mnemonics Flashcards

Question

Expansile lytic rib lesion FAMEB

Answer 1

FD ABC Mets, myleoma, Plasmacytoma Enchondroma Brown tumour

Answer 2

Osteonecrosis of the navicular

Answer 3

AVN of the 2nd MT head

Answer 4

more common in medial meniscus absent bow tie sign if fragment flips anteriorly = double delta sign (either meniscus) if fragment flips posterior = double PCL sign (medial meniscus only)

Answer 5

more common laterally

Answer 6

benign hyperplastic proliferation of the synovium within the joint

Answer 7

SemiMembranousus and Medial head of gastrocnemius Baker's M&M

Answer 8

Inferomedial neck lateral femoral diaphyseal and transverse diaphyseal fractures.

Answer 9

fracture of the pars interarticularis - leads to spondylolisthesis

Answer 10

<12 mm < 2.5 mm in adults < 5 mm in children

Answer 11

Superior labrum anterior posterior tear - centered at the attachement of the bicepos tendon - anterior-posterior of the superior labrum Glenoid labral articular disruption - superficial tear of the anterior-inferior labrum

Answer 12

Both supraspinatus and infraspinatus infraspinatus muscle only

Answer 13

1) radial head fracture and tearing of the interosseous membrane with ulnar dislocation at the distal radioulnar joint. 2) Mid diaphyseal ulnar fracture and radial head dislocation 3) radial diaphyseal fracture and distal ulnar dislocation,

Answer 14

AVN of the lunate

Answer 15

1:3000 autosomal dominant Cafe au lait spots axillary or inguinal freckling fibromas - (neurofibroma) plexiform eye harmartoma - lisch nodules - pigmented nodules of the iris skeletal abnormalities - sphenoid wing dysplasia postive family history optic tumour - gliomas of the optic nerve peripheral nerve sheath tumour - plexiform neurofibroma pheochromocytoma sphenoid wing dysplasia, posterior vertebral scalloping, rib notching, tibial bowing Brain neoplasms - Optic nerve glioma juvenile pilocytic astrocytoma brainstem glioma Also associated with multiple extra-cranial neoplasms Wilms tumour, Rhabdomyosarcoma, AML, leiomyosarcoma

Answer 16

Multiple inherited schwannomas meningioma ependymoma

Answer 17

pleuropulmonary blastoma - 3 types - cystic, mixed cystic solid and purely solid Inflammatory myofibroblastic tumour Mesenchymal hamartoma -

Answer 18

Pit para panc pituitary adenoma parathyroid proliferative disease pancreatic endocrine tumours

Answer 19

PMP Pheochromocytoma Medullary thyroid ca Parathyroid hyperplasia

Answer 20

PMMM Pheochromocytoma Medullary thyroid ca Mucosal neuroma Marfinoid habitus

Answer 21

MEN syndrome Cardiac myxoma Skin pigmentation

Answer 22

3 tumours Extra-adrenal paraganglioma GIST Pulmonary chondroma

Answer 23

medullary MR -Variable T1/T2 signal due to hemorrhage, cystic degeneration, and necrosis Traditional classic imaging feature: T2 ("light bulb") hyperintensity Hypervascular solid components assoc autosomal dominant familial syndromes von Hippel-Lindau, multiple endocrine neoplasia 2, neurofibromatosis type 1 Classic teaching: Rule of 10s (or 10% tumor) 10% extraadrenal (paraganglioma) 10% bilateral 10% malignant 10% extraabdominal 10% familial 10% pediatric 10% silent 10% autosomal dominant transmission DDX - adrenal adenoma adrenal carcinoma adrenal mets and lymphoma

Answer 24

aggressive permeative lesion in diaphysis of a child second most common malignant primary bone tumors of childhood after osteosarcoma, typically arising from the medullary cavity with the invasion of the Haversian system. Ewing sarcomas usually present as moth-eaten, destructive, and permeative lucent lesions in the shaft of long bones, with a large soft tissue component and typical onion skin periostitis. These tumors may also involve flat bones and can appear sclerotic in up to 30% of cases.

Answer 25

Wilms tumor, also known as nephroblastoma, is a malignant pediatric renal tumor.

Answer 26

Lack of oxidation of long chain fatty acids that results in a severe inflammatory demyelination spares subcortical u-fibres Involves symmetric occipital white matter and splenium of corpus callosum

Answer 27

autosomal recessive lysosomal storage disorder white matter diffusely affected Bilateral symmetric periventricular change - butterfly pattern spares u-fibres

Answer 28

Rosenthal fibres Involves subcortical u-fibres, basal ganglia and enhances involves frontal white matter Starts in frontal region and extends posteriorly. Involves u-fibers early in disease

Answer 29

Prevelant in Jewish Autosomal recessive due to gene mutation leading to deficiency of N-acetylasparta and accumulation of NAA in brain, CSF and plasma and urine Bilateral diffuse symmetrical white matter involvement involves subcortical u-fibres, basal ganglia, thalamus Spares CC, caudate and internal capsule No enhancment diffuse white matter involvement

Answer 30

Tetralogy of fallot transposition of the great arteries - 90% NOT associated with a syndrome. Common in diabetic mother truncus arteriosus total anomalous pulmonary venous return (TAPVR - pulmonary and systemic veins all drain into the right atrium) tricuspid valve abnormalities

Answer 31

TGA TOF - VSD, Obstruction of right ventricle outflow, aorta overides VSD, right ventricular hypertrophy TAPVR Co-arctation Ebstein

Answer 32

Temporal arteritis Takayasu - granulomatous vasculitis of medium + large art (aortic arch) Polyarteritis nodosa - kidneys (spares lungs) p-ANCA Kawasaki - Self-limited small and medium vessel vasculitis in young children that can lead to coronary artery aneurysms Churg-Strauss syndrome - small vessel necrotizing vasculitis in patients with asthma and eosinophilia - ANCA + 40% Bechet - small to medium neutrophilic vasculitis - Chronic, idiopathic, relapsing-remitting, multisystem vascular-inflammatory disease characterized by recurrent orogenital ulcerations and uveitis

Answer 33

ASD - 90% secundum VSD - 90% in membranous intraventricular septum PDA

Answer 34

osteochondroma that points towards the joint

Answer 35

Renal osteodystrophy hyperparathyroidism Pagets ostepetrosis

Answer 36

Hyperparathyroid Multiple myeloma

Answer 37

Atherosclerosis NF1 - ostium FMD - distal artery vasculitis

Answer 38

TSC1 and TSC2 cortical and subcortical tubers SEGA Renal AML Cardiac rhabdomyomas LAM - rare

Answer 39

Numerous benign and malignant tumours RCC Pheochromocytoma Pancreatic cysts CNS - hemangioblastoma

Answer 40

Thymoma Teratoma Thyroid Terrible lymphoma Thoracic aorta

Answer 41

Vertebral anomalies Anal atresia Cardiovascular anomalies Tracheo-esophageal fistula Renal/radial anomalies Limb defects

Answer 42

Leukaemia Infection (TORCH) Neuroblastoma mets Endocrine - Ricket's ,scurvy

Answer 43

FD Enchondroma GCT NOF Osteoblastoma Mets/myeloma ABC SBC Hyperparathyroidism (brown tumour) Infection Chondroblastoma or chondromyxoid fibroma

Answer 44

Cancer - squamous Autoimmune (wegners, rheum) Vascular - septic emboli Infection - TB Trauma - pneumatocele Young - Congenital (CCAM, sequestration)

Answer 45

Melanoma Renal carcinoid/cholangioncarcinoma thyroid

Answer 46

Pleomorphic xanthroastrocytoma DNET - dysembryonic neuroepithelial tumour Oligodendroglioma ganglioglioma

Answer 47

toxoplasmosis Other - syphilis, varicella, parvovirus B19 Rubella CMV HSV

Answer 48

Amyloid RA (cystic) Reticular histocytosis Sarcoid Hyperlipidaemia

Answer 49

Hyperparathyroidism Acidosis - renal tubular Medullary sponge kidney Hypercalacaemia Oxalosis Papillary necrosis

Answer 50

Chraniopharyngioma Astrocytoma, aneurysm Choroid plexus tumour oligodendroglioma Meningioma Ependymoma

Answer 51

Mets abscess glioma infarct contusion demyelination radiation

Answer 52

Glioma - brainstem Astrocytoma - pilocytic medulloblastoma ependymoma

Answer 53

Schwannoma - enhance Arachnoid cyst Meningioma - enchance Epidermoid cyst - RD

Answer 54

Sarcoidosis Adenoma/aneurysm Teratoma/germinoma, TB Chraniopharyngioma, Ranthke's Cleft cyst Hypothalamic hamartoma, histiocytosis Meningioma, mets Optic pathway glioma

Answer 55

Pyelonephritis (infection) Obstruction Sickle cell disease TB Cirrhosis Analgesic abuse renal vein thrombosis DM Systemic vasculitis

Answer 56

Malignancy Myelofibrosis Mastocytosis Sickle cell disease Pagets Renal osteodystrophy Osteopetrosis Other Fluorosis

Answer 57

looks like mets - single or multiple masses is a type of lymphoma caused by ebstein barr virus after solid organ or BM transplant. renal transplant patients most at risk.

Answer 58

Cortical necrosis (acute) Oxaluria (hyper) Alport syndrome (chronic) glomerulonephritis

Answer 59

AML Malignant neoplasm renal calculus intrarenal gas milk of calcium sloughed papilla

Answer 60

Normal PSV = 60 - 100 cm/sec >125 cm/sec >50% stenosis >230 cm/sec >70% stenosis Waveform - before the stenosis will be high resistance with spectral broadening After stenosis - low resistance with tardus parvus waveform

Answer 61

HYPOthyroid increased right of thyroid lymphoma diffusely nodular or coarsened gland on USS HYPERthyroid thyrotoxicosis enlarged gland with coarse echotexture thyroid inferno - increased blood flow

Answer 62

viral gland is tender with adjacent cervical adenopathy heterogenous gland with patchy areas of decreased echogenicity

Answer 63

complete lack of brain above the orbits protrusion of brain and meninges outside the calvarium Failure of midline cleavage - fused thalami, no falx Looksfor cavum septum pellucidum (formed together). Septo-optic dysplasia and absent CC

Answer 64

Encephalocele Renal dysplasia - echogenic kidneys Polydactyly

Answer 65

increased risk of Wilms tumour\ hemihypertrophy, organomegaly macroglossia omphalocele perinatal hypoglycaemia

Answer 66

cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy Hereditary small-vessel disease due to mutations in NOTCH3 gene on chromosome 19, which causes stroke in young to middle-aged adults FINDINGS: Diffuse white matter hyperintensities = leukoaraiosis, early finding Multiple lacunar infarcts Anterior temporal pole, external capsule, and paramedian superior frontal lobe highly sensitive and specific locations Diffusion restriction in acute lacunar infarcts

Answer 67

Recommend In-111 octreotide scan / I-123 labelled MIBG scan. Correlate with chromogranin A and 5HIAA levels 5-HIAA (5-hydroxyindoleacetic acid): usually suggests a functioning carcinoid tumor chromogranin A (CgA): considered a valuable tool in the diagnosis of neuroendocrine neoplasia in general

Answer 68

Caplan syndrome, also known as rheumatoid pneumoconiosis, is the combination of seropositive rheumatoid arthritis and a characteristic pattern of fibrosis.

Answer 69

Coloboma Heart anomaly Atresia choanae Restricted growth and development: Mental and somatic development Genital hypoplasia Ear abnormalities

Answer 70

primary malignant tumour arising from either the visceral or parietal pleura 1000x increased risk in asbestos workers 80% are asbestos related Smoking has NO association or synergistic effect 3 types Epithelial type (60%) Sarcomartoid type (20%) - worst prognosis Mixed type

Answer 71

Mycobacterium tuberculosis caseating granulomatous inflammation Type IV hypersensitivity reaction: cell mediated immunity (by T helper lymphocytes) PRIMARY TB - Ghon complex - 1cm subpleural lesion in midzone with caseous centre (Ghon focus) + ipsilateral caseous tracheobronchial nodes SECONDARY (reactivation) TB PROGRESSIVE TB subtypes - cavitatory, miliary, tb bronchopneumonia, empyema

Answer 72

immunologically mediated mixed alveolar and predominently interstitial lung disorders caused by prolonged exposure to inhaled organic dusts acting as antigen.

Answer 73

Non caseating granulomas

Answer 74

Wegener's granulomatosis. C-ANCA Churg-Strauss syndrome P-ANCA Systemic Lupus Erythematosus (SLE)

Answer 75

Rare disease of unknown aetiology characterised by airspace consolidation due to accumulation of an amorphous protein - lipid (PAS positive) granular precipitate within alveoli

Answer 76

Scleroderma SLE RA

Answer 77

aspirin and beta agonists methotraxate and nitrofurantoin bleomycin and amiodarone

Answer 78

Burkitt's lymophoma Nasopharyngeal carcinoma Other B-cell lymohomas HCC Cervical ca and other skin ca T-cell leukaemia/lymphoma

Answer 79

HCC and germ cell Trophoblastic tumour prostatic carcinoma GI tract neoplasia Endocrine tumour

Answer 80

KaT - kaposi is Thallium avid TuG - TB is gallium avid Lymphoma likes both (thallium and gallium)

Answer 81

group of lysosomal disorders including Hurler's, Morquio and Hunters imaging findings: ant vertebral body beaking, thickened ribs and undertubulated bones Madelung deformity of the wrist thickened calvarium with J-shaped sella Hurler's - ant beaking of vertebral bodies, primarily inferiorly Morquio - middle of vertebral body ;.

Answer 82

Treponema Pallidum Wimberger sign - destructive erosion at the medial aspect of the proximal tibia symmetric periosteal reaction in a child

Answer 83

alpha angle < 60 degrees and < 50% coverage of the femoral head.

Answer 84

osteochondrosis of the proximal tibia metaphysis causing tibia varus and internal rotation which leads to progressive deformity, gair deviations and leg lenght discrepancy (sloping of the medial portions of the proximal tibia metaphysis)

Answer 85

osteochondrosis of the capitellum

Answer 86

physiological 1-4 months - lateral or medial aspect of long bones prostoglandin therapy - infectious neoplastic trauma metabolic - ricket's, scurvy syndromic - Caffey disease (infantile cortical hyperostosis) rare inflammatory disease causing periostitis of the mandible, scapula and clavicle

Answer 87

causes in utero infection in utero ischaemia genetic

Answer 88

absent or decreased cortical convolutions causing smooth, thickened cortical surface

Answer 89

full thickness cleft of the cerebal hemisphere lined by dysplastic grey matter associated with septo-optic dysplasia which is characterised by agenesis of the septum pellucidum and optic never hypoplasia

Answer 90

forebrain does not divide into two hemispheres Alobar, semilobar and lobar

Answer 91

displacement of the cerebellar tonsils beyond the foramen magnum syrinx

Answer 92

herniation of the vermis, cerebelalr tonsils, and medulla into the foramen magnum with resultant beaking of the tectum

Answer 93

enlarged posterior fossa

Answer 94

Vascular disorder facial port wine stain ocular abnormalities failure of normal cortical venous development underlying vascular anomaly leads to chronic ischaemia, cortical atrophy, and cortical calcification

Answer 95

midbrain malformation molar tooth Autosomal recessive genetic disorders with impaired ciliary function molar tooth sign on MR, intellectual impairment, hypotonia

Answer 96

Hurler syndrome Infection Trauma Dyschondrosteosis Osteochondroma Congenital - Turners

Answer 97

Mets (osteoblastic) - breast and prostate Pagets Haemangioma Infection - TB spondylitis Lymphoma (hodgkins)

Answer 98

Eosinophilic granuloma (LCH) Fibrosarcoma Infection (Brodie's abscess) Lymphoma Mets - breast ca

Answer 99

PORK CHOP Pyknodysostosis Osteogenesis imperfecta Rickets Kinky hair syndrome Cleidocranial dysostosis Hypothyroidism/Hypophosphatasia One too many chromosomes (21) downs Primary acro-osteolysis (Hadju-Cheney)

Answer 100

P - posterior fossa (dandy walker) H - Hemangiomas A - arterial anomalies C- coarctation of aorta and cardiac defects E - eye abnormalities S - subglottic hemangiomas

Answer 101

most common mass in the masticator space of a kid! extra-occular orbital malignancy - painless proptosis and no signs of infection

Answer 102

lateral - think - 2nd branchial cleft cyst lymphatic malformation - septa enhance vascular malformation (phleboliths) - cystic spaces enhance

Answer 103

ABC Osteosarcoma Osteoblastoma Osteochondroma chondromsarcoma osteoid osteoma ewings

Answer 104

Glomus tympanicum paraganglioma arises from glomus bodies situated on the cochlear promontory. Larger lesions may cause erosion of the walls of the middle ear or ossicles. As with other paragangliomas, intense enhancement is the rule.

Answer 105

Most subdural effusions occur after meningitis and are more common in children than adults. They consist of a plasma exudate, NOT cerebrospinal fluid, and do NOT contain blood. They don't enhance nor do they restrict on DWI. This distinguishes them clearly from other subdural collections such as chronic hematomas, empyemas, and hygromas

Answer 106

Wegener granulomatosis (granulomatosis with polyangiitis, GPA) involves the sinonasal cavities in over 75% of patients. Orbital extension of sinonasal disease is a characteristic feature of GPA. Because GPA is a systemic necrotizing vasculitis, the majority of patients have involvement beyond the upper respiratory tract, including the lower respiratory tract, kidneys, skin, and joints. Sarcoidosis is an idiopathic granulomatous inflammatory disease that involves the sinonasal cavities in about 20% of patients. Nasal septal perforation is a characteristic feature and does not imply secondary malignancy. Both GPA and sarcoidosis have a similar imaging appearance, with a predilection for the nasal cavity, production of nodular soft tissue lesions, bone destruction, and nasal septal perforation

Answer 107

Low-grade diffusely infiltrating astrocytoma does not enhance. Infection (e.g., ventriculitis) and neoplasm (e.g., medulloblastoma and ependymoma in children, lymphoma and glioblastoma multiforme in adults) can both cause ependymal enhancement. Much of the cerebral white matter of the corona radiata drains centrally into subependymal veins. These normally enhance with contrast and should not be mistaken for pathology. Normal enhancing subependymal veins are usually thin and linear, not fat and nodular. A "rind" of ependymal thickening and enhancement is not a normal finding.

Answer 108

Fibromuscular dysplasia (FMD) is an arteriopathy of unknown etiology that affects medium and large arteries. The carotid arteries are involved in about a 3rd of all cases, with the vertebral artery involved in about 10%. Bilateral carotid artery lesions are found in about 2/3 of all cases. The "string of beads" appearance is most common (85% of cases) and is caused by medial fibroplasia. Long tubular stenosis is caused by intimal fibroplasia and accounts for 10% of cephalocervical FMD cases. A rare variant is periadventitial fibroplasia, where there is an asymmetric outpouching that involves 1 side of the artery. FMD carries increased risk of vascular complications including dissection, transient ischemic attacks, and subarachnoid hemorrhage from saccular aneurysm.

Answer 109

A small cyst in the right paraglottic space is consistent with an internal laryngocele secondary to an enhancing glottic squamous cell carcinoma (SCCa) with nodularity anteriorly (Fig. 2). The term secondary laryngocele is used when a glottic level lesion obstructs the laryngeal ventricle and creates a laryngocele superiorly. Laryngopyocele shows inflammatory findings of a thickened wall and inflammatory stranding in surrounding soft tissues. Thyroglossal duct cyst may extend into the preepiglottic space in the anterior midline but not in the more lateral paraglottic space. This is not a hypopharyngeal diverticulum, as it does not communicate with the hypopharyngeal airway.

Answer 110

Remember the larynx can be divided into 3 major pieces, the supraglottis, glottis and, subglottis. The supraglottic larynx is further divided into three subsites, the epiglottis, aryepiglottic folds, and the false cords.

Answer 111

The glossopharyngeal nerve (CN9) exits the skull base through the pars nervosa (along with the inferior petrosal sinus). The vagus and accessory nerves (10 and 11) exit through the pars vascularis of the jugular foramen. The hypoglossal nerve (12) exits through the hypoglossal canal , which lies just under the jugular tubercle

Answer 112

Heterotopic gray matter has a spectrum of appearances. Most commonly seen as subependymal nodules, it can also appear as bands of gray matter signal deep to the cortex ("band heterotopia") or as a nodule in a subcortical location, often adjacent to abnormal sulcation/gyration. It is important to recognize it as a cause of seizures and not to mistake it for a neoplasm.

Answer 113

Sagittal STIR MR image of the spine demonstrates Romanus lesions . Romanus lesions consist of edema and less often seen erosions involving the anterior edges of the vertebral endplates. These lesions occur at the site of attachment of the annulus fibrosus to the vertebral endplate. Such a junction of bone and ligamentous structure is an enthesis and, therefore, a Romanus lesion or spondylitis can be regarded as an enthesitis. Chronically, these lesions can sclerose, giving the classical plain film appearance of "shiny corners".

Answer 114

Spinal lipoma is intimately associated with the dorsal spinal cord (intradural) or distal cord/filum insertion (terminal). It is a hyperintense (T1WI) intradural mass. Use frequency selective fat suppression if unsure of the composition of the hyperintense mass.

Answer 115

Germ cell tumors are the most common pineal gland tumor, and germinomas are the most common type of germ cell tumor. Synchronous occurrence in the pineal gland and suprasellar cistern is a classic presentation with the suprasellar component representing a "drop metastasis" from the pineal germinoma. An adolescent male presenting with a solid tumor in both locations is pathognomonic of this type of tumor.

Answer 116

A well-demarcated lobular mass extending from the conus is typical appearance of myxopapillary ependymoma. Lack of dural attachment excludes meningioma as a possible diagnosis. Lack of multiplicity makes intradural metastases less likely, but a solitary metastases is possible. Cauda equina schwannoma may be indistinguishable from a small ependymoma, as in this case.

Answer 117

The constellation of findings seen in Sturge-Weber syndrome (also known as encephalotrigeminal angiomatosis) is due to a failed development of normal cortical veins. The brain findings are a manifestation of the resulting chronic venous ischemia, while the pial angiomatosis, facial port-wine stain (a capillary malformation classically in the trigeminal nerve first branch distribution), globe choroidal angioma, and choroid plexus enlargement are all due to attempted collateral drainage pathways. Buphthalmos ("ox eye") is enlargement of the globe that develops in patients less than 3 years of age due to increased intraocular pressure; in these patients it is likely related to impaired aqueous humor drainage due to the choroidal angioma. Bilateral intracranial involvement is seen in up to 20% of cases. Clinical manifestations are typically related to seizures, hemiplegia, mental retardation, and cosmetic issues from the port-wine stain. Seizures may require hemispherectomy for treatment. Laser therapy may improve cosmetic appearance.

Answer 118

Chordomas are locally aggressive tumors of notochordal origin, found along the neural axis from the sella to the coccyx. Intracranial chordomas constitute 1/3 of lesions, usually within the vicinity of the clivus. Chordomas have peak prevalence in the 4th decade but can occur at any age. This example shows classic features of a bulky destructive mass, midline location, "thumbing" of the pons, T2 hyperintensity, and heterogeneous enhancement

Answer 119

Squamous cell carcinoma (SCCa) is the most common sinonasal malignancy, 70% of which arise in the maxillary antrum. Although adenocarcinomas may originate in the paranasal sinuses, they have a predilection for the ethmoid sinuses and are rare in comparison with SCCa, accounting for < 20% of sinonasal neoplasms. Sinonasal lymphoma and melanoma are much less common than SCCa, and both have a predilection for originating in the nasal cavity rather than in the paranasal sinuses.

Answer 120

Look for the hemosiderin "cap" sign at the cranial &/or caudal margins of the lesion, which can be seen in 20-64% of cord ependymomas. A small focus of hemosiderin is seen in this case. There are 4 subtypes of intramedullary ependymomas: cellular (most common), papillary, clear cell, and tanycytic. Cellular ependymomas are more commonly cervical in location and tend to be multisegmental, as in this case. Fifty to 90% may have syrinx or polar tumoral cysts, such as the large superior cystic component seen in this case.

Answer 121

The V4 segments are entirely intracranial, extending from the foramen magnum to the junction with the basilar artery. The segment from the C1 transverse foramen to the foramen magnum is the V3 segment. V2 is the vertebral artery segment contained within the transverse foramens of C6 to C3. V1 is the most proximal vertebral artery (VA) segment, arising from the subclavian artery and extending to the transverse foramen of C6.

Answer 122

Intraaxial, bihemispheric masses which cross the corpus callosum are classically glioblastoma multiforme (GBM), lymphoma, or tumefactive multiple sclerosis. A patient's age and past medical history as well as associated features narrow the differential. For example, if the patient is young and MR shows other demyelinating lesions, think multiple sclerosis; if the patient is older and with a necrotic mass and ependymal spread, think glioblastoma; if the patient is immunosuppressed and with lymphopoietic abnormalities on labs, think lymphoma. It is important to remember that in GBM tumor cells may extend beyond the area of MR signal abnormality. Prognosis is very poor in GBM, with death in 9-12 months. Treatment includes biopsy/debulking followed by radiation and chemotherapy.

Answer 123

Pituitary macroadenoma is a sellar/suprasellar mass without a separable identifiable pituitary gland. These are > 10mm in diameter and > 4cm are called "giant" adenomas. Most pituitary adenomas enhance strongly but heterogeneously. Saccular aneurysm arises from the artery and is usually eccentric and the normal pituitary gland is visible separate from the mass. Meningioma is an extra-axial, strongly enhancing mass with the pituitary gland visible separate from the mass. In pituitary hyperplasia the gland is usually < 10mm in size.

Answer 124

The vascular supply to the spinal cord is supplied by the vertebral arteries and 10 medullary arteries that arise from segmental branches of the aorta. These medullary arteries join to form the anterior and posterior spinal arteries. Compromise to the spinal cord blood supply may result if any of the medullary arteries are obstructed or injured (during abdominal surgery, for example). The pattern of resulting neurological damage differs according to whether the supply to the posterior or anterior artery is interrupted. Loss of the posterior supply generally leads to loss of sensory functions, whereas loss of the anterior supply more often causes motor deficits.

Answer 125

Epidermoid cysts, arachnoid cysts, and racemose neurocysticercosis cysts in the subarachnoid cisterns all resemble cerebrospinal fluid (CSF) on NECT scans. Dermoid cysts are hypodense but are fat-like, not CSF-like.

Answer 126

Optic neuritis Acute optic neuritis is most common in younger adult women and typically presents with sudden vision loss. MR is the best imaging tool and shows abnormal T2 hyperintensity, as well as enhancement with minimal enlargement of the nerve.

Answer 127

The Meckel cave is largely filled with cerebrospinal fluid (CSF). The trigeminal nerve (CN5) and ganglion occupy only a small fraction of the total volume of Meckel cave. On coronal T2WIs, fascicles of the trigeminal nerve appear as dot-like filling defects in the CSF-filled ovoid structure. The trigeminal ganglion sits at the bottom of the cave and is a thin, semilunar-shaped structure that is isointense to brain.

Answer 128

Cavernous malformations are often associated with developmental venous anomaly (DVA). In fact when a cavernous malformation presents as an acute intracranial hemorrhage the presence of an associated DVA is an important clue to the diagnosis.

Answer 129

If the patient has a normal hematocrit, all dural venous sinuses normally appear slightly hyperdense compared to adjacent brain parenchyma (physiologic hyperdensity) on NECT scans. Polycythemia makes ALL the cranial vessels (dural sinuses as well as veins and arteries) appear similarly dense. Carefully examine the shape of a suspect dural venous sinus. Normally, its walls are flat or slightly concave. If they appear bulging and convex outward, a clot may be present. Contrast-enhanced CT (looking for an "empty delta" sign) or CTA/CTV usually resolves the issue. Lastly, beware the acute peritentorial subdural hematoma (SDH) that layers along the straight sinus and tentorium. A small, thin peritentorial SDH can mimic dural sinus thrombosis, but the clot is on the outside (not the inside) of the sinuses. Coronal reformatted images are very helpful in detecting peritentorial SDHs and distinguishing them from the normal, slightly hyperdense dura and venous sinuses on NECT scans.

Answer 130

Giant cell tumor (GCT) lytic, expansile lesion centered in the posterior elements can be a GCT. There is no associated soft tissue mass, marginal sclerosis, or matrix within the mass, which fits with GCT. Between 10-15% of GCTs also have an aneurysmal bone cyst component, which probably accounts for the fluid-fluid levels seen in this case. Elements of aneurysmal bone cyst (ABC) were found in the resected surgical specimen. Teaching Point Giant cell tumors (GCT) can coexist with and be indistinguishable from aneurysmal bone cysts (ABC). Histologically-mixed GCT/ABC is seen in 10-15% of cases. GCTs are locally aggressive tumors with a 12-50% recurrence rate. These lesions can undergo sarcomatous transformation, spontaneously or in response to radiation therapy. Pulmonary metastatic implants occur in 1-2% of cases. A solitary lytic, expansile vertebral body mass in a young adult that lacks a definite sclerotic margin or bony matrix is most consistent with a giant cell tumor.

Answer 131

Choroid plexus in the 4th ventricle extends anteroinferiorly through both lateral recesses and the foramina of Luschka. Choroid plexus lacks a blood-brain barrier and therefore enhances following contrast administration. The lobulated curvilinear lines of enhancement indicated by the are the choroid plexi in the lateral recesses of the 4th ventricle. Sometimes, as seen in this case, prominent tufts of enhancing choroid plexus can be seen in the lower cerebellopontine angle cisterns and should not be mistaken for pathology.

Answer 132

These are the thalamostriate veins (TSVs). The TSVs are lateral structures that run between the caudate nuclei and thalami, coursing toward the foramen of Monro. They typically unite with the septal veins, seen as faint linear hyperdensities running along the frontal horns of the lateral ventricles on this image in the midline, to form the internal cerebral veins (ICVs). The ICVs are also seen on this image as the enhancing "dots" that lie medial to the TSVs. The ICVs are seen as the tubular enhancing midline structures that course posteriorly between the thalami. The ICVs are contained in the velum interpositum, which is a cerebrospinal fluid (CSF)-filled subarachnoid space that lies just above the 3rd ventricle between the fornices.

Answer 133

The calcified level II and heterogeneously enhancing level III (Fig. 2) nodes with solid enhancing and cystic foci in the right internal jugular nodal chain are typical findings of nodal differentiated thyroid carcinoma (DTCa). This patient had undergone prior thyroidectomy with central compartment nodal dissection but presented with recurrent adenopathy. The first consideration in patients with calcified or mixed solid-enhancing and cystic nodes should be metastatic DTCa. Cystic (or necrotic) lymph nodes are encountered in both DTCa and squamous cell carcinoma (SCCa), however SCCa adenopathy is very rarely calcified. Lymphoma rarely shows nodal calcification after therapy, but the nodes are usually large and homogeneous. Reactive nodes are not calcified or inhomogeneous.

Answer 134

Acute disseminated encephalomyelitis (ADEM) is typically a monophasic illness, usually occurring after a viral infection or immunization. It is an autoimmune-mediated disorder that is generally self-limited. Enhancement varies from none to punctate, linear, or ring-like (usually incomplete, with the "open" or nonenhancing part of the ring next to the cortex). There is a fulminant, often fatal, variant of ADEM called acute hemorrhagic leukoencephalopathy (AHLE or Weston-Hurst disease) that causes multifocal brain hemorrhages that may be seen only on T2* scans (SWI is better than GRE).

Answer 135

Rathke cleft cysts (RCC) are benign, epithelium-lined intra-/suprasellar cysts that are believed to originate from remnants of the Rathke pouch. Most are incidental and asymptomatic, but patients can present with pituitary dysfunction, visual disturbances, and headaches. The most common approach in the treatment of RCC is trans-sphenoidal surgery in which the cyst is partially excised and drained.

Answer 136

A mass wedged into foramen of Monro with pillars of the fornix straddling and draped around it and the posterior part of frontal horns splayed laterally around it is characteristic of a colloid cyst. About a 3rd of colloid cysts are iso- or hypodense on NECT.

Answer 137

Medulloblastomas are rare in adults, but this case illustrates a round, dense, highly cellular mass arising in the midline within the 4th ventricle (indicated by the ), all features typical of a medulloblastoma. Atypical teratoid/rhabdoid tumor can appear very similar on imaging but is most common in very young children (< 3 years of age). Hemangioblastoma usually occurs along the pial surface of the cerebellum and often has a cyst with an enhancing mural nodule. Subependymoma frequently occurs in the 4th ventricle, often in older patients, and enhancement would be unusual.

Answer 138

Subacute subdural hematomas are typically hyperintense on T1 MR in both early and late subacute stages due to the presence of methemoglobin. Contrast-enhanced CT or MR may show enhancing membranes. The presence of enhancing membranes suggests unstable subdural hematomas that are prone to rehemorrhage. On a noncontrast CT, subacute subdural hematoma is often of the same density as the underlying cortex. Cortical vessels in the subarachnoid space are displaced medially by any subdural collection.

Answer 139

CNS cryptococcal infection takes 3 main forms: Meningitis, gelatinous pseudocysts, and focal mass lesions called cryptococcomas. Cryptococcomas and meningitis are the most common forms in immunocompetent patients, whereas meningitis and gelatinous pseudocysts are the most common forms in HIV/AIDS patients. This patient has classic gelatinous pseudocysts, seen here as multiple nonenhancing cysts in the midbrain and basal ganglia.

Answer 140

A characteristic of neurofibromatosis type 1 (NF1) is development of gliomas, especially optic pathway gliomas (OPGs). Most OPGs are pilocytic astrocytomas, a World Health Organization (WHO) grade I neoplasm. Other gliomas may develop in the posterior fossa/brainstem, basal ganglia, and cerebral hemispheres. Less than 20% of gliomas in the setting of NF1 are frankly malignant, although they do occur. There is a variant of pilocytic astrocytoma (PA) called pilomyxoid astrocytoma that is histologically and biologically more aggressive. When a lesion such as this one that looks grossly like a PA hemorrhages or grows rapidly, especially if it is in very young patients (including infants), this variant should be suspected. The histologic diagnosis in this case was pilomyxoid variant of pilocytic astrocytoma.

Answer 141

Gray matter-lined clefts are isointense to cortical gray matter on all MR sequences, although distinction of a gray matter-lined cleft can be difficult prior to myelination. "Closed-lip" schizencephaly contains an irregular tract of gray matter extending from the cortical surface to the ventricle, and the lining gray matter can appear dysplastic. "Open-lip" schizencephaly can be wide and wedge-shaped or with nearly parallel walls, and the gray matter-lined cleft may be harder to discern than in "closed-lip." Developmental delay, paresis, microcephaly, and spasticity is more common with bilateral, whereas seizures are more common with unilateral.

Answer 142

Petrous apex cholesterol granuloma Correct: T1 and T2 hyperintensity within an expansile lesion of the petrous apex is typical for cholesterol granuloma. Teaching Point The petrous apex lesion that is expansile with T1-T2 "high-high" signal is an imaging classic that tends to show up on radiology, as well as ears, nose, throat (ENT) certifying examinations.

Answer 143

Petrous apex cholesterol granuloma Correct: T1 and T2 hyperintensity within an expansile lesion of the petrous apex is typical for cholesterol granuloma. Teaching Point The petrous apex lesion that is expansile with T1-T2 "high-high" signal is an imaging classic that tends to show up on radiology, as well as ears, nose, throat (ENT) certifying examinations.

Answer 144

The large tubular enhancing structure with a "medusa head" appearance is a classic developmental venous anomaly (DVA). DVAs are often associated with cavernous malformations, and their detection is important prior to resection of cavernous malformations as they provide normal venous drainage to the surrounding tissue. GRE (Fig. 4) shows hemosiderin staining adjacent to the right aspect of the 4th ventricle, which relates to a site of old resection of a cavernous malformation.

Answer 145

Acute hypertensive encephalopathy, PRES The history and posterior circulation distribution of patchy cortical and subcortical hypodensity and MR FLAIR/T2 hyperintensity are classic for posterior reversible encephalopathy syndrome (PRES). Usually there is a supportive history, such as immunosuppressants (this case), pre-eclampsia, uremia, or drug toxicity, including recreational drugs like cocaine. PRES can almost look like anything, with a myriad of distributions (including deep gray matter), restricted diffusion, hemorrhage, and even enhancement. Keep it in the back of your differential pocket at all times. Also, remember that in children, blood pressure may be normal or only slightly elevated. Teaching Point Patchy bilateral low density foci in the occipital lobes may be the earliest manifestation of acute hypertensive encephalopathy (PRES), though it can manifest almost anywhere in the brain and have atypical features, such as ischemia on diffusion imaging or hemorrhage on gradient or susceptibility imaging. Ischemia is the major differential, but often history and distribution will support PRES.

Answer 146

Bilateral plexiform neurofibromas are present at almost every visualized spinal level with extramedullary tumors that enlarge the neural foramina. Plexiform neurofibromas are pathognomonic of neurofibromatosis type 1.

Answer 147

This patient's symptoms are suggestive of "Chiari spells" in which coughing or sneezing increases intrathecal pressure due to obstructed cerebrospinal fluid (CSF) flow and results in headaches or syncope. In Chiari 1 malformation, the cerebellar tonsils are pointed and extend >/= 5 mm below the foramen magnum . Chiari 1 malformation may be associated with syringohydromyelia, low/tethered cord; hence, imaging of the entire spine is indicated. Syringohydromyelia of the cervical cord is partially visualized on this sagittal image of the brain. Further imaging is needed as the inferior extent of the syrinx is not delineated by this brain MR alone.

Answer 148

As pars flaccida cholesteatoma enlarges, it most commonly spreads superiorly into the lateral epitympanic recess, gradually filling the superior mesotympanum and the epitympanum. As it does so, the cholesteatoma erodes the scutum and ossicles. With further enlargement, dehiscence of the lateral semicircular canal and tegmen tympani (roof of the middle ear) may be seen with or without erosion of the tympanic portion of the facial nerve canal as it passes under the lateral semicircular canal. The tympanic annulus , which is the site of attachment of the inferior margin of the tympanic membrane, is not affected by pars flaccida cholesteatoma. The pars flaccida cholesteatoma originates in the Prussak space and usually extends posteriorly, while the pars tensa cholesteatoma originates in the posterior mesotympanum and tends to extend posteromedially. Conventional non-contrast MR imaging with diffusion-weighted imaging is recommended in all patients with suspected cholesteatoma.

Answer 149

The cisternal segment of the trigeminal nerve (CN5) emerges from the lateral pons at the root entry zone (REZ). It courses anterosuperiorly through the prepontine cistern. It enters the middle cranial fossa by passing beneath tentorium at the apex of the petrous temporal bone. It then passes through an opening in the dura matter called porus trigeminus to enter Meckel cave.

Answer 150

Classic for a choroid plexus papilloma. Choroid plexus papilloma occurs in the lateral ventricle in young children (usually less than 5 years of age). Hydrocephalus is often present either due to obstruction or overproduction of cerebrospinal fluid.

Answer 151

Dandy-Walker malformation is considered a spectrum of malformation that ranges from "mega cisterna magna" (the mildest form) to a "classic" Dandy-Walker continuum in which cystic dilatation of the 4th ventricle communicates dorsally with a variably-sized posterior fossa cyst. The sinus confluence ("torcular Herophili") and tentorium are markedly elevated and displaced above the lambdoid suture, a condition termed "lambdoid-torcular inversion."

Answer 152

The enhancement in this case corresponds precisely to a mildly enlarged optic nerve . Involvement of the nerve itself suggests an inflammatory process, such as idiopathic inflammation (pseudotumor) or acute optic neuritis related to multiple sclerosis; or possibly a neoplastic process, such as optic pathway glioma. By contrast, optic nerve sheath meningioma, as the name suggests, involves the dural sheath, rather than the nerve itself. A meningioma would be distinquishable as enhancement surrounding the nerve, not within the nerve.

Answer 153

The superficial middle cerebral vein (SMCV) is 1 of the 3 named anastomotic superficial cortical veins. It courses anteriorly and inferiorly from the lateral sylvian fissure, curving around the anterior temporal lobe and draining into the cavernous sinus. The SMCV is rarely occluded by venous thrombosis but can provide an important route for collateral venous drainage if multiple dural venous sinuses become occluded. The basal vein of Rosenthal curves around the midbrain (not the anterior temporal lobe) and the vein of Labbe courses posteriorly from the lateral cerebral (sylvian) fissure and terminates in the transverse sinus, not the cavernous sinus.

Answer 154

Tuberous sclerosis is an inherited tumor disorder with multiorgan hamartomas. It commonly presents with the clinical triad of facial angiofibromas (90%), mental retardation (50-80%), and seizures (80-90%). Intracranial findings include calcified subependymal nodules, subependymal giant cell astrocytoma (typically located at foramen of Monro), cortical/subcortical tubers, and white matter radial migration lines. Associated systemic abnormalities can involve the kidneys (angiomyolipoma and cysts), heart (rhabdomyomas), lungs (cystic lymphangiomyomatosis/fibrosis), solid organs (adenomas, leiomyomas), skin (ash-leaf spots, facial angiofibromas, shagreen patches), and extremities (subungual fibromas, cystic bone lesions, undulating periosteal new bone formation).

Answer 155

Squamous cell carcinoma (SCCa) is the most common sinonasal malignancy, 70% of which arise in the maxillary antrum. Although adenocarcinomas may originate in the paranasal sinuses, they have a predilection for the ethmoid sinuses and are rare in comparison with SCCa, accounting for < 20% of sinonasal neoplasms. Sinonasal lymphoma and melanoma are much less common than SCCa, and both have a predilection for originating in the nasal cavity rather than in the paranasal sinuses.

Answer 156

Acute optic neuritis (ANO), as demonstrated on the left in this patient , is strongly associated with new onset demyelinating disease. Up to half of patients with ANO will develop multiple sclerosis; this risk is even higher in women. Acute vision loss with eye pain is the typical presentation of ANO. The majority of patients recover their vision spontaneously, although this recovery can be accelerated by the administration of steroids. Neuromyelitis optica (NMO) is an autoimmune demyelinating disease that is characterized by optic neuritis and spinal cord involvement; NMO is distinct from multiple sclerosis and is characterized by the presence of autoantibodies to the cellular water channel protein aquaporin-4. Orbital pain is common in ANO.

Answer 157

The diagnosis in this case was mycetoma (fungus ball), a noninvasive form of fungal sinusitis. Mycetomas are typically indolent lesions presenting with few symptoms and are most often found in older adults. In this case, the maxillary sinus location, opacification of the sinus, wall thickening (chronic osteitis) , and the presence of calcifications are features suggestive of a mycetoma. Nonfungal chronic rhinosinusitis could have a similar appearance; however, calcifications are much more often seen with mycetoma. The ossifying fibroma usually presents in the 20-40 age group, is expansile, and shows areas of dense ossification rather than punctate calcification. Inverted papillomas typically originate in the nasal cavity near the middle meatus and are more mass-like. Calcification is unusual in inverted papillomas, occurring in about 10% of lesions. Although esthesioneuroblastoma could occur in this age group, they characteristically arise in the superior nasal cavity near the cribriform plate and present with symptoms of nasal obstruction and bleeding.

Answer 158

Ameloblastoma is the most common odontogenic tumor (35%). Its classic imaging description is a "bubbly," multilocular, mixed cystic-solid mass in posterior mandibular ramus associated with unerupted 3rd molar tooth. Larger dentigerous cyst and keratocystic odontogenic tumor are most difficult to differentiate from ameloblastoma. The key imaging differential feature is the presence of nodular enhancement in ameloblastoma. Dentigerous cyst and keratocystic odontogenic tumor do not as a rule have nodular enhancing components.

Answer 159

Lymphoproliferative disease of the orbit includes a spectrum that ranges from polyclonal reactive disease to overt lymphoma, with mucosa-associated lymphoid tissue (MALT) representing a frequently seen extranodal marginal zone variant. Orbital lymphoma is characteristically very responsive to radiation; thus, surgical excision is usually not necessary, and only biopsy is needed to confirm the diagnosis. As with lymphoma elsewhere in the body, strong uniform enhancement is typical in the orbit. Lacrimal gland involvement is common in orbital lymphoma.

Answer 160

Pineal cysts are common incidental findings, seen in over half of all children and 25% of healthy adults on 3T MR. They are identified in 40% of autopsies. Density and signal intensity vary with cyst contents. Calcification is common. Enhancement is nonspecific as the pineal gland parenchyma lacks a blood-brain barrier and normally enhances following contrast administration. This multicystic pineal gland is a normal variant. Pineocytomas are very slow-growing, benign pineal parenchymal tumors that are often partially cystic and can increase in size over time. While pineocytomas and pineal cysts can appear identical on imaging studies, nonneoplastic pineal cysts are much more common than pineal neoplasms. Therefore, the most likely cause for the multiple pineal cysts seen in this case is normal variant.

Answer 161

vein of Labbe, a named cortical vein that courses posterolaterally from the sylvian fissure to drain into the transverse sinus. When it is prominent, its drainage territory is large. Thrombosis of a transverse sinus that extends into the vein of Labbe can cause an extensive venous infarct of the posterior temporal lobe. The internal cerebral veins lie above the level of the vein of Labbe and are seen here as the sinusoidal veins that empty into the vein of Galen (which continues into the straight sinus).

Answer 162

Perimesencephalic nonaneurysmal subarachnoid hemorrhage (pnSAH) Correct: The concentration of blood in front of the pons and around the midbrain with relative sparing of the suprasellar cistern and lateral sylvian fissures is most consistent with this diagnosis. Perimesencephalic nonaneurysmal subarachnoid hemorrhage (pnSAH) is very different from aneurysmal subarachnoid hemorrhage (aSAH). It is not caused by rupture of a saccular aneurysm and is thought to be secondary to a ruptured vein around the midbrain. These patients do not develop vasospasm and do not recur. Once a basilar tip aneurysm (which can rarely cause this type of perimesencephalic hemorrhage) has been ruled out (typically by CTA), the diagnosis of pnSAH can be established.

Answer 163

The presence of calcification, especially "tram-track" calcification, would be highly suggestive of an optic nerve sheath meningioma (ONSM); optic pathway glioma (OPG) does not calcify. Age and gender would also be useful discriminators, as OPG typically presents during childhood, whereas ONSM is usually seen in middle-aged and elderly women. Neurofibromatosis (NF), if present, would also be diagnostically useful: NF type 1 would favor OPG, whereas NF type 2 would point toward ONSM. Neither OPG nor ONSM typically presents with pain; rather, either may present with vision loss or mass effect. At surgery, this lesion was found to be meningioma.

Answer 164

Sickle cell disease spine complications result from hyperplastic marrow, iron deposition, osteopenia, and bone ischemia. Both H-shaped vertebra and serpiginous hyperintensity in the vertebral bodies are features of bone ischemia. The hypointense marrow can relate to hyperplastic marrow or iron deposition. Posterior element ankylosis would be a feature of juvenile inflammatory arthritis.

Answer 165

Microhemorrhages are seen as small signal intensity loss on T2*-weighted gradient-echo images because of magnetic susceptibility effect. History and distribution help differentiate cerebral amyloid disease and chronic hypertension with hypertensive microhemorrhages, the latter predominantly in the deep gray matter, pons, and cerebellum. However, both amyloid and hypertensive-related microhemorrhages can coexist.

Answer 166

The color and location of a retrotympanic mass on otoscopy is very helpful in its identification: an anteroinferior red mass is probably a glomus tympanicum; a red mass that crosses the tympanic membrane from posterior to anterior is likely an aberrant internal carotid artery (ICA); a blue mass posteriorly is probably a dehiscent jugular bulb; a white mass located inferiorly suggests congenital cholesteatoma; a white mass located superiorly is suspicious for a facial nerve schwannoma.

Answer 167

Pineocytomas are typically less than 3 cm, cystic change may be present, and avid enhancement is typical. Pineocytoma may be cystic and mimic pineal cyst. They are rarely invasive. Pineocytoma may compress adjacent structures, including the aqueduct that results in obstructive hydrocephalus. Most common signs/symptoms include headache and Parinaud syndrome (paralysis of upward gaze). Surgical excision or stereotactic biopsy may be performed if symptomatic or when diagnosis is in doubt.

Answer 168

The artery of Percheron is a rare variant of the posterior cerebral circulation. It is a solitary arterial trunk arising from one of the P1 segments of either posterior cerebral artery and supplies the paramedian thalami and the rostral midbrain bilaterally. Recurrent artery of Huebner is a branch from the anterior cerebral artery typically from the proximal A2 segment or distal A1 segment and supplies the anteromedial caudate nucleus and the anterioinferior section of the internal capsule, as well as parts of the putamen.

Answer 169

Over 95% of primary CNS lymphoma (PCNSL) contact a CSF surface, either the ventricular ependyma or pia. Lesions are often deep-seated with a predilection for the periventricular white matter, especially the corpus callosum. In immunocompetent patients, PCNSL shows restricted diffusion and strong homogenous enhancement . Glioblastoma typically shows peripheral ring enhancement, necrosis, and hemorrhage. Abscesses typically show ring enhancement with a central cavity showing restricted diffusion. Metastasis are often multiple, heterogeneous, and have extensive surrounding edema. The most common causes of multiple dural-based masses are meningioma and metastases. Neurosarcoid can involve virtually any intracranial structure, including the dura, where it can present as a solitary or multiple lesion. Extramedullary hematopoiesis is typically found in patients with chronic anemias or marrow depletion disorders. Langerhans cell histiocytosis (LCH) is a great mimicker in the brain and can look like virtually anything. The infundibular stalk is a common site, and LCH often has skull and scalp lesions associated with dural-based masses. Secondary (metastatic) lymphoma often involves the skull and dura, but primary CNS lymphoma, which is the correct answer to this question, rarely arises from the dura. Primary CNS lymphoma typically is a parenchymal disease. Basal ganglia and deep (periventricular) white matter are the most common sites.

Answer 170

Osteoblastomas can occur at any age but most frequently occur in patients between 10-30 years old. Osteoblastoma is an expansile lytic lesion. There is a wide spectrum of internal calcification or ossification. It arises in the posterior elements and most commonly in the thoracic and lumbar spine. Painful scoliosis may be seen in patients with osteoblastoma. Without radiographs or CT, this MR-only imaging is challenging. However, the patient's age (15 years) and history (painful scoliosis) are very helpful. Osteoblastoma should always be considered in the differential diagnosis of a posterior element mass causing painful scoliosis. In this case, the lesion is larger than 1.5 cm, which by definition excludes the diagnosis of osteoid osteoma.

Answer 171

Thalamic involvement typically occurs in posterior reversible encephalopathy syndrome (PRES) patients who also have classic symmetrical parietooccipital T2 hyperintensity. Thalamic lesions are often bilateral but not necessarily symmetrical. Diffusion restriction and enhancement following contrast administration are atypical but occasional findings in PRES. The brainstem and bi-thalamic involvement in this patient is more striking than the subtle occipital lesions. In a few cases, involvement of the brainstem and cerebellum may be the only manifestations of posterior reversible encephalopathy syndrome (PRES). In this case, the occipital involvement makes the diagnosis of PRES most likely. Phoning the emergency room (ER) and obtaining additional history (in this case, the patient was eclamptic) is helpful.

Answer 172

A dysembryoplastic neuroepithelial tumor (DNET) is classically a well-demarcated, micro- or macrolobular intracortical mass found in a young patient with longstanding partial seizures. It is commonly found in the temporal lobe and has minimal or no mass effect relative to its size. Atypical features, such as enhancement, may represent a predilection for recurrence or should suggest a possible alternative diagnosis.

Answer 173

Craniopharyngioma is a benign and often partially cystic sellar region tumor derived from Rathke pouch epithelium. There are 2 types: The adamantinomatous type occurs more frequently in children (peak at 5-15 years) and is typically cystic, whereas the papillary type occurs more commonly in adults (> 50 years) and is more solid. Remember the rule of 90%: 90% are cystic, 90% are calcified, and 90% enhance. Germinoma is primarily seen in young patients (90% of patients < 20 years). Epidermoid would show restricted diffusion and no enhancement.

Answer 174

Oligodendroglioma The calcification, involvement of both cortex and subcortical white matter, patient age, and symptoms are most consistent with this diagnosis. About half of oligodendrogliomas show no enhancement. Teaching Point The most important criteria in assessing oligodendroglioma is not what it looks like on imaging or even histology, it's the tumor genetics. If the tumor exhibits 1p19q deletion, the tumor is chemosensitive and the prognosis is relatively more favorable

Answer 175

This lesion is located in the carotid space and has caused anteromedial internal carotid artery displacement . Intratumoral flow voids make the diagnosis of paraganglioma. There are also significant arterial flow voids seen just inferior to the mass . A paraganglioma centered just below the skull base but above the carotid bifurcation in the nasopharyngeal aspect of the carotid space is termed glomus vagale paraganglioma because it arises from glomus bodies in the vagal nodose ganglion. Paragangliomas are named based on their anatomic location. Carotid body tumor is a paraganglioma centered in the carotid bifurcation. Glomus tympanicum paraganglioma is centered on the cochlear promontory in the middle ear. Glomus jugulare paraganglioma is centered in the jugular foramen of the skull base.

Answer 176

Guillain-Barre syndrome (GBS) is an autoimmune post-infectious or post-vaccinial acute inflammatory demyelination of peripheral nerves, nerve roots, and cranial nerves. Intrathecal and extraforaminal nerve root enhancement can be seen in the acute and chronic polyneuropathies. GBS may actually be the 1st presentation of a chronic or hereditary disorder.

Answer 177

Arteriovenous malformation (AVM) Correct: The CT angiogram appearance is classic for an AVM with a tangle of enlarged feeding vessels/nidus and an enlarged draining vein. In this case, no definite associated aneurysm is seen, but it may be too small to see and/or obliterated from acute blood, only to be seen on digital subtraction angiographic imaging. Even if a vascular malformation is not seen on CT or MR angiography in the setting of an intraparenchymal hematoma, it is still in the differential since it may be obscured by the hemorrhage. Teaching Point Fifteen percent of arteriovenous malformations (AVMs) are infratentorial. In a young patient, a spontaneous cerebellar hemorrhage is unlikely to be hypertensive and is most likely secondary to a vascular malformation. An AVM, cavernous malformation, or dural arteriovenous fistula with cortical venous drainage are the most common culprits.

Answer 178

Ewing sarcoma may elicit reactive bone formation within the involved bone, which may appear similar to tumor osteoid. This bone formation may suggest the diagnosis of Ewing sarcoma versus osteosarcoma. However, it is important to remember that reactive bone formation does NOT occur in the soft tissues. If there is soft tissue mass containing amorphous bone formation, the diagnosis must be osteosarcoma.

Answer 179

The structure is the anterior talofibular ligament (ATFL). The ATFL reportedly is the most commonly torn ligament in the human body and is usually injured in the setting of any significant ankle sprain. It is so often disrupted that it is unusual to see it this well. Of note: When the ATFL is in view, the lower portion of the talus, which is irregularly shaped as in the current case, will be present on the image. If the upper talus, which is square, is in view, then the ligament is usually the anterior inferior tibiofibular ligament.

Answer 180

When considering lesions arising in the osseous elements of the spine, it can be useful to divide lesions into those that predominantly involve the posterior elements (osteoblastoma, aneurysmal bone cyst, osteoid osteoma, myeloma, metastases) and those that predominantly involve the vertebral body (chordoma, giant cell tumor, Langerhans cell histiocytosis, Ewing sarcoma, lymphoma, metastases, myeloma). This can be a good starting point for discussion of the differential diagnosis.

Answer 181

Undifferentiated pleomorphic sarcoma (formerly known as malignant fibrous histiocytoma) is a very common lesion in the adult population. With no specificity to its appearance, it should be considered in most cases of an aggressive soft tissue mass, though the most common site is in the deep soft tissues of the thigh.

Answer 182

CORE = increased MTT or TMax Reduced CBF and CBV PENUMBRA = Increased MTT or TMax Reduced CBF Normal or increased CBV due to vasodilation

mnemonics Flashcards

(207 cards)