Neurology Cat 1 Flashcards
(39 cards)
1
Q
Dysgenesis of the corpus callosum - definition
A
primary agenesis: the corpus callosum never forms
secondary dysgenesis: the corpus callosum forms normally and is subsequently destroyed
2
Q
Dysgenesis of the corpus callosum: epidemiology
A
1/20 000
M:F = 2:1
Risk factor: maternal alcohol consumption
3
Q
Dysgenesis of the corpus callosum: Clinical presentation
A
Dictated by associated abnormalities
may have dysmorphic faces - hypertelorism
4
Q
Dysgenesis of the corpus callosum: radiographic features - Antenatal Ultrasound
A
third ventricle
-dilated
- can be elevated or dorsally displaced
- may communicate with the interhemispheric cistern
- may project superiorly as a dorsal cyst
- choroid may be seen as an echogenic structure in the roof of the cyst
lateral ventricles
- widely spaced parallel bodies (racing car sign)
- small frontal horns
- colpocephaly: which can give a “teardrop” configuration on axial scans
septum pellucidum: absent
interhemispheric fissures: widened
gyri: may be seen in a “sunray appearance” on the sagittal plane
colour Doppler study may show an abnormal course of pericallosal arteries
5
Q
Dysgenesis of the corpus callosum: Prognosis
A
Variable depending on the presence of other abnormalities
6
Q
Dysgenesis of the corpus callosum: Differential diagnosis
A
Ddx of an interhemispheric cyst
Cavum septum pellucidum
Cavum vergae
cavum velum interpositum
interhemispheric arachnoid cyst
7
Q
Dysgenesis of the corpus callosum: radiographic features - MRI
A
ventricles
- run parallel rather than the normal “bow-tie” configuration giving a racing car appearance on axial imaging
- colpocephaly (dilatation of the trigones and occipital horns) gives a characteristic “Texas longhorn”/moose head/viking helmet appearance on coronal imaging
- dilated high-riding 3rd ventricle appears to communicate with the interhemispheric cistern or project superiorly as a dorsal cyst
cortex
- bundles of Probst
- radial gyri (absent cingulate gyrus)
- everted cingulate gyrus
limbic system
- hypoplastic fornices
- hypoplastic hippocampi
8
Q
Chiari 1 Malformation: Definition
A
Most common variant. Caudal descent of the cerebellar tonsils through the foramen magnum
9
Q
Chiari 1 Malformation: Epidemiology
A
0.5-3.5% of the general population
F >M = 3:1
10
Q
Chiari 1 Malformation: Clinical Presentation
A
- Occipital headache
- Exacerbated by cough, Valsalva, neck extension, or physical exertion
- Less common: Cerebellar, brainstem, bulbar, cord motor/sensory symptoms
- Cerebellar symptoms: Ataxia, dysarthria, oscillopsia, nystagmus
- Brainstem & Bulbar symptoms: Vertigo, diplopia, dysphagia, aspiration, apnea, syncope, bradycardia, sudden death (rare)
- Spinal cord dysfunction: Motor & sensory losses, hyporeflexia, hyperreflexia, clonus, gait disturbance, neuropathic joint, urinary incontinence, positive Babinski sign, scoliosis
- 15-30% of adults with CM1 are asymptomatic, up to 35% of children with 5-10 mm of tonsillar herniation are asymptomatic
- Not much difference in clinical symptoms between complex Chiari & typical Chiari 1
11
Q
Chiari 1 Malformation: Associations
A
- cervical cord syrinx in ~35% (range 20-56%): more common in symptomatic patients
-
hydrocephalus in up to 30% 2,3 of cases
- thought to result from abnormal CSF flow dynamics through the central canal of the cord and around the medulla
- skeletal anomalies in ~35% (range 23-45%) 2,3:
12
Q
Chiari 1 Malformation: Diagnostic clue
A
Pointed cerebellar tonsils (unilateral or bilateral) extending ≥ 5 mm below foramen magnum (basion-opisthion line, a.k.a. McRae line)
- Mild variations in measurement reported in literature; measurement on its own may not be definitive of diagnosis
- No consensus statement on exact definition
13
Q
Chiari 1: CT
A
- Crowding of foramen magnum on axial CT images
- Sagittal reconstructed images are very helpful
- Partially imaged superior aspect of spinal cord syrinx may be identified
- Associated osseous anomalies may include small posterior fossa, short horizontal clivus, retroverted dens, basilar invagination, platybasia, hypoplastic occipital condyles, segmentation anomalies (such as atlantooccipital assimilation), scoliosis
14
Q
Chiari 1 Malformation: MRI
A
- T1WI, T2WI, FLAIR
- Pointed (not rounded) cerebellar tonsils extending ≥ 5 mm below foramen magnum
- Crowded foramen magnum with small/effaced cisterns ± brainstem compression (kinking)
- ± small posterior fossa, elongated 4th ventricle
- ± syringohydromyelia/syrinx, scoliosis
- Syrinx reported in 30-70% of cases
- Patients with syrinx more likely to have scoliotic curve > 20⁰ (~ 70%) than those without syrinx (~ 45%)
- Other descriptions usually considered subtypes
- Chiari 1.5: Brainstem herniation
- Obex located below foramen magnum
- Complex Chiari: Medullary kink, retroflexed dens, abnormal clival-cervical angle, atlantooccipital assimilation, basilar invagination, platybasia
- Chiari 1.5: Brainstem herniation
- MR cine
- Restricted CSF flow through foramen magnum ± increased brainstem/cerebellar tonsil motion (pistoning)
- Clinical utility of this sequence debatable
- Restricted CSF flow through foramen magnum ± increased brainstem/cerebellar tonsil motion (pistoning)
15
Q
Chiari 1 Malformation: Treatment
A
- Posterior fossa decompression: Suboccipital craniectomy with C1 laminectomy ± duraplasty, arachnoid opening/dissection, cerebellar tonsil cautery/resection
- Decrease of syrinx size in majority of patients after decompression
- Complex Chiari 1 may also require odontoid resection or CCJ fusion
- Scoliosis may improve from decompression alone but often requires bracing or additional surgery
- Postoperative complications in ~ 20% of adults & 37% of children
- Most common: CSF leak, pseudomeningocele, infection
- Increased risk with duraplasty
- 1-11% postoperative mortality
- Most common: CSF leak, pseudomeningocele, infection
- Conservative management for asymptomatic or minimally symptomatic children without syrinx
16
Q
Chiari II: Definition
A
Chiari 2 malformation: Constellation of intracranial anomalies, mainly hindbrain herniation, in setting of open spinal dysraphism [either myelomeningocele (MMC) or myelocele/myeloschisis
17
Q
Chiari II: Epidemiology
A
M = F
0.44/1000
Decreased risk with folate therapy
18
Q
Chiari II: Clinical presentation
A
- ### Most common signs/symptoms
- 80-90% develop hydrocephalus requiring shunting, though less incidence of shunting in those who undergo prenatal repair of the open spinal dysraphism
- Varying degrees of lower extremity paresis/spasticity, clubfoot, bowel/bladder dysfunction
- ± epilepsy, symptoms from brainstem compression (swallowing difficulties, stridor, apnea)
- Laboratory
- Fetal screening: ↑ alpha-fetoprotein
*
- Fetal screening: ↑ alpha-fetoprotein
19
Q
Chiari II: radiological features - diagnostic clue
A
- ### Best diagnostic clue
- Small posterior fossa with inferior cerebellar and brainstem herniation in presence of open spinal dysraphism
- ### Location
- Intracranial (supratentorial + infratentorial) and intraspinal neuroectoderm + surrounding mesoderm (skull, spine)
- ### Morphology
- Grading system for Chari II malformation on fetal MR based on posterior fossa morphology
- Grade 1: 4th ventricle and cisterna magna are patent
- Grade 2: 4th ventricle is effaced, cisterna magna is patent
- Grade 3: 4th ventricle and cisterna magna are effaced
- Grading system for Chari II malformation on fetal MR based on posterior fossa morphology
20
Q
Chiari II: radiological features - CT
A
- ### Bone CT
- Small posterior fossa with bony deformities from pressure of cerebellum and brainstem
- Large foramen magnum with notched opisthion
- Posterior concavity/scalloping of clivus and petrous temporal bones
- Low-lying tentorium/torcular Herophili inserts near foramen magnum
- Small posterior fossa with bony deformities from pressure of cerebellum and brainstem
21
Q
Chiari II: radiological features - MRI
A
- Hindbrain herniation (postnatal repair)
- Caudal descent of pointed tonsils/vermis into foramen magnum
- Towering appearance of cerebellum with upward herniation through widened incisura
- Cerebellar hemispheres wrap around brainstem
- Elongated, effaced, inferiorly displaced 4th ventricle with flattened fastigium
- Cerebellar atrophy over time; most severe form: Vanishing cerebellum
- Significant hindbrain herniation is not usually present in setting of prenatal repair
- Small posterior fossa with downward-sloping tentorium, low torcular Herophili
- Tectal beaking, brainstem caudal displacement ± cervicomedullary kink
- ± ventriculomegaly
- Midline anomalies: Large massa intermedia, callosal hypogenesis/dysgenesis, absent septum pellucidum
- ± neuronal migrational anomalies: Heterotopia, polymicrogyria, rhombencephalosynapsis
- Falx insufficiency with interdigitation of hemispheric gyri
- Stenogyria (elongated, compact gyri) after shunting (differs from polymicrogyria)
- Significant hindbrain herniation not always present on fetal MR in setting of open spinal dysraphism (~ 8%)
22
Q
Chiari II: radiological features -USS
A
- ### Grayscale ultrasound
- Prenatal US key for early diagnosis
- Nearly all cases can be identified in 2nd trimester
- Lemon sign: Bifrontal concavity of calvarium
- Banana sign: Cerebellum wraps around brainstem
- Postnatal head US
- Findings follow MR, though posterior fossa more difficult to visualize due to distance from transducer
- Mastoid fontanelle view may be helpful for posterior fossa visualization
- Useful for following change in ventricular size to know if CSF diversion (shunting) required
- Findings follow MR, though posterior fossa more difficult to visualize due to distance from transducer
- Prenatal US key for early diagnosis
23
Q
Chiari II: treatment
A
- Folate supplement for pregnant mothers (preconception → 6 weeks postconception) significantly decreases MMC risk
- Surgical management
- MMC classically repaired in first 48 hours after delivery
- Early intervention required to reduce risk of infection
- Many different techniques described: Primary skin closure, myocutaneous flap, fasciocutaneous flap
- CSF diversion/shunting ultimately required in 80-90%
- Required in majority of patients (~ 60% in neonatal period); 10-20% do not develop hydrocephalus
- Posterior fossa decompression in those who do not improve with shunting
- There has been shift away from this practice in recent years
- MMC classically repaired in first 48 hours after delivery
- Fetal MMC repair in select patients
- Must have hindbrain herniation and upper level of spinal defect T1-S1
- Reduces need for shunting; may improve neurologic outcomes in some patients
24
Q
Arachnoid cyst: Terminology
A
Intraarachnoid CSF-containing sac that does not communicate with ventricular system
25
Arachnoid cyst: epidemiology
* 75% in children
* M:F = 3-5:1
* Most common intracranial cystic abnormality
* 1% of all intracranial masses
* 2% incidental finding on imaging for seizure
26
Arachnoid cyst: treatment
* Usually none
* Majority of ACs are found incidentally
* Resection (may be endoscopic)
* Fenestration/marsupialization
* Shunt (cystoperitoneal is common option)
27
Arachnoid cyst: differentials
* ## [Epidermoid Cyst](https://app.statdx.com/document/epidermoid-cyst/704c5ddf-e1f7-4a5d-a1b8-5b0e603170d9)
* Scalloped margins
* Insinuating growth pattern
* Creeps along into CSF cisterns
* Surrounds, engulfs vessels/nerves
* ACs displace but usually do not engulf vessels, cranial nerves
* Does not suppress on FLAIR
* Restricted diffusion (bright) on DWI
* ## [Chronic Subdural Hematoma](https://app.statdx.com/document/chronic-subdural-hematoma/cc7b52b4-c6a0-4b4e-ae8c-f05bfc5c5cb2)
* Signal not identical to CSF
* Often bilateral, lentiform-shaped
* ± enhancing membrane
* Look for foci of blooming on T2\*
* \< 5% of ACs hemorrhage
* ## Subdural Hygroma
* Often bilateral
* Crescentic or flat configuration
* ## Other Nonneoplastic Cysts
* Porencephalic cyst
* Surrounded by gliotic brain, not compressed cortex
* History of trauma, stroke common
* Neurenteric cyst
* Rare; spine, posterior fossa = most common locations
* Often proteinaceous fluid
* Neuroglial (glioependymal) cyst
* Rare
* Usually intraaxial
28
Arachnoid cyst: Radiology features - diagnostic clues
* ### Best diagnostic clue
* Sharply demarcated, round/ovoid extraaxial cyst that follows CSF attenuation/signal
* ### Location
* Middle cranial fossa (MCF) (50-60%)
* Cerebellopontine angle (CPA) (10%)
* Suprasellar arachnoid cyst (SSAC), variable types (10%)
* Noncommunicating = cyst of membrane of Liliequist
* Communicating = cystic dilation of interpeduncular cistern
* Miscellaneous (10%)
* Cerebral convexity
* Quadrigeminal plate
* Retrocerebellar
* ### Size
* Varies from few mm to 5 cm or more
* ### Morphology
* Sharply delineated, translucent cyst
* Displays features of extraaxial mass
* Displaces cortex
* "Buckles" gray-white interface
29
Arachnoid cyst: Radiology features - CT
* ### NECT
* Usually CSF density
* Hyperdense if intracyst hemorrhage present (rare)
* May expand, thin/remodel bone
* ### CECT
* Does not enhance
* ### CTA
* Posterior displacement of middle cerebral artery (MCA) in MCF ACs
* Cisternography may demonstrate communication with subarachnoid space
30
Arachnoid cyst: Radiology features - MRI
* ### T1WI
* Sharply marginated extraaxial fluid collection isointense with CSF
* ### T2WI
* Isointense with CSF
* ### PD/intermediate
* Isointense with CSF
* ### FLAIR
* Suppresses completely
* ### T2\* GRE
* No blooming unless hemorrhage present (rare)
* SWI can demonstrate veins displaced around AC
* ### DWI
* No restriction; nearly identical to ventricles
* ### T1WI C+
* Does not enhance
* ### MRA
* Cortical vessels displaced away from calvarium
* ### MRV
* Can demonstrate anomalies of venous drainage
* ### MRS
* Can predict pathology in \> 90% of similar-appearing intracranial cystic lesions
31
Colloid cyst: definition
Colloid cysts of the third ventricle are benign epithelial lined cysts with characteristic imaging features. Although usually asymptomatic, they can rarely present with acute and profound hydrocephalus.
32
Colloid cyst: epidemiology
Age: 3rd-4th decades, rare in children
M = F
33
Colloid cyst: Clinical presentation
* ### Most common signs/symptoms
* Headache (50-60%)
* Less common = nausea, vomiting, memory loss, altered personality, gait disturbance, visual changes
* Acute foramen of Monro obstruction may lead to rapid onset hydrocephalus, herniation, death
* 40-50% asymptomatic, discovered incidentally
* 5-15% 5-year risk of future progression necessitating operative intervention
* ### Clinical profile
* Adult with headache
34
Colloid cyst: Treatment
* Most common = complete surgical resection
* Neuronavigation-guided endoscopic removal + capsule coagulation
* 50% experience short-term memory disturbance (usually resolves)
* Recurrence rare if resection complete
* Options
* Stereotactic aspiration (difficult with extremely viscous/solid cysts)
* Imaging features that may predict difficulty with percutaneous therapy
* Hyperdensity on CT/hypointensity on T2WI suggest high viscosity
* Ventricular shunting
* Observation (rare; not recommended, as sudden obstruction can occur with even small CCs)
*
35
Colloid cyst: Radiology - general features
* ### Best diagnostic clue
* Hyperdense foramen of Monro mass on NECT
* ### Location
* \> 99% are wedged into foramen of Monro
* Attached to anterosuperior 3rd ventricular roof
* Pillars of fornix straddle, drape around cyst
* Posterior part of frontal horns splayed laterally around cyst
* \< 1% found at other sites
* Lateral, 4th ventricles
* Extraventricular CCs (very rare)
* Parenchyma (cerebellum)
* Extraaxial (prepontine, meninges, olfactory groove)
* ### Size
* Variable (few mm to 3 cm)
* Mean: 15 mm
* ### Morphology
* Well-demarcated round \> ovoid/lobulated mass
*
36
Colloid cyst: Radiology - CT
* ### NECT
* Density correlates inversely with hydration state
* 2/3 hyperdense
* 1/3 iso-/hypodense
* ± hydrocephalus
* Rare
* Hypodense
* Change in density/size
* ### CECT
* Usually does not enhance
* Rim enhancement (rare)
37
Colloid cyst: Radiology - MRI
* ### T1WI
* Signal correlates with cholesterol concentration
* 2/3 hyperintense on T1WI
* 1/3 isointense
* Small CCs may be difficult to see
* May have associated ventriculomegaly
* ### T2WI
* Signal more variable
* Generally reflects water content
* Majority isointense to brain on T2WI
* Small CCs may be difficult to see
* Less common findings
* 25% mixed hypo/hyper ("black hole" effect)
* Rare
* Fluid-fluid or blood-fluid level (cyst "apoplexy"), Ca⁺⁺ rare
* ### FLAIR
* Does not suppress
* ### DWI
* Does not restrict
* ### T1WI C+
* Usually no enhancement
* Rare: May show peripheral (rim) enhancement
* ### MRS
* Normal brain metabolites absent
38
Colloid cyst: Differential diagnosis
* ## [Neurocysticercosis](https://app.statdx.com/document/neurocysticercosis/6a45835f-6d7c-443e-874a-f33131d3def1)
* Multiple lesions within parenchyma and cisterns
* Associated ependymitis or basilar meningitis common
* Ca⁺⁺ common
* Look for scolex
* ## Cerebrospinal Fluid Flow Artifact (MR "Pseudocyst")
* Multiplanar technique confirms artifact
* Look for phase artifact
* ## [Vertebrobasilar Dolichoectasia/Aneurysm](https://app.statdx.com/document/asvd-fusiform-aneurysm/883c9117-6fdb-4030-8765-aedd9711432a)
* Extreme vertebrobasilar dolichoectasia (VBD) can cause hyperdense foramen of Monro mass
* Look for flow void, phase artifact on MR
* ## Neoplasm
* [Subependymoma](https://app.statdx.com/document/subependymoma/b899ded1-d2f2-4dc4-9812-48d3fb194117)
* Frontal horn of lateral ventricle
* Attached to septum pellucidum
* Patchy/solid enhancement
* [Craniopharyngioma](https://app.statdx.com/document/craniopharyngioma/00e66680-6731-4287-b5a1-3f0b3f09053b)
* 3rd ventricle rare location
* Usually not wedged into foramen of Monro, fornix
* Ca⁺⁺, rim/nodular enhancement common
* [Pituitary adenoma](https://app.statdx.com/document/pituitary-microadenoma/283f3068-d369-4f79-bf01-0f2b82c6e49b)
* Rare in 3rd ventricle
* Enhances (usually strongly, uniformly)
* ## Choroid Plexus Mass
* [Choroid plexus papilloma](https://app.statdx.com/document/choroid-plexus-papilloma/18e712f5-8553-487d-a939-044336cbf0ad)
* Rare in 3rd ventricle
* Tumor of early childhood
* [Xanthogranuloma](https://app.statdx.com/document/choroid-plexus-cyst/1f3fc9e9-9243-4d74-8261-7db846eeac05)
* Rare in 3rd ventricle
* Ovoid \> round
* Can be hyper- or hypodense ± Ca⁺⁺
* Can obstruct foramen of Monro
* Can be indistinguishable on imaging studies
* [Choroid plexus cyst](https://app.statdx.com/document/choroid-plexus-cyst/1f3fc9e9-9243-4d74-8261-7db846eeac05)
* Usually found in infants
* Anechoic at ultrasound
39
Colloid cyst: complications
* Varies with presence/rate of growth, development of cerebrospinal fluid (CSF) obstruction
* Colloid Cyst Risk Score (CCRS)
* 5-point measure to predict symptomatic clinical status, stratify risk for hydrocephalus
* Age \< 65 years; headache, cyst ≥ 7 mm, FLAIR hyperintense, anatomic risk zone (I-III from front to back of 3rd ventricle)
* CCRSs 2 to 5 = 13% → 100% symptomatic, 8% → 83% develop hydrocephalus
* Prognosis excellent when CCs diagnosed early and excised
* 90% stable or stop enlarging
* Older age
* Small cyst
* No hydrocephalus
* Hyperdense on NECT, hypointense on T2-weighted MR
* 10% enlarge
* Younger patients
* Larger cyst, hydrocephalus
* Iso-/hypodense on NECT, often hyperintense on T2WI
* May enlarge rapidly, cause coma/death
* Rare: Hemorrhage with cyst "apoplexy"
* Rare: Regression
