child. (B, C) Meningitis and subarachnoid hemorrhage are unlikely, given the patient’s clinical background.
138
What is a neuroimaging feature of uncomplicated cystic hydatid disease of the brain? A. Perilesional edema B. Well-circumscribed margins C. Restricted diffusion D. Enhancement E. Calcification
B. Well-circumscribed margins ## Footnote Hydatid cysts usually have well-circumscribed margins with a thin wall that is hypointense on T1 and T2 images. They are spherical and typically occur in the middle cerebral artery distribution.Their signal tends to follow that of cerebrospinal fluid. (A) Perilesional edema is absent in hydatid cysts unless there is superimposed infection or rupture. (C, D) Hydatid cysts do not show restricted diffusion or enhancement unless there is superimposed infection. (E) There is usually no calcification in hydatid cysts.
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A 5-year-old otherwise healthy girl presents with a several-week history of neck pain. An MRI of the cervical spine was performed, and a sagittal T2 image is shown here. What is the patient’s likely diagnosis? A. Metastasis B. Eosinophilic granuloma C. Telangiectatic osteosarcoma D. Diskitis-osteomyelitis E. Fracture
B. Eosinophilic granuloma ## Footnote Eosinophilic granuloma is the localized form of Langerhans cell histiocytosis characterized by infiltration with myeloid dendritic cells. In the spine, it most commonly affects the vertebral body and can result in a vertebra plana with variable degrees of epidural or paravertebral tissue. T2 signal tends to be normal or near normal. (A) Metastases from neuroblastoma usually are more heterogeneous and ill defined. They also may present with a soft tissue component projecting outside of the vertebra. (C) Telangiectatic osteosarcomas of the spine are rare. They are heterogeneous and frequently hemorrhagic with fluid–fluid levels. (D) Diskitisosteomyelitis is an infectious process that, in children, probably begins in the disk (which still is vascularized). It would result in increased T2 signal within the disk and variable degrees of end-plate destruction (not present in this case). (E) A fracture would not have such a homogeneous appearance with smooth margins unless it is chronic. It also would not explain the solid-appearing tissue bulging into the prevertebral region.
140
What is the structure indicated by the arrow on this lateral view digital subtraction angiogram? A. Sphenoparietal sinus B. Superior petrosal sinus C. Inferior petrosal sinus D. Inferior anastomotic vein E. Marginal sinus
C. Inferior petrosal sinus ## Footnote Shown in the image accompanying the question is the inferior petrosal sinus, which generally transmits blood from the cavernous sinus to the jugular vein or, less commonly, to the suboccipital venous plexus via the hypoglossal canal; however, there is marked anatomic variation. (A) The sphenoparietal sinus receives tributaries from the middle cerebral, middle meningeal, and anterior diploic veins, and drains into the cavernous sinus. It courses along the ridge of the lesser wing of the sphenoid bone. (B) The superior petrosal sinus runs along the superior aspect of the petrous bone and drains blood from the cavernous sinus into the transverse sinus. (D) The inferior anastomotic vein (of Labbé) drains the temporal convexity and opercular region transmitting blood from the middle cerebral vein to the transverse or sigmoid sinus. (E) The marginal sinus extends along the rim of the foramen magnum
141
What is a characteristic of intracranial lipomas? A. The curvilinear type is associated with callosal dysgenesis. B. They arise from anomalous differentiation of the meninx primitiva C. They show increased signal on STIR sequences. D. They almost never calcify. E. Approximately 20% arise at the midline.
B. They arise from anomalous differentiation of the meninx primitiva ## Footnote Intracranial lipomas are congenital lesions and not true neoplasms. They arise from anomalous differentiation of the meninx primitiva. (A) The tubulonodular variant and not the curvilinear type of intracranial lipoma is associated with callosal dysgenesis. (C) Short-tau inversion recovery (STIR) sequences nonselectively suppress fat and other tissues that have a short T1 values; therefore, a lipoma would demonstrate suppressed signal. (D) Calcification is common in pericallosal and interhemispheric lipomas, particularly in association with callosal dysgenesis. (E) Approximately 85% of intracranial lipomas arise at the midline. They are less commonly seen in the quadrigeminal plate, cerebellopontine angle, suprasellar, and sylvian cisterns.
142
What grade is the intraventricular hemorrhage demonstrated on the cranial ultrasound image shown here? A. Grade 1 B. Grade 2 C. Grade 3 D. Grade 4 E. Grade 5
D. Grade 4 ## Footnote The coronal ultrasound image accompanying the question shows intraventricular hemorrhage involving the entire right lateral ventricle and left temporal horn. There is extensive parenchymal abnormality surrounding the right lateral ventricle due to venous ischemia. Findings are consistent with grade 4 intraventricular hemorrhage. Note ventricular dilatation. (A) Grade 1 intraventricular hemorrhage is confined to the germinal matrices, which are located in the caudothalamic grooves. (B) Grade 2 intraventricular hemorrhage is defined by intraventricular hemorrhage extension with normal-sized ventricles. (C) Grade 3 intraventricular hemorrhage is defined by intraventricular hemorrhage extension accompanied by ventricular distention. (E) There is no grade 5 intraventricular hemorrhage.
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Representative MR images of the brain are shown here. What is the likely diagnosis? A. Arachnoid cyst B. Giant perivascular space C. Neuroglial cyst D. Cysticercal cyst
C. Neuroglial cyst ## Footnote The axial T2 image accompanying the question shows a well-circumscribed, cystic-appearing parenchymal lesion in the right cerebellum with an imperceptible wall. There is no contrast enhancement. Findings are most consistent with a neuroglial cyst. These are benign, epithelial-lined lesions of different sizes that can be found virtually anywhere in the neuraxis. There typically is no surrounding edema. (A) Arachnoid cysts are extra-axial. This is an intra-axial lesion, as it is nearly completely surrounded by parenchyma. (B) Even though they can occur in isolation, giant perivascular spaces usually have some structure to them and often show a clustered or branching pattern. It would be very unusual for one to present as a single, well-circumscribed cyst. Giant perivascular spaces can have areas of FLAIR hyperintensity due to gliosis around them. (D) Cysticercal cysts usually are smaller than the pictured cyst. A scolex, wall enhancement, calcification, or surrounding edema may be seen depending on the Escobar stage of the parasite. The racemose form can develop within the subarachnoid space or ventricles and appears like a cluster of cysts.
144
A coronal T2-weighted image of the brain of a pediatric patient is shown here. What may be seen in the depicted disease entity? A. Increased N-acetylaspartate on MR spectroscopy B. Increased FDG uptake interictally C. Hypertrophy of the ipsilateral fornix D. Atrophy of the ipsilateral mammillary body
D. Atrophy of the ipsilateral mammillary body ## Footnote The image accompanying the question shows atrophy and loss of the internal architecture of the right hippocampus with increased signal. Additionally, there is atrophy of the ipsilateral mammillary body compared with the left, as can be seen in severe and long-standing cases of mesial temporal sclerosis. (A) MR spectroscopy may show decreased N-acetylaspartate and mildly increased myoinositol in mesial temporal sclerosis. (B) FDGPET may by useful by showing decreased metabolism/uptake in the hippocampus in patients with mesial temporal sclerosis even in the absence of structural abnormalities on MRI. (C) Atrophy of the ipsilateral fornix can be seen in severe and longstanding cases of mesial temporal sclerosis.
145
What is a characteristic of the lesion depicted on the CT and MR images shown here? A. Requires a pial-arachnoid defect B. Majority are iatrogenic C. Lined by true epithelium D. Lined by an arachnoid membrane
A. Requires a pial-arachnoid defect ## Footnote The images accompanying the question show an intracerebral pneumatocele. The coronal CT reformat (left) shows a fracture through the right frontal sinus and air tracking intracranially with the formation of a parenchymal air cyst, which can be characterized best on the axial T2 image (right). There also is a cerebrospinal fluid level present within the cyst. An intracerebral pneumatocele requires a defect in the pia-arachnoid membrane in close proximity to a craniodural defect. Air may accumulate due a ball valve effect or possibly due to increased cerebrospinal fluid leakage, leading to slightly negative intracranial pressures. (B) About 75 to 90% of intracerebral pneumatoceles are secondary to trauma as in this case. Pneumatoceles are present in up to 25% of all cases of pneumocephalus. (C) Pneumatoceles are not true cysts, and therefore are not lined by epithelium. (D) Arachnoid cysts are lined by arachnoid cells formed by the splitting of arachnoid membranes.
146
T2-weighted MR images of the cervical spine in a patient with history of trauma are shown here. What is an additional imaging finding that may be seen? A. Contrast enhancement of the ovoid lesions B. Signal suppression of the ovoid lesions on STIR images C. Enhancement of the paraspinal musculature D. Restricted diffusion in the ovoid lesions
C. Enhancement of the paraspinal musculature ## Footnote Enhancement of the paraspinal musculature is an indirect sign of avulsion injury due to denervation. Enhancement of intradural nerve roots indicates functional avulsion even in the presence of a normal-appearing nerve. (A) These lesions are fluid-filled pseudomeningoceles and would not show contrast enhancement unless they were infected. (B) Fatty lesions would show suppression of signal on STIR images. (D) Restricted diffusion may be seen in many disease processes. In the spinal cord, it can be secondary to infection or cord ischemia. The pseudomeningoceles in this case would not show restricted diffusion.
147
What anatomic structure is indicated by the arrow in this image? A. Oculomotor nerve B. Trochlear nerve C. Trigeminal nerve D. Abducens nerve E. Glossopharyngeal nerve
C. Trigeminal nerve ## Footnote Shown in the image accompanying the question is the trigeminal nerve, which arises from the lateral aspects of the pons. It has a characteristic shape, with fibers that appear to spread out before piercing the dura and entering the Meckel cave. (A) The oculomotor nerves are relatively thick and can be identified exiting the brainstem at the level of the pontomesencephalic junction. They course between the posterior cerebral and superior cerebellar arteries on coronal images. (B) The trochlear nerve generally is not seen on CISS or FIESTA images due to its small caliber, unless thinner slices are acquired (0.4 mm). (D) The abducens nerves are thin and can be seen exiting the brainstem at the level of the pontomedullary junction. (E) The glossopharyngeal nerve is part of the cranial nerve IX–X–XI complex. It exits the upper medulla and leaves the skull through the pars nervosa of the jugular foramen.
148
A 23-year-old man sustained trauma to the right side of his neck during a motor vehicle collision. The CT angiogram is shown here. What is the patient’s diagnosis? A. Vertebral artery dissection B. Carotid artery pseudoaneurysm C. Carotid artery dissection D. Vertebral artery pseudoaneurysm E. Node of Rouvière
C. Carotid artery dissection ## Footnote The axial CT angiogram image shown here demonstrates a crescentic, eccentric soft tissue density along the lateral aspect of the right internal carotid artery (arrows) consistent with a dissection. These dissections can be traumatic, as in this case, or associated with collagen vascular disease or iatrogenic causes. They may result in ischemic or embolic strokes and can be associated with pseudoaneurysm formation, Horner syndrome, or retinal ischemia. (A) There is no visible vertebral dissection. (B) Pseudoaneurysms sometimes may complicate a carotid artery dissection and may occur within hours, months, or years after the initial injury. In a pseudoaneurysm, the intima, media, and adventitia of the arterial wall are absent. (D) The visualized vertebral arteries are normal in this case. (E) The node of Rouvière is the most superior of the lateral retropharyngeal nodes. In children, it most commonly is enlarged secondary to infection, but it raises suspicion about malignancy of the upper aerodigestive tract in older patients.
149
The lesion in the right sacrum on the noncontrast CT study shown in this image likely represents: A. Blastic metastasis B. Osteoid osteoma C. Enostosis D. Osteoblastoma
C. Enostosis ## Footnote The density of the lesion and radiating spicules that blend with the surrounding trabeculae are classic findings for an enostosis, commonly known as a bone island. These are incidental benign lesions that occur in cancellous bone. (A) Blastic metastases can be secondary to a variety of tumors. Bone islands sometimes can be mistaken for metastases when their characteristic imaging findings are not present. (B) Osteoid osteomas usually present as a lucent nidus surrounded by sclerotic bone and may have a dense, calcified center. They more commonly occur in long bones and in the spine where they preferentially involve the posterior elements. (D) Osteoblastomas are benign lesions that may be locally aggressive. They are histologically similar to osteoid osteomas but are much larger. They are predominantly lytic (unlike enostoses, which are dense), but may have matrix mineralization that can be seen on CT.
150
What skull lesion characteristically is lytic without sclerotic margins? A. Chondroblastoma B. Epidermoid C. Eosinophilic granuloma D. Osteoid osteoma
C. Eosinophilic granuloma ## Footnote Eosinophilic granulomas, plasmacytoma/multiple myeloma, and most metastases are examples of lytic lesions with sharply circumscribed margins and no surrounding sclerosis. (A) Chondroblastomas are benign, slow-growing lesions that commonly present with a sclerotic margin. (B) Calvarial epidermoids typically present as lucent lesions with a sclerotic rim due to their slow growth. (D) Osteoid osteomas consist of a radiolucent nidus surrounded by sclerotic bone.
151
A 56-year-old woman with left hemiballismus undergoes an MRI of the brain. Noncontrast T1 images show hyperintensity in the right lentiform nucleus and caudate nucleus head. What is the patient’s likely diagnosis? A. Carbon monoxide intoxication B. Hyperglycemia C. Methanol intoxication D. Liver disease
B. Hyperglycemia ## Footnote Nonketotic hyperglycemia can be associated with hemiballismus. The most consistent imaging finding is the presence of hyperintensity unilaterally involving the lentiform nucleus and caudate nucleus head, which may be accompanied by T2 hypointensity and restricted diffusion. The reason for these signal changes is not entirely certain. (A) Carbon monoxide intoxication is not associated with unilateral basal ganglia lesions. Increased T2/FLAIR signal abnormalities and restricted diffusion may be present in the globi pallidi and cerebral white matter, including the corpus callosum following this type of injury. (C) The characteristic imaging finding in methanol intoxication is bilateral hemorrhagic putaminal necrosis and variable degrees of cerebral edema. (D) Liver disease can lead to T1 hyperintense basal ganglia, but the findings usually are bilateral.
152
The “white cerebellum” sign indicates what process? A. Anoxic-ischemic brain injury B. Cerebellitis C. Cerebellar neoplasm D. Rhombencephalosynapsis
A. Anoxic-ischemic brain injury ## Footnote The “white” (or dense) cerebellum sign is secondary to a relatively increased density of the cerebellum, thalami, and brainstem due to extensive hypoattenuation of the supratentorial brain. It represents anoxic-ischemic brain injury and portends a grim prognosis. (B) Cerebellitis would result in hypoattenuation of the edematous areas, which may be focal or diffuse. (C) Cerebellar neoplasms may show increased or decreased density, depending on their histologies. Medulloblastomas, for instance, tend to be hyperdense due to their high cellularity. (D) Rhombencephalosynapsis consists of absence of the vermis with fusion of the dentate nuclei, cerebellar hemispheres, and superior peduncles
153
What anatomic variant is shown on the time-offlight MR angiography in this image? A. Persistent hypoglossal artery B. Persistent trigeminal artery C. Persistent otic artery D. Persistent stapedial artery E. Persistent pro-atlantal artery
B. Persistent trigeminal artery ## Footnote A primitive trigeminal artery is the most common of the persistent fetal carotid-vertebrobasilar anastomoses. It arises at the junction of the cavernous and petrous segments of the internal carotid artery and courses along the trigeminal nerve or over the dorsum sellae. It may be associated with hypoplasia of the basilar artery, and a possible increased incidence of intracranial aneurysms and vascular malformations has also been described. (A) A persistent hypoglossal artery is second in frequency after a persistent trigeminal artery (although still much less common). It originates from the distal cervical internal carotid artery and courses through an enlarged hypoglossal canal to terminate in the basilar artery. (C) The primitive otic artery is the earliest fetal artery to disappear in embryonic life and represents the least common of the persistent fetal carotid-vertebrobasilar anastomoses. It arises from the internal carotid artery within the carotid canal and courses through the internal acoustic meatus to join the basilar artery. (D) The primitive stapedial artery is not part of the embryonic carotid-vertebrobasilar anastomoses. A persistent vessel may arise from the caroticotympanic or inferior tympanic arteries at the level of the carotid canal and course along the cochlear promontory or through or parallel to the facial nerve canal. (E) A persistent pro-atlantal artery arises from the internal (type 1) or external (type 2) carotid artery and communicates with a vertebral artery. It rarely may arise from the common carotid artery.
154
A 50-year-old woman is brought to the hospital with altered mental status and a vertical gaze palsy. Diffusion-weighted MRI sequences (b = 1,000) are shown in these images. What is the patient’s likely diagnosis? A. Bithalamic glioma B. Percheron artery infarct C. Deep venous thrombosis D. Top of the basilar syndrome
B. Percheron artery infarct ## Footnote In the MRI scans shown accompanying the question, there is restricted diffusion with very high signal in a particular arterial territory involving the paramedian thalami bilaterally as well as the rostral midbrain, consistent with Percheron artery territory infarcts. Although there is some variability, the paramedian arteries arise from the posterior cerebral arteries and supply this particular thalamic territory (in some patients they also may supply the anterior polar regions). The artery of Percheron is an anatomic variant, whereby a single artery supplies both paramedian thalamic territories. There is variable blood supply to the rostral midbrain, which may or may not be involved. (A) Bithalamic gliomas are rare and would not be restricted to the territory of the paramedian thalamic arteries or explain involvement of the rostral midbrain. (C) Deep venous thrombosis can result in diffuse swelling of the deep gray nuclei, but would not lead to the particular arterial territorial pattern of this case. (D) Top of the basilar syndrome occurs when a thrombus lodges at the distal basilar artery occluding both posterior cerebral arteries. This can result in occlusion of the paramedian thalamic arteries but likely will result in infarction of other posterior cerebral artery territories, which do not appear involved in this case.
155
A 35-year-old woman with acute myelopathy has evidence of longitudinally extensive signal abnormality involving most of the cervical cord, with patchy areas of enhancement on a spine MRI. An MRI of the brain shows white matter lesions with “cloud-like” enhancement, “pencil-thin” ependymal enhancement, and abnormal T2/FLAIR signal in the optic chiasm and prechiasmatic optic nerves. What is an additional expected finding in this disease process? A. Dawson fingers B. Hilar adenopathy C. Enhancement of ventral cauda equina roots D. Aquaporin-4 IgG seropositivity E. Decreased levels of B12
D. Aquaporin-4 IgG seropositivity ## Footnote Antibodies against the aquaporin-4 (AQP4) channels are highly specific for neuromyelitis optica (NMO). Lesions in NMO characteristically are found in areas of high AQP4 channel expression, such as around the ventricles, cerebral aqueduct, and dorsal midbrain. White matter lesions with “cloudlike” enhancement and “pencil-thin” ependymal enhancement also have been described and are thought to be relatively characteristic. NMO typically results in longitudinally extensive spinal cord signal abnormalities that may show enhancement. Optic neuritis typically is more severe in NMO than in multiple sclerosis. (A) Dawson fingers are demyelinating lesions seen in multiple sclerosis that are oriented radially from the lateral ventricles. Multiple sclerosis usually causes small lesions in short segments of the cord and does not result in longitudinally extensive signal abnormalities. The other features depicted on the MRI of the brain are not consistent with multiple sclerosis. (B) Hilar adenopathy can be seen in sarcoidosis. Neurosarcoid can present as leptomeningeal or parenchymal disease with formation of noncaseating granulomas. (C) Enhancement of ventral cauda equina roots characteristically is seen in Guillain-Barré syndrome, which does not involve the spinal cord or brain. (E) Decreased levels of B12 can result in subacute combined degeneration, which affects the posterior and sometimes lateral columns of the cord. There may be associated contrast enhancement.
156
A patient is reported to have a “string of pearls” appearance on his angiogram. What is the likely diagnosis? A. Severe carotid artery stenosis B. Dural arteriovenous fistula C. Fibromuscular dysplasia D. Arteriovenous malformation E. Carotid artery dissection
C. Fibromuscular dysplasia ## Footnote Both fibromuscular dysplasia and central nervous system vasculitis can be described as a “string of pearls” on angiogram. (A, E) Both severe carotid artery stenosis and dissection can be described as displaying a “string sign.” (B) Dural arteriovenous fistulae are described as having “retrograde cortical venous drainage,” implying the need for intervention. (D) Arteriovenous malformations characteristically display early draining veins.
157
What is correct regarding the imaging features of hangman fractures according to the Effendi classification (as modified by Levine and Edwards)?What is correct regarding the imaging features of hangman fractures according to the Effendi classification (as modified by Levine and Edwards)? A. Type 4 fractures present with severe angulation and displacement and facet dislocation. B. Type 2a fractures present with minimal displacement and severe angulation. C. Type 1 fractures present with severe displacement and no angulation. D. Type 3 fractures present with severe displacement and severe angulation without facet dislocation
B. Type 2a fractures present with minimal displacement and severe angulation. ## Footnote Type 2a fractures (modification proposed by Levine and Edwards) present with severe angulation (more than 11 degrees) but minimal or no significant translation or displacement and are most commonly due to flexion-distraction injuries. Type 2 (not type 2a) fractures are associated with significant displacement (more than 3 mm) and angulation (more than 11 degrees) with translation of the anterior fragment and disruption of the C2-C3 intervertebral disk space. These are secondary to hyperextension, axial loading, and rebound flexioncompression. (A) There is no type 4 fracture in the modified Effendi grading system. (C) Type 1 fractures are hairline fractures of the ring of the axis, with no significant translation and no angulation between C2 and C3. They are the result of hyperextension and axial loading. (D) Type 3 fractures present with severe angulation and displacement of the anterior fragment with unilateral or bilateral facet dislocation, and they result from a flexioncompression injury. There is fracture of the posterior elements.
158
An arteriogram is performed, and the report mentions that an infundibulum is present. What is a lesion consistent with this finding? A. 3-mm funnel-shaped segment at the posterior communicating artery origin B. Triangular-shaped segment more than 3 mm from the origin of the anterior communicating artery C. Spherical dilation of the basilar artery tip D. 3- to 4-mm focal dilation located adjacent to the anterior choroidal artery E. Narrow-necked 7-mm middle cerebral artery aneurysmal dilation
A. 3-mm funnel-shaped segment at the posterior communicating artery origin ## Footnote An infundibulum classically is less than 3 mm at its widest portion, triangular in shape, with a vessel arising from its apex, and almost always is located at the origin of the posterior communicating artery. They are not uncommon to find, and although they can grow into an aneurysm, an infundibulum in itself is not classically associated with rupture. (B, E) A diameter greater than 3 mm would be too large for an infundibulum. By definition, there also should be a normal vessel arising from its apex. (C) A spherical dilation of the basilar artery tip is the definition of a basilar tip aneurysm and not an infundibulum. (D) Infundibula arise at the origin of a vessel and not adjacent to it (as can occur with a saccular aneurysm). Additionally, size greater than 3 mm would be too large for an infundibulum.
159
What is a characteristic of the lesion shown on these pre- and postcontrast CT images? A. It is treated primarily with open microsurgery. B. It has a lower rate of hemorrhage compared with anterior circulation lesions. C. It hemorrhages primarily into the interhemispheric fissure. D. The apex is the most common location.
D. The apex is the most common location. ## Footnote The apex (tip) is the most common location of basilar artery aneurysms, and lesions at this site represent 50 to 80% of all posterior fossa aneurysms. Aneurysms of the basilar trunk are rare. Other locations for basilar artery aneurysms include the junctions of the posterior cerebral, anterior inferior cerebellar, and superior cerebellar arteries. (A) Endovascular therapy the is mainstay for treating basilar tip aneurysms and largely has replaced traditional microsurgical techniques, which necessitate significant brain retraction and temporary arterial occlusion that may result in significant morbidity or mortality. (B) Posterior circulation aneurysms have the highest rate of rupture of all intracranial aneurysms. Basilar and internal carotid artery aneurysms also may be more likely to grow compared with aneurysms developing at other sites. (C) The epicenter of subarachnoid hemorrhage may suggest the site of the aneurysm. Anterior communicating artery aneurysms bleed primarily into the interhemispheric fissure, and those from the middle cerebral artery hemorrhage bleed into the sylvian fissure. Basilar tip aneurysms characteristically bleed into the basilar cisterns, posterior third ventricle, and fourth ventricle. That being said, hemorrhage frequently is widespread without a discernible pattern.
160
The lesion illustrated on this MR image (arrow) showed syncytial and epithelial cells with indistinct cytoplasmic borders and whorl-like structures on histopathological analysis. What is the diagnosis represented? A. Hemangiopericytoma B. Lymphoma C. Schwannoma D. Meningioma
D. Meningioma ## Footnote The pathological description provided in the question is that of a meningioma. Meningiomas represent the most common primary intracranial tumors in adults and most frequently are parafalcine or seen along the sphenoid wings. About 10% occur in the parasellar region. Meningiomas can arise primarily within the cavernous sinus or involve it secondarily. The patient’s presentation depends on the neurovascular structures involved. Patients commonly present with oculomotor, visual, or trigeminal symptoms. (A) Hemangiopericytomas are rare intracranial lesions. Microscopically, one can find uniform spindle cells with intratumoral staghorn vessels. On imaging, they commonly present as a large and aggressive duralbased mass. (B) Secondary lymphomas are more common than primary lymphomas in the central nervous system. The great majority of primary central nervous system lymphomas are of the B-cell type and occur in the parenchyma. Most secondary lymphomas affect the leptomeninges but also may occur in the brain. Dural lymphomas are rare. (C) Schwannomas arise from Schwann cells and are seen in adults. Microscopic exam shows spindle cells with ill-defined cytoplasm and dense chromatin sometimes associated with Verocay bodies. Intracranial schwannomas most commonly are related to the vestibular nerve followed by the trigeminal and facial nerves. In the parasellar region, trigeminal schwannomas predominate
161
What is the origin of the lesion depicted on these MR images? A. Embryonic endoderm B. Embryonic ectoderm C. Notochord D. Mesoderm E. Arachnoid cap cells
A. Embryonic endoderm ## Footnote This is the characteristic location of a colloid cyst, which derives from embryonic endoderm and nearly always is situated in the anterosuperior aspect of the third ventricle. These lesions may be associated with obstruction of the foramina of Monro, which can be acute and lead to rapid herniation and death. They often are hyperdense on CT, and their MRI signal characteristics vary depending on the degree of proteinaceous contents; those with lower T2 signal tend to be more viscous. The cyst is bright on both the noncontrast T1-weighted and FLAIR images shown in this case. (B, D) Colloid cysts derive from embryonic endoderm. (C) Tornwaldt cysts, among other lesions, are derived from the notochord. (E) Arachnoid cap cells give rise to meningiomas.
162
What is a characteristic of the pericallosal lesion on these MR images of the brain? A. Arises from arachnoid cap cells B. Calcification is common C. Contains dermal appendages D. Demonstrates an alanine peak on MR spectroscopy
B. Calcification is common ## Footnote The location and homogeneously bright T1 signal intensity of the mass displayed along with signal suppression on the fat-saturated T2 image are most consistent with a pericallosal lipoma (tubulonodular type). Note that the image to the left is without intravenous contrast (there is no mucosal enhancement in the nasopharynx or pituitary gland). Calcification is common, particularly when there is callosal dysgenesis, which is associated more frequently with tubulonodular lipomas. Curvilinear lipomas have a low incidence of associated anomalies. Note arachnoid cysts posterior to the corpus callosum and in the posterior fossa compressing the cerebellum. The callosal splenium is short. (A) Meningiomas arise from arachnoid cap cells. Lipomas develop from anomalous differentiation of the meninx primitiva. (C) Dermoids contain dermal appendages. Although they characteristically show areas of fat signal intensity, they are more heterogeneous than lipomas and commonly show dark areas of T2 hypointensity and fluid–fat levels. Dermoids have a predilection for the midline, whereas lipomas tend to occur along infoldings of the subarachnoid space. (D) Meningiomas demonstrate an alanine peak on MR spectroscopy at short TE values.
163
The head CT shown in this image is compatible with what pathology: A. Abscess B. Neoplasm C. Acute infarct D. Contusion E. Old infarct
C. Acute infarct ## Footnote There is hypoattenuation involving the left insula and lateral basal ganglia in a patient with an acute middle cerebral artery infarct. Note two hyperdense dots in the left sylvian fissure (the “MCA dot” sign), consistent with thrombosed M2 branches. (A) There is no defined fluid collection to suggest an abscess. (B) An infiltrative neoplasm potentially can mimic an infarct particularly on CT. (D) Contusions in a patient with trauma usually are peripheral and cortical but may vary in size and involve the subcortical white matter. They do not follow a vascular distribution and would not explain the hyperdense vessels. (E) Old infarcts usually show lower attenuation and well-circumscribed margins, with variable degrees of volume loss and wallerian degeneration.
164
A man with lethargy, confusion, and one episode of seizures underwent an MRI of the brain, shown in these images. What is the likely diagnosis? A. Infiltrative glioma B. Acute infarct C. Osmotic demyelination D. Brainstem encephalitis
C. Osmotic demyelination ## Footnote The axial FLAIR image accompanying the question shows a triangular hyperintensity in the mid-posterior pons that demonstrates peripheral enhancement on the coronal postcontrast image. This is a characteristic location and presentation for osmotic demyelination, which commonly is seen in alcoholics after rapid correction of hyponatremia, as well as in advanced liver disease, various causes of malnutrition, and burns. Fifty percent of patients show abnormalities in the pons, and the rest of the lesions are extrapontine, occurring in the basal ganglia, thalami, brainstem, and corpus callosum. Lesions usually do not enhance, although ring enhancement of pontine lesions has been observed in the acute phase, as in this case. (A) An infiltrative glioma would have some degree of mass effect. The discrete central location and triangular configuration of the lesion in this case is more consistent with osmotic demyelination. (B) Infarction usually does not cross the midline except for some infarcts from perforator vessels. The triangular shape and central location of the lesion in this case are much more likely to be related to osmotic demyelination. (D) Edema associated with brainstem encephalitis likely would show mass effect and would be either asymmetric or diffuse.
165
A woman complaining of neck pain undergoes a cervical spine CT. The exam shows a 1.5-cm lucent vertebral lesion with a calcified core and surrounding sclerosis. What is a characteristic of this lesion? A. Increased incidence in the elderly B. More commonly develops along the end plates C. Shows increased uptake on bone scintigraphy D. Pain increases with activity
C. Shows increased uptake on bone scintigraphy ## Footnote These findings are most consistent with an osteoid osteoma with a lucent nidus, a calcified center, and surrounding sclerosis. These lesions typically show increased uptake on bone scintigraphy, on which they may appear as a “double density” with marked central uptake and a surrounding rim of relatively lower uptake. (A) Osteoid osteomas usually occur in adolescents and young adults, and more commonly present in the second decade of life. There is growing evidence that osteoid osteomas resolve over time. (B) Osteoid osteomas commonly occur in the long bones. In the spine, they usually involve the posterior elements and are most frequently seen in the lumbar followed by cervical spine. (D) With osteoid osteomas, pain typically is worse at night, relieved with aspirin (osteoid osteomas produce prostaglandins), and is not related to activity.
166
An infant involved in a motor vehicle collision is brought to the emergency department where he underwent a CT examination of the head, shown in this image. There is no evidence of intracranial hemorrhage, and the patient is neurologically intact. What is a characteristic of this patient’s lesion? A. Immediate surgical elevation is warranted. B. There is an increased risk of dural tears. C. Elevation decreases the incidence of posttraumatic seizures. D. There is a low risk of cortical laceration. E. It represents the most common type of pediatric skull fracture.
B. There is an increased risk of dural tears. ## Footnote Depressed skull fractures are associated with an increased risk of dural tears. (A) Most pediatric skull fractures can be managed expectantly if they are depressed less than 1 cm, they are closed, there is no associated intracranial hemorrhage, and the patient is neurologically intact. (C) There is no evidence that surgical elevation decreases the incidence of posttraumatic seizures, as any potential cortical damage occurs at the time of injury (D) Depressed skull fractures have an increased risk of cortical laceration. (E) Linear fractures are the most common type of skull fractures, followed by depressed and basilar fractures.
167
An MRI of the orbits shows a “tram track” sign. What is a characteristic of this lesion? A. It is a small round blue cell tumor. B. It is associated with neurofibromatosis type 1. C. It derives from arachnoid cap cells. D. It is related to deposition of mucopolysaccharides.
C. It derives from arachnoid cap cells. ## Footnote Meningiomas can result in thickening and enhancement along the optic nerve sheath in a parallel configuration resembling a tram track. They derive from arachnoid cap cells. (A) A retinoblastoma is a highly malignant small round blue cell tumor. It does not produce the so-called tram track sign. Retinoblastomas commonly show low intensity on T2-weighted sequences and profound restricted diffusion due to their high cellularity. (B) Optic pathway gliomas can either be sporadic or associated with neurofibromatosis type 1. Those that are syndromic more commonly involve the optic nerves than the optic chiasm or postchiasmatic tracts. MRI shows expansion of the optic nerve due to tumor infiltration with variable degrees of contrast enhancement. (D) Thyroid orbitopathy is related to leukocytic infiltration with deposition of mucopolysaccharides. It can affect any extraocular muscle with preferential involvement of the inferior, medial, and superior extraocular muscles.
168
A contrast-enhanced T1-weighted MR image of the thoracic spine is shown here. What is the likely diagnosis? A. Epidermoid B. Traumatic pseudomeningocele C. Arachnoid cyst D. Neurenteric cyst
D. Neurenteric cyst ## Footnote This is a complex, cystic lesion with a component projecting into and expanding the spinal canal and a second component projecting into the posterior mediastinum. The inferior aspect of the lesion is partially intramedullary. Note also congenital vertebral anomalies with incomplete segmentation and a small size of multiple adjacent thoracic vertebrae. This constellation of findings is most consistent with a neurenteric cyst. These lesions result from incomplete resorption of the neurenteric canal, and when they occur in the spine, they are most commonly thoracic. (A) Epidermoid tumors in the spine may be developmental or acquired, and occur most commonly in the lumbar region. They rarely may be associated with spinal malformations such as hemivertebrae. (B) A traumatic pseudomeningocele would not result in congenital vertebral anomalies, and its contents would follow cerebrospinal fluid signal on all sequences. (C) An arachnoid cyst is not associated with vertebral anomalies, although it could result in osseous remodeling due to slow growth.
169
What normal intracranial component demonstrates high signal intensity on a T1-weighted sequence of the brain? A. Unmyelinated white matter B. Melanin C. High vascular flow D. Deoxyhemoglobin
B. Melanin ## Footnote Melanin has a high affinity for many metals including iron, manganese, copper, and zinc, and their paramagnetic effects result in T1 shortening; therefore, melanin is bright on T1-weighted sequences. (A) Myelin is bright on T1-weighted images due to the decreased motion of water molecules associated with macromolecules such as myelin. T1 images are helpful in the evaluation of myelination in infants. (C) High vascular flow results in a flow void and therefore looks dark on T1-weighted sequences. (D) Deoxyhemoglobin is seen in acute hemorrhage. There is no significant effect on T1 signal as the three-dimensional configuration of deoxyhemoglobin does not allow access of water molecules to the paramagnetic iron atoms, which prevents the dipole–dipole interactions that would result in T1 shortening.
170
In the setting of a large extra-axial hematoma or other significant supratentorial space-occupying lesion, the Kernohan notch phenomenon refers to: A. Contralateral hydrocephalus secondary to obstruction of the foramen of Monro B. Compression of the ipsilateral cerebral peduncle against the cerebellar tentorium C. Compression of the anterior cerebral artery against the falx cerebri D. Compression of the contralateral cerebral peduncle against the cerebellar tentorium
D. Compression of the contralateral cerebral peduncle against the cerebellar tentorium ## Footnote The Kernohan notch phenomenon (also known as a “false localizing sign” and the KernohanWoltman notch) is a result of supratentorial mass effect with extensive shift of midline structures, resulting in compression of the contralateral cerebral peduncle against the cerebellar tentorium. This manifests clinically as hemiplegia or hemiparesis ipsilateral to the primary lesion. (A) Contralateral hydrocephalus secondary to obstruction of the foramen of Monro can be seen as a complication of supratentorial mass effect. (B) The Kernohan notch phenomenon refers to compression of the contralateral (not ipsilateral) cerebral peduncle against the cerebellar tentorium. (C) Compression of the anterior cerebral artery against the falx cerebri can occur with subfalcine herniation, as the cingulate sulcus is displaced beyond the midline
171
The lesions demonstrated on these MR images likely represent: A. Acute demyelination B. Metastases C. Multifocal glioblastoma D. Multifocal abscesses E. Vasculitis
A. Acute demyelination ## Footnote These lesions demonstrate the typical appearance of acute tumefactive demyelination: concentric rings of different intensities on the FLAIR image, a periventricular configuration along perimedullary veins (somewhat perpendicular to the lateral ventricles), and, most importantly, an incomplete ring of enhancement on the postcontrast T1 images. (B) Metastases are a cause of multifocal enhancing lesions, but the presence of incomplete ring enhancement would be unusually rare, as would be the perimedullary configuration of the lesions (metastases favor the gray matter–white matter junction and vascular border zones). In addition, metastases likely would incite a significant amount of surrounding edema for the size of these lesions. (C) Multifocal glioblastoma likely would have a more heterogeneous and infiltrative appearance rather than the discrete lesions in the distribution described above. (D) Multifocal abscesses would not present with an incomplete ring of enhancement, and the perimedullary/ periventricular distribution seen in this case would be unusual for abscesses. Abscesses also demonstrate central restricted diffusion, whereas tumefactive demyelination may demonstrate restricted diffusion peripherally. (E) Vasculitides can result in multifocal white matter lesions and infarcts. Mural enhancement sometimes can be demonstrated on high-resolution vessel wall imaging. An incomplete ring enhancement is not seen.
172
What is the line that is drawn along the clivus and extrapolated posteroinferiorly to the upper cervical spinal canal? A. McRae line B. Chamberlain line C. Wackenheim line D. McGregor line
C. Wackenheim line ## Footnote The Wackenheim (basilar) line is drawn along the clivus and extends inferiorly to the cervical spinal canal. It should be tangential to the dorsal surface of the tip of the odontoid process. Transection of this line by the odontoid process indicates basilar invagination.
173
What is the line that connects the basion to the opisthion? A. McRae line B. Chamberlain line C. Wackenheim line D. McGregor line
A. McRae line ## Footnote The McRae line is drawn from the basion to the opisthion and marks the level of the foramen magnum. The odontoid process normally is located inferior to this line, and its extension above it indicates basilar invagination. (B) The Chamberlain line extends from the posterior pole of the hard palate to the opisthion. Extension of the odontoid process greater than 3 mm beyond this line indicates basilar invagination. (D) The McGregor line is a modification of Chamberlain line developed for cases where the opisthion could not be identified in radiographs. The McGregor line extends from the posterior pole of the hard palate to the most inferior aspect of the occipital curvature. Greater than 4.5 mm extension of the odontoid process beyond this line indicates basilar invagination.
174
A 55-year-old man became confused and hypotensive following a diagnostic angiographic procedure with difficult groin access. Emergent CT of the head was noncontributory. A noncontrast CT of the abdomen is shown here. What is the patient’s most likely diagnosis? A. Urinoma B. Bowel infarction C. Ascites D. Hematoma
D. Hematoma ## Footnote The noncontrast CT image accompanying the question shows a large and heterogeneous retroperitoneal mass on the left side, with areas that are hyperdense relative to the adjacent psoas muscle, consistent with a retroperitoneal hematoma. This is an infrequent but important complication with a reported incidence between 0.5% and 5% that can be seen following difficult arterial or venous groin access, particularly in patients who are anticoagulated. (A) An urinoma would not be expected after femoral puncture. It also would appear more homogeneous and demonstrate lower density on CT unless it was infected. (B) The image shows a retroperitoneal process that is displacing the bowel loops anteriorly. (C) The image shows fluid that is not within the peritoneal cavity. The location of this hematoma is retroperitoneal, which can be suspected following difficult groin access and also by noticing mild enlargement of the left psoas muscle and stranding of the surrounding retroperitoneal fat.
175
What is a characteristic of the lesion depicted in this CT image? A. Limited by sutures B. Usually crosses the midline C. Most commonly due to an arterial injury D. Occurs between the inner and outer layers of the dura E. Limited by dural reflections
E. Limited by dural reflections ## Footnote This is an acute subdural hematoma with hyperdense blood, resulting in a shift of midline structures. These lesions occur between the inner layer of the dura and arachnoid membranes, and therefore are limited by dural reflections including the falx cerebri and tentorium cerebelli. (A) Epidural, not subdural, hematomas occur between the outer layer of the dura and the calvaria and are thus limited by tight dural attachments at the sutures. (B) Supratentorial subdural hematomas cannot cross the midline, as they are limited by the dural reflections that form the falx cerebri. (C) Subdural hematomas are most commonly due to the tearing of bridging veins due to a shearing injury. For this reason, they are more common in older brains where these veins may be stretched due to cerebral atrophy. (D) Subdural hematomas occur between the dura and arachnoid membranes.
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What is a characteristic of oligodendrogliomas? A. It is more common in the occipital lobes. B. Calcification is present in 10% of cases. C. High cerebral blood flow on perfusion MRI correlates with high histological grade. D. Preferential involvement of the cortex is a distinctive feature. E. Tumors with 1p/19q deletions respond poorly to treatment.
D. Preferential involvement of the cortex is a distinctive feature. ## Footnote Preferential involvement of the cortex is one of the distinctive features of oligodendroglial tumors. (A) Oligodendrogliomas occur most commonly in the frontal lobes, followed by the temporal and parietal lobes. Occipital involvement is relatively rare. (B) Calcification is a common feature of oligodendrogliomas and is found in 70 to 90% of cases. Cystic degeneration and hemorrhage may be seen occasionally. (C) In contrast to astrocytic brain tumors, perfusion-weighted imaging has had limited value in differentiating subgroups of oligodendrogliomas with significant overlap between low- and high-grade histologies. Low-grade oligodendrogliomas can present with increased perfusion. (E) Oligodendrogliomas with 1p/19q co-deletions respond more favorably to both radiation and chemotherapy, and this is the most important factor associated with improved survival
177
A man with sickle cell disease and secondary moyamoya-type vascularity underwent an MRI study of the brain, which demonstrates an “ivy” sign. This sign is related to: A. Pial collateral circulation B. Leptomeningeal carcinomatosis C. Meningitis D. Cerebral microhemorrhages E. Areas of acute ischemia
A. Pial collateral circulation ## Footnote Patients with moyamoya-type vascularity may develop pial collaterals due to chronic occlusion. MRI shows nonsuppression of FLAIR signal in sulci and perivascular spaces, which may be accompanied by contrast enhancement. (B) Leptomeningeal carcinomatosis can show FLAIR nonsuppression but is not associated with an “ivy” sign and would not be an expected complication, given the patient’s clinical history. (C) Meningitis can result in leptomeningeal enhancement and FLAIR nonsuppression. (D) Cerebral microhemorrhages are a complication of sickle cell disease and may be related to embolism of marrow fat or local thrombosis with subsequent hemorrhage. (E) Ischemia is one of the known complications of sickle cell disease. The cause is multifactorial and includes hypercoagulability, endothelial injury, and development of moyamoya type vessels.
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What imaging feature favors a pilocytic astrocytoma over a hemangioblastoma? A. High relative cerebral blood volumes B. Presence of small vascular flow voids C. Enhancing nodule abutting the pia D. Enhancement of the cyst wall
D. Enhancement of the cyst wall ## Footnote Enhancement of the cyst wall may be present in pilocytic astrocytomas, whereas the wall of a hemangioblastoma should not enhance. Two thirds of hemangioblastomas are cystic with an enhancing mural nodule, and one third is solid. (A) Hemangioblastomas are highly vascular lesions with relative cerebral blood volumes that are significantly higher than pilocytic astrocytomas. (B) Hemangioblastomas often have small vascular flow voids due to hypervascularity. (C) An enhancing nodule abutting the pia is characteristic of a hemangioblastoma.
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What characteristic neuroimaging feature has been described in angiocentric gliomas? A. Enhancing nodule abutting the meningeal surface B. Bubbly appearance on T2 images C. Intrinsic T1 hyperintensity D. Triangular morphology
C. Intrinsic T1 hyperintensity ## Footnote Angiocentric gliomas are relatively indolent and slow-growing cortical masses that initially were included in the WHO classification of central nervous system tumors in 2007. Intrinsic T1 hyperintensity is suggestive of the diagnosis, but such a feature is present inconsistently. They usually do not enhance. (A) Pleomorphic xanthoastrocytomas occur most commonly in the temporal lobes and typically have an enhancing solid component abutting the meningeal surface. (B) A usually nonenhancing cortical/subcortical mass with a bubbly appearance on T2 and FLAIR images is most consistent with a dysembryoplastic neuroepithelial tumor. (D) A triangular morphology sometimes has been described in dysembryoplastic neuroepithelial tumors.
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A 17-year-old boy is brought to the emergency department with dysarthria and ataxia. An MRI of the brain shows increased T2/FLAIR signal and restricted diffusion involving the lateral putamina and tectum. On clinical exam, he has peripheral brownish rings in his corneas, and the liver function tests are elevated. Mutations in what gene likely is involved in this patient’s disease process? A. ATP7B B. NOTCH3 C. SMARCB1 D. FGFR E. PTEN
A. ATP7B ## Footnote The findings described in the question are compatible with Wilson disease (hepatolenticular degeneration). The clinical exam describes the Kayser-Fleischer rings that are present in 98% of patients with neurologic manifestations. The imaging findings show the typical distribution of signal abnormalities in the basal ganglia and midbrain, with sparing of the red nuclei and substantia nigra. Wilson disease results from mutations in the ATP7B gene that leads to a ceruloplasmin deficiency and copper accumulation in the liver, brain, and corneas. (B) Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) has been linked to mutations in the NOTCH3 gene. (C) Mutations in the SMARCB1 gene can lead to Coffin-Siris syndrome and to an increased risk of developing rhabdoid tumors such as ATRT. (D) Most syndromic cases of trigonocephaly are related to mutations in the FGFR genes. (E) Cowden disease (multiple hamartoma syndrome) has been linked to loss of PTEN gene function.
181
The “eye of the tiger” sign is described on an MRI of the brain. This is seen in what entity? A. Pantothenate kinase–associated neurodegeneration B. Huntington disease C. Wilson disease D. Carbon monoxide intoxication
A. Pantothenate kinase–associated neurodegeneration ## Footnote Pantothenate kinase–associated neurodegeneration is a rare disorder caused by mutations in the PKAN2 gene that result in abnormal iron accumulation in the brain, particularly in the globi pallidi and substantia nigra. Patients present in the first or second decades of life with symptoms including progressive dystonia, dementia, choreoathetosis, and rigidity. The “eye of the tiger” sign classically is described on T2-weighted images, with central hyperintensity representing demyelination and gliosis surrounded by dark areas of iron deposition. (B) The characteristic imaging finding of Huntington disease is atrophy of the heads of the caudate nuclei, resulting in ballooning of the frontal horns of the lateral ventricles. The putamina also can show volume loss, and there may be increased T2/FLAIR signal in the basal ganglia. (C) Wilson disease shows increased signal in the basal ganglia, particularly in the lateral putamina, and brainstem, typically with sparing of the red nuclei and substantia nigra, leading to the “face of the giant panda” sign. (D) Carbon monoxide intoxication may show increased signal in the globi pallidi and white matter.
182
A woman with multiple cranial neuropathies undergoes an MRI of the brain, which shows a wellcircumscribed mass in the cavernous sinus. The lesion has areas of profound T2 hypointensity and prominent band-like artifact propagating along the phase encoding direction. What is the patient’s likely diagnosis? A. Aneurysm B. Meningioma C. Chordoma D. Chondrosarcoma
A. Aneurysm ## Footnote Areas of profound T2 hypointensity in a wellcircumscribed skull base region mass should raise concern about an aneurysm. The presence of pulsation artifact propagating along the phase-encoding direction makes this lesion an aneurysm until proven otherwise. Other sources of phase-encoding motion artifact are swallowing, breathing, peristalsis, and patient movement during the scan. (B) Meningiomas are relatively hypointense on T2-weighted images and can have irregular areas of marked hypointensity due to calcification or occasionally hemorrhage. They do not result in a phase-encoding artifact. (C, D) Chordomas and chondrosarcomas characteristically are bright on T2 images. They are not associated with pulsation artifacts.
183
A patient is noted to have “harlequin-eye” deformities on a craniofacial CT. What cranial suture is fused? A. Sagittal B. Coronal C. Lambdoid D. Metopic
B. Coronal ## Footnote Premature fusion of the coronal sutures can result in the so-called harlequin-eye deformity, which may be unilateral or bilateral. Approximately 10% of craniosynostoses are syndromic and may be related to mutations involving the FGFR and TWIST-1 genes, among others. Syndromic associations include Crouzon, Apert, and Pfeiffer syndromes. (A) Fusion of the sagittal suture leads to scaphocephaly. (C) Lambdoid synostosis is rare and results in flattening of the posterior head ipsilaterally. (D) Metopic craniosynostosis gives an abnormal triangular shape to the forehead (trigonocephaly), sometimes with the development of a frontal osseous ridge.
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A 52-year-old woman with a history of decompressive left hemicraniectomy for a large middle cerebral artery territory infarction presents with new-onset headache, vomiting, and lethargy. Her CT scan is shown in this image. What is the next appropriate step for her management? A. Cranioplasty B. Surgical evacuation C. Contralateral craniectomy D. Lumbar spinal fluid drain
A. Cranioplasty ## Footnote “Sunken skin flap” or “trephine” syndrome refers to an uncommon late postoperative complication following decompressive craniectomy in which there is marked concavity of the skin flap and paradoxical cerebral herniation. The pathophysiology is presumed to be related to exposure of the intracranial contents to atmospheric pressure and a negative pressure gradient that may be exacerbated by cerebrospinal fluid hypovolemia. Neurologic deterioration in this context is a surgical emergency, and the goal of treatment is to restore intracranial pressure, which generally can be achieved by cranioplasty. Other measures include placing the patient in the Trendelenburg position, tilting the head toward the craniectomy site, an epidural blood patch, or clamping the ventricular shunt tubing. (B) There are no collections to evacuate in this patient. (C) Contralateral craniectomy would not help restore the intracranial pressure. (D) Lumbar spinal fluid drain would be contraindicated in a patient with a herniation syndrome. Lumbar epidural blood patches may be useful in the management of sunken flap syndrome
185
What feature favors a spinal cord ependymoma over an astrocytoma? A. Association with neurofibromatosis type 1 B. Ill-defined margins C. Heterogeneous enhancement D. Central location
D. Central location ## Footnote Ependymomas tend to have a central location, although such distinction usually is difficult to make and is not possible with large tumors. Ependymomas more commonly present with cysts, calcifications, and hemorrhage. (A) Patients with neurofibromatosis type 2 have an increased incidence of ependymomas, which occur most frequently in the brainstem and spinal cord. (B) Illdefined margins more commonly are present in spinal cord astrocytomas. Ependymomas usually are well defined. (C) Heterogeneous enhancement can be seen in both astrocytomas and ependymomas and is not a helpful discriminating feature.
186
A man was brought to the emergency room following a high-speed motor vehicle collision. CT of the cervical spine showed a fracture of the pars interarticularis of C2 bilaterally. What finding would indicate an unstable fracture? A. More than 2 mm between fragments B. Greater than 10 degrees of angulation C. Subluxation of C2 on C3 D. Lateral offset more than 6 mm
C. Subluxation of C2 on C3 ## Footnote The findings describe a hangman fracture, which most commonly is secondary to hyperextension, compression, and distraction. Subluxation of C2 on C3 indicates an unstable fracture. (A, B) Hangman fractures with more than 3 mm between fragments and more than 15 degrees of angulation are considered unstable. (D) In patients with a Jefferson fracture, a combined offset of the lateral C1 masses relative to C2 greater than 6 mm suggests disruption of the transverse ligament and an unstable fracture
187
A lumbar spine radiograph from a patient with a history of posterior spinal fusion surgery and progressive back pain is shown in this image. What surgical procedure is indicated? A. Hardware removal due to diskitis/osteomyelitis B. Pedicle subtraction osteotomy C. Hardware revision due to loosening D. Anterior interbody fusion
B. Pedicle subtraction osteotomy ## Footnote This patient has sagittal imbalance due to loss of the expected lumbar lordosis, with acute kyphotic angulation centered at L1 above the level of the fusion. A pedicle subtraction osteotomy at L1 potentially could restore lordosis by means of a wedge-shaped vertebral resection and shortening of the posterior column. (A) Although other modalities such as MRI are more sensitive, there is no radiographic evidence of diskitis/osteomyelitis that would manifest as erosive changes centered at the disk space with variable degrees of end-plate and vertebral destruction. (C) There is no visible perihardware lucency to suggest loosening on this exam. (D) Anterior interbody fusion would not restore lumbar lordosis.
188
What is a characteristic of Sturge-Weber syndrome? A. Multifocal arteriovenous malformations B. Port-wine stain along the cranial nerve VII distribution C. Glioneuronal hamartomas D. Progressive hemifacial atrophy E. Sporadic presentation
E. Sporadic presentation ## Footnote Sturge-Weber syndrome presents sporadically without a definite hereditary pattern identified to date. (A) Sturge-Weber syndrome is a disorder of neural crest cell migration and differentiation. It is characterized by an inadequate control of capillary formation, with the development of leptomeningeal angiomatosis and choroidal angiomas and the recruitment of deep medullary and choroidal veins. Cortical calcifications and cerebral volume loss ipsilateral to the port-wine stain are seen in advanced cases, possibly related to chronic ischemia. Arteriovenous malformations are not seen. (B) The port-wine stain of Sturge-Weber syndrome occurs along the distribution of cranial nerve V. The ophthalmic branch almost always is involved, followed by the maxillary division in frequency. Involvement of the mandibular division almost never occurs in isolation. (C) Glioneuronal hamartomas are known as cortical tubers and are seen in tuberous sclerosis. (D) Progressive hemifacial atrophy (also known as Parry-Romberg syndrome) is characterized by a slow and progressive unilateral atrophy of the skin, bones, and soft tissues of the face. It sometimes is accompanied by volume loss and abnormal signal in the ipsilateral and sometimes contralateral brain
189
A 56-year-old woman with a history of progressive headaches presented after a seizure episode. An MRI examination of the brain was performed, shown in this image. What is an expected imaging feature of the lesion? A. Increased relative cerebral blood volume B. Elevated apparent diffusion coefficient values C. Elevated N-acetylaspartate levels D. Decreased choline levels E. Elevated alanine levels
A. Increased relative cerebral blood volume ## Footnote The necrotic mass shown with heterogeneous enhancement in an adult patient most likely represents a glioblastoma, which may arise de novo or from degeneration of a lower grade glioma. Glioblastomas show increased relative cerebral blood volume and blood flow on MR and CT perfusion studies and increased permeability values on advanced MR imaging. Approximately 10% are multicentric. They may hemorrhage and rarely calcify. (B) Because glioblastomas are highly cellular tumors, their solid components tend to show restricted diffusion and decreased (not elevated) apparent diffusion coefficient values. (C, D) On MR spectroscopy, glioblastomas and other high-grade gliomas show decreased N-acetylaspartate levels (reflecting neuronal loss) and elevated choline levels due to increased cellular turnover. Glioblastomas may show elevated lipid and lactate levels secondary to necrosis. (E) Elevated alanine levels are a characteristic feature of meningiomas on MR spectroscopy.
190
A previously healthy 35-year-old man presented to clinic complaining of new headaches for several months. An MRI examination of the brain revealed a large, extra-axial, heterogeneous, and avidly enhancing supratentorial mass with prominent internal flow voids, corkscrew vessels, parenchymal edema, and erosion of the adjacent bone without hyperostosis. There was no alanine peak on spectroscopy. The tumor was resected and stained positive for vimentin and CD34, with histological analysis demonstrating uniform spindle cells and stag horn vessels. This lesion is consistent with what tumor diagnosis? A. Hemangioblastoma B. Meningioma C. Lymphoma D. Hemangiopericytoma
D. Hemangiopericytoma ## Footnote This constellation of imaging findings and histopathology are consistent with a hemangiopericytoma. Hemangiopericytomas are locally aggressive tumors with a high incidence of recurrence. They occur more commonly in the supratentorial compartment and usually are large at presentation. Distinguishing them from meningiomas by imaging may be difficult, but hemangiopericytoma can be suggested in the setting of an aggressive, highly vascular, heterogeneous, dural-based mass in a relatively younger patient. Hemangiopericytomas also can metastasize (particularly the anaplastic subtype). On MR spectroscopy, they do not show an alanine peak, which is typical of meningiomas. (A) Hemangioblastomas can occur sporadically. They are vascular tumors with avid enhancement and frequently show prominent flow voids. They very rarely occur in the supratentorial compartment, usually are intra-axial or intraventricular, and may grow along the pial surface (rather than the dural surface). (B) Meningiomas can show variable degrees of vascularity and may be difficult to distinguish from hemangiopericytomas by imaging. Meningiomas more commonly are homogeneous and are more likely to result in hyperostosis rather than frank bone erosion, although they also may be invasive and primarily osseous. They tend to occur in patients older than 50 years of age. (C) Dural lymphoma is rare and usually shows avid but homogeneous enhancement on MRI.
191
What is a characteristic of optic pathway gliomas? A. Sporadic gliomas are more frequently chiasmatic or postchiasmatic. B. They are associated with neurofibromatosis type 2. C. Calcification is common. D. Hemorrhage is common. E. Contrast enhancement correlates with tumor grade.
A. Sporadic gliomas are more frequently chiasmatic or postchiasmatic. ## Footnote Syndromic optic pathway gliomas (associated with neurofibromatosis type 1) more frequently involve the optic nerves, whereas sporadic ones more commonly are chiasmatic or postchiasmatic. (B) Optic pathway gliomas are the most common central nervous system neoplasms in neurofibromatosis type 1. (C) Calcification is rare in optic pathway gliomas. Cysts may be present and appear to be more common in sporadic tumors. (D) Hemorrhage is exceedingly rare in optic pathway gliomas. (E) Contrast enhancement in optic pathway gliomas is variable and does not correlate with tumor grade.
192
What is the Evans ratio? A. Ratio of the largest width of the frontal horns divided by the internal diameter of the skull at the same level B. Ratio of the largest width of the temporal horns divided by the largest width of the frontal horns C. Ratio of the largest width of the frontal horns divided by the maximum internal diameter of the skull D. Occipital-frontal circumference divided by age (in months) of the child
C. Ratio of the largest width of the frontal horns divided by the maximum internal diameter of the skull ## Footnote The Evans ratio is defined as the largest width of the frontal horns divided by the maximum internal diameter of the calvaria, with a value ≥ 0.3 being used to document ventriculomegaly as per the current normal pressure hydrocephalus guidelines; however, recent studies have shown significant variability related to the plane of measurement and angulation. (A) The frontal horn ratio is defined as the largest width of the frontal horns divided by the internal diameter of the skull at the same level. (B) Dilatation of the temporal horns more than 2 mm and a frontal horn ratio more than 0.5 have been described as suggestive of hydrocephalus. Other signs that suggest hydrocephalus include ballooning of the frontal horns or third ventricle, transependymal flow, and bowing of the corpus callosum on sagittal images. (D) Occipitalfrontal circumference is followed for every growing child, and abnormalities such as rapid growth, crossing growth curves, growth more than two standard deviations above or below the average, or a head circumference out of proportion to length/ weight should prompt a workup for underlying conditions (e.g., hydrocephalus).
193
What skull lesion shows a lytic lesion without sclerotic margins? A. Hemangioma B. Epidermoid C. Eosinophilic granuloma D. Osteoid osteoma
C. Eosinophilic granuloma ## Footnote Eosinophilic granulomas, plasmacytomas, and multiple myeloma are examples of lytic processes without surrounding sclerosis. (A) Hemangiomas have sclerotic margins in 30% of cases and often have a characteristic “honeycomb” or “star-bust” pattern of trabeculation on skull radiographs. (B) Epidermoids are slow-growing lucent lesions with sclerotic borders. (D) Osteoid osteomas consist of a radiolucent and sometimes calcified nidus with surrounding zones of dense sclerosis.
194
What is Pott’s puffy tumor? A. Osteomyelitis of the skull with subperiosteal abscess B. Tuberculosis of the spine C. Suprasellar tumor associated with moyamoya syndrome D. Dermoid cyst of the skull
A. Osteomyelitis of the skull with subperiosteal abscess ## Footnote Pott’s puffy tumor is characterized by a subperiosteal abscess and osteomyelitis, usually as a complication of frontal sinusitis. Less common causes include mastoiditis, trauma, craniotomy, and intranasal substance abuse (e.g., cocaine and methamphetamines). It has a higher incidence in adolescents but can occur at any age. Pott’s puffy tumor may be complicated by cortical vein or dural sinus thrombosis, epidural abscess, subdural abscess, cerebritis, or brain abscess. (B) Tuberculosis of the spine or tuberculous spondylitis sometimes is referred to as Pott disease. The infection originates in the end plates with subsequent subligamentous spread. There is a higher incidence of extensive paraspinal abscess formation, and the intervertebral disks more often are spared compared with bacterial infections. In addition, Pott disease has a predilection for the vertebral body with sparing of the posterior elements. (C) True (also known as idiopathic) moyamoya disease has the appearance of a “puff of smoke” on angiography due to extensive collateralization in the setting of bilateral carotid artery stenosis. Moyamoya syndrome (secondary moyamoya) is a nonspecific radiographic finding with a similar pattern of collateralization associated with conditions such as neurofibromatosis type 1, Down syndrome, sickle cell disease, and connective tissue disorders, and may be seen after radiation for treatment of sellar or suprasellar tumors. (D) Dermoid cysts originate from epithelial inclusion cysts and may develop in the skull at sites of suture closure. They contain dermal appendages (as opposed to epidermoid cysts) and are lined by keratinized squamous epithelium.
195
What is the typical distribution of T2/FLAIR signal abnormalities in patients with Wilson disease? A. Medial thalami, periaqueductal gray, tectum, and mammillary bodies B. Red nuclei and substantia nigra C. External capsules and temporal poles D. Lateral putamina and tectum E. Globi pallidi, subcortical white matter, hippocampi, and cerebral cortex
D. Lateral putamina and tectum ## Footnote Wilson disease results from a ceruloplasmin deficiency leading to copper accumulation in brain, liver, and corneas. On MRI, T2/FLAIR signal hyperintensity typically affects the midbrain and basal ganglia, particularly the tectum and lateral putamina. The red nuclei and substantia nigra typically are preserved, resulting in the “face of the giant panda” sign on axial imaging. Diffusion restriction may be seen in the acute stage. (A) T2/FLAIR signal hyperintensity in the medial thalami, periaqueductal gray, tectum, and mammillary bodies should prompt the diagnosis of Wernicke encephalopathy. (B) The red nuclei and substantia nigra usually are spared in Wilson disease. (C) The external capsules and temporal poles characteristically are involved in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). (E) Carbon monoxide poisoning classically shows signal abnormalities in the globi pallidi, but the subcortical white matter, hippocampi, and cerebral cortex also may be affected.
196
A man with a dermal sinus tract in the lower back undergoes an MRI of the spine and is found to have a mass in the region of the conus medullaris and cauda equina. What imaging finding would support the diagnosis of superimposed infection of the mass? A. Thickening and enhancement of the cauda equina B. Markedly increased diffusion-weighted imaging signal within the mass C. Increased signal within the mass on the postcontrast T1 sequences D. Signal dropout on gradient echo sequences
A. Thickening and enhancement of the cauda equina ## Footnote Thickening and enhancement of the cauda equina would support the presence of an adjacent inflammatory process or infection. Myelopathy with edema of the distal cord and conus medullaris and pial enhancement may be seen depending on the severity of the infection. (B) Markedly increased diffusion-weighted imaging signal within a mass could be related to restricted diffusion from an abscess, but also can be seen in epidermoids and dermoids due to what is probably a combination of restricted diffusion and T2 shine-through effects. An infected dermoid or epidermoid is accompanied by inflammatory changes such as edema and enhancement of the surrounding tissues. (C) It is important to differentiate whether increased signal on the postcontrast T1 sequences is due to true enhancement or related to intrinsic T1 hyperintensity; therefore, both pre- and postcontrast sequences should be evaluated side by side. Hemorrhage, fatty masses, and certain tumors such as melanomas can show increased T1 signal on the precontrast images. (D) Signal dropout on gradient echo sequences can be seen with prior hemorrhage.
197
An MRI of the lumbar spine shows diffuse and homogeneous thickening and enhancement preferentially involving the ventral nerve roots. What is the likely diagnosis, given these findings? A. Leptomeningeal carcinomatosis B. West Nile virus infection C. Dural arteriovenous fistula D. Sarcoidosis
B. West Nile virus infection ## Footnote Neuroimaging findings in West Nile virus infection are varied and, in the spine, include nonspecific intramedullary signal abnormalities with variable enhancement. Infection can result in progressive ascending paralysis and preferential ventral nerve root enhancement mimicking Guillain-Barré syndrome. (A) Leptomeningeal carcinomatosis is distributed more unevenly and is commonly nodular. Patients may present with “sugar coating” of the spinal cord. (C) Dural arteriovenous fistulas often can be identified by the presence of vascular flow voids surrounding an edematous spinal cord (best seen on T2 sequences). (D) Sarcoidosis can result in leptomeningeal or parenchymal disease with formation of noncaseating granulomas. It does not preferentially involve the ventral nerve roots.