Question 1: Alzheimer’s Disease (MTA Score)
Stem: A 76-year-old man presents with progressive short-term memory loss and disorientation. A coronal T1-weighted MRI is performed to assess for atrophy. The radiologist notes significant widening of the choroid fissure, moderate enlargement of the temporal horn of the lateral ventricle, and a moderate loss of hippocampal height.
Question: According to the Scheltens scale (MTA score), which of the following scores is the minimum required to be considered pathologically abnormal for a patient of this age?
(A) MTA Score 0 (B) MTA Score 1 (C) MTA Score 1.5 (D) MTA Score 2 (E) MTA Score 3
Correct Answer: (D) MTA Score 2
Explanation:
- Why (D) is correct: The Medial Temporal lobe Atrophy (MTA) score is a visual rating scale. In patients under 75 years, a score of ≥ 1.5 is abnormal. However, in patients 75 years or older, the cutoff for abnormality increases to ≥ 2 due to age-related involution.
- Why (A) is wrong: MTA 0 represents a normal-looking hippocampus with no visible CSF in the choroid fissure.
- Why (B) is wrong: MTA 1 is common in healthy aging; it shows only a slight widening of the choroid fissure.
- Why (C) is wrong: MTA 1.5 is abnormal for someone under 75, but considered borderline/normal for a 76-year-old.
- Why (E) is wrong: MTA 3 is definitely abnormal (significant loss of hippocampal volume), but it is not the minimum threshold for pathological diagnosis in this age group.
Key Points: Alzheimer’s Disease
- Hallmark: Disproportionate atrophy of the medial temporal lobe (hippocampus and entorhinal cortex).
- FDG-PET: Classic pattern is parieto-temporal hypometabolism.
- Posterior Cingulate: Usually the first area to show hypometabolism.
Question 2: Multiple Sclerosis (Morphology)
Stem: A 30-year-old woman presents with acute left-sided optic neuritis. MRI brain shows several T2-weighted hyperintense lesions. Three lesions are noted to be ovoid in shape and oriented perpendicular to the lateral ventricles.
Question: This specific radiographic sign is known as:
(A) “Hot cross bun” sign (B) “Eye of the tiger” sign (C) “Dawson’s fingers” (D) “Hummingbird” sign (E) “Face of the giant panda” sign
Correct Answer: (C) “Dawson’s fingers”
Explanation:
- Why (C) is correct: Dawson’s fingers are demyelinating plaques centered on the small medullary veins, which run perpendicular to the ventricular walls. This is highly suggestive of Multiple Sclerosis.
- Why (A) is wrong: The “hot cross bun” sign is a cross-shaped hyperintensity in the pons seen in Multiple System Atrophy (MSA-C).
- Why (B) is wrong: “Eye of the tiger” (low T2 in globus pallidus with central high signal) is seen in Pantothenate Kinase-Associated Neurodegeneration (PKAN).
- Why (D) is wrong: The “hummingbird” sign refers to midbrain atrophy in Progressive Supranuclear Palsy (PSP).
- Why (E) is wrong: The “face of the giant panda” sign is the midbrain appearance in Wilson’s disease.
Key Points: Multiple Sclerosis (MS)
- McDonald Criteria: Diagnosis requires dissemination in space and time.
- Locations: Periventricular, juxtacortical, infratentorial, and spinal cord.
- Enhancement: Active plaques show enhancement, often in an incomplete/open-ring pattern.
Question 3: Progressive Supranuclear Palsy (PSP)
Stem: A 68-year-old man presents with frequent falls, vertical gaze palsy, and dementia. Midline sagittal T1-weighted images show marked atrophy of the midbrain tegmentum with a concave superior profile. The pons is normal in size.
Question: This appearance is classically described as the:
(A) “Mickey Mouse” sign (B) “Hot cross bun” sign (C) “Hummingbird” sign (D) “Mount Fuji” sign (E) “Panda” sign
Correct Answer: (C) “Hummingbird” sign
Explanation:
- Why (C) is correct: In PSP, the midbrain (the “head” of the bird) shrinks while the pons (the “body”) remains stable. This creates the “hummingbird” or “penguin” silhouette on sagittal views.
- Why (A) is wrong: The “Mickey Mouse” sign refers to the axial view of the midbrain. In PSP, the midbrain can look like a “thinned” or “shrivelled” Mickey Mouse, but it is not the sagittal descriptor.
- Why (B) is wrong: This refers to the pons in MSA.
- Why (D) is wrong: The “Mount Fuji” sign is seen in tension pneumocephalus.
- Why (E) is wrong: This refers to Wilson’s disease.
Key Points: PSP
- Clinical: Vertical gaze palsy (difficulty looking down) is the key clinical finding.
- Midbrain-to-Pons Ratio: Significant reduction in the ratio due to isolated midbrain atrophy.
Question 4: Multiple System Atrophy (MSA)
Stem: A 60-year-old patient with autonomic failure and cerebellar ataxia undergoes an MRI brain. Axial T2/FLAIR images demonstrate a hyperintense “cross” within the pons.
Question: Selective degeneration of which structures leads to the “hot cross bun” sign?
(A) Substantia nigra (B) Pontocerebellar fibers and pontine raphe (C) Corticospinal tracts (D) Mammillary bodies (E) Dentate nuclei
Correct Answer: (B) Pontocerebellar fibers and pontine raphe
Explanation:
- Why (B) is correct: The “hot cross bun” sign occurs when the transverse pontocerebellar fibers and the median pontine raphe nuclei degenerate, while the corticospinal tracts and tegmentum are spared.
- Why (A) is wrong: Substantia nigra loss is seen in Parkinson’s, but doesn’t cause the cross sign.
- Why (C) is wrong: The corticospinal tracts are the “white meat” of the cross that is spared, not degenerated.
- Why (D) is wrong: Mammillary body atrophy is characteristic of Wernicke’s encephalopathy.
- Why (E) is wrong: While the cerebellum is atrophied in MSA-C, the specific cross-sign is a pontine finding.
Key Points: MSA
- Two types: MSA-P (Parkinsonian – putaminal rim sign) and MSA-C (Cerebellar – hot cross bun sign).
- Autonomic Dysfunction: Always part of the clinical picture (Shy-Drager syndrome).
Question 5: Huntington’s Disease
Stem: A 42-year-old man presents with choreiform movements. MRI demonstrates profound, symmetric atrophy of the caudate nuclei, resulting in a widened intercaudate distance.
Question: The resulting shape of the frontal horns of the lateral ventricles is often described as:
(A) “Slit-like” (B) “Box-car” (C) “Keyhole” (D) “Crescentic” (E) “Arrowhead”
Correct Answer: (B) “Box-car”
Explanation:
- Why (B) is correct: As the head of the caudate nucleus (which normally forms the lateral wall of the frontal horn) atrophies, the ventricles take on a squared-off, “box-car” appearance.
- Why (A) is wrong: Slit-like ventricles are seen in pseudotumor cerebri or young patients with brain swelling.
- Why (C) is wrong: Keyhole appearance is not a standard descriptor for ventricular morphology in neurodegeneration.
- Why (D) is wrong: Crescentic usually describes a subdural hematoma shape.
- Why (E) is wrong: Arrowhead refers to the shape of the 3rd ventricle in certain pathologies, not the frontal horns.
Key Points: Huntington’s Disease
- Inheritance: Autosomal dominant (CAG repeat on Chromosome 4).
- Metabolism: Reduced FDG-PET uptake in the caudate nuclei before atrophy is visible on MRI.
Question 6: Wilson’s Disease
Stem: A 24-year-old man presents with liver failure and tremors. MRI shows T2 hyperintensity in the midbrain tegmentum, but with sparing of the red nuclei and pars reticulata of the substantia nigra.
Question: This midbrain pattern is known as the:
(A) “Mickey Mouse” sign (B) “Hummingbird” sign (C) “Face of the giant panda” sign (D) “Double panda” sign (E) “Inverted V” sign
Correct Answer: (C) “Face of the giant panda” sign
Explanation:
- Why (C) is correct: The “Eyes” of the panda are the red nuclei (spared/dark), the “Ears” are the pars reticulata (spared/dark), and the “Cheeks” are the T2-bright tegmentum.
- Why (D) is wrong: The “Double panda” sign refers to the additional involvement of the pons (miniature panda), but the midbrain alone is the “giant panda.”
- Why (A), (B), (E) are wrong: These refer to other neurodegenerative conditions (PSP or cord disease).
Key Points: Wilson’s Disease
- Copper deposition: Hepatolenticular degeneration.
- Corneal Finding: Kayser-Fleischer rings.
- T1 Signal: May show T1-hyperintensity in the basal ganglia due to paramagnetic effects of copper.
Question 7: Normal Pressure Hydrocephalus (NPH)
Stem: A 75-year-old patient presents with the clinical triad of gait disturbance, urinary incontinence, and cognitive decline. MRI shows ventriculomegaly with a narrowed callosal angle.
Question: Which of the following findings, known as the DESH sign, is most predictive of a positive response to CSF shunting?
(A) Diffuse cortical atrophy (B) Crowding of the gyri at the high convexity (C) Enlargement of the 4th ventricle (D) Transependymal CSF seepage (E) Prominent basal ganglia microbleeds
Correct Answer: (B) Crowding of the gyri at the high convexity
Explanation:
- Why (B) is correct: DESH (Disproportionately Enlarged Subarachnoid space Hydrocephalus) includes ventriculomegaly and widening of the Sylvian fissures, but crowding of the sulci at the vertex (high convexity) is the hallmark.
- Why (A) is wrong: Diffuse atrophy suggests Alzheimer’s or vascular dementia, which would not respond to a shunt.
- Why (C) is wrong: 4th ventricle enlargement occurs in communicating hydrocephalus but isn’t part of the DESH sign.
- Why (D) is wrong: Transependymal oedema is usually absent in chronic NPH; its presence suggests acute obstructive hydrocephalus.
- Why (E) is wrong: Microbleeds are a sign of amyloid angiopathy or hypertension.
Key Points: NPH
- Callosal Angle: Usually < 90 degrees in NPH (measured on coronal images).
- Evans Index: Ratio of maximum width of frontal horns to internal diameter of skull > 0.3.
Question 8: Creutzfeldt-Jakob Disease (CJD)
Stem: A 62-year-old woman presents with rapidly progressive dementia and myoclonus. Diffusion-weighted imaging (DWI) shows linear hyperintensity in the cerebral cortex and the basal ganglia.
(A) Temporal poles (B) Hippocampus (C) Occipital cortex (D) “Cortical ribboning” (E) Periventricular rim
Correct Answer: (D) “Cortical ribboning”
Explanation:
- Why (D) is correct: The linear DWI hyperintensity in the cortex is called “cortical ribboning.” Combined with basal ganglia (caudate/putamen) restricted diffusion, it is highly sensitive for CJD.
- Why (A) is wrong: Temporal pole involvement is classic for CADASIL or FTD.
- Why (B) is wrong: CJD typically spares the hippocampus (unlike Alzheimer’s).
- Why (C) is wrong: Sparing of the peri-rolandic (motor) cortex is common in CJD; involvement isn’t as specific as the “ribbon” pattern.
- Why (E) is wrong: This is seen in lymphoma or CMV.
Key Points: CJD
- Pulvinar Sign: Symmetrical T2/DWI hyperintensity of the posterior thalami (Variant CJD).
- Hockey-stick Sign: Hyperintensity of the mediodorsal thalami.
Question 9: Osmotic Demyelination (CPM)
Stem: A 50-year-old chronic alcoholic patient is admitted with severe hyponatremia. After rapid correction with IV fluids, the patient develops quadriplegia and “locked-in” syndrome. MRI demonstrates T2 hyperintensity in the pons.
Question: Which specific area of the pons is characteristically spared in this condition?
(A) Central basis pontis (B) Peripheral/Corticospinal tracts (C) Paramedian tegmentum (D) Superior cerebellar peduncles (E) Fourth ventricle floor
Correct Answer: (B) Peripheral/Corticospinal tracts
Explanation:
- Why (B) is correct: Central Pontine Myelinolysis (CPM) classically involves the central basis pontis. Crucially, the peripheral fibers and the corticospinal tracts are spared, often giving the lesion a “trident” shape on axial images.
- Why (A) is wrong: This is the primary area involved.
- Why (C), (D), (E) are wrong: These are dorsal/tegmental structures that are not the classic site of demyelination in CPM.
Key Points: CPM
- Cause: Rapid correction of low sodium (Sodium “goes up,” the brain “goes down”).
- Extrapontine Myelinolysis: Can occur in the basal ganglia, thalami, and white matter.
Question 10: CADASIL
Stem: A 40-year-old man presents with recurrent migraines and early-onset stroke. MRI demonstrates extensive symmetric white matter T2 hyperintensity.
Question: Involvement of which of the following regions is a highly specific “classic” finding for CADASIL?
(A) Corpus callosum (B) Temporal poles (C) Optic nerves (D) Medulla (E) Internal capsules
Correct Answer: (B) Temporal poles
Explanation:
- Why (B) is correct: While small vessel disease can affect many areas, hyperintensity in the temporal poles and external capsules is a highly specific marker for CADASIL.
- Why (A) is wrong: Corpus callosum is more common in MS or Susac syndrome.
- Why (C) is wrong: Optic nerve hyperintensity is seen in MS or NMO.
- Why (D) & (E) are wrong: These are less specific and seen in general small vessel disease.
Key Points: CADASIL
- Gene: NOTCH3 mutation.
- Histology: GOM (Granular Osmiophilic Material) on skin biopsy.
Question 11: Frontotemporal Dementia (FTD)
Stem: A 55-year-old woman presents with dramatic social disinhibition and loss of empathy. MRI shows profound asymmetric atrophy of the frontal and temporal lobes.
Question: The severe thinning of the gyri in FTD is often described as having a:
(A) “Tree-trunk” appearance (B) “Cauliflower” appearance (C) “Knife-edge” appearance (D) “Laminated” appearance (E) “Whorled” appearance
Correct Answer: (C) “Knife-edge” appearance
Explanation:
- Why (C) is correct: The extreme atrophy of the frontal and temporal gyri causes them to become extremely thin and sharp, known as the “knife-edge” gyrus sign.
- Why (A) is wrong: Tree-trunk refers to Balo’s Concentric Sclerosis.
- Why (B) is wrong: Not a standard neuro term.
- Why (D) is wrong: Laminated refers to cortical necrosis or Balo’s.
- Why (E) is wrong: Whorled is more common in meningiomas.
Key Points: FTD
- Types: Behavioral variant (Pick’s disease), semantic dementia, and progressive non-fluent aphasia.
- Sparing: Characteristically spares the posterior portions of the brain (parieto-occipital).
Question 12: ADEM (Monophasic)
Stem: An 8-year-old child presents with lethargy and ataxia 10 days after a viral illness. MRI shows large, “fluffy” T2 hyperintense lesions in the subcortical white matter.
Question: Which of the following features most specifically helps differentiate ADEM from Multiple Sclerosis?
(A) Lesions involve the deep white matter (B) Involvement of the thalami (C) Presence of Dawson’s fingers (D) Lesions are in different stages of enhancement (E) Sparing of the U-fibers
Correct Answer: (B) Involvement of the thalami
Explanation:
- Why (B) is correct: ADEM frequently involves the deep grey matter (thalami and basal ganglia), which is rare in MS.
- Why (D) is wrong: In ADEM, all lesions are usually in the same stage (monophasic), so they either all enhance or none enhance. MS has dissemination in time (mixed enhancement).
- Why (A) is wrong: Both involve white matter.
- Why (C) is wrong: This is an MS feature.
- Why (E) is wrong: ADEM typically involves subcortical U-fibers, similar to MS.
Key Points: ADEM
- Clinical: Paediatric, post-infectious, encephalopathy.
- Prognosis: Generally good; usually monophasic.
Question 13: PML (U-fibers)
Stem: An HIV-positive patient presents with progressive motor deficits. MRI shows asymmetric areas of T2 hyperintensity in the subcortical white matter.
Question: Which of the following findings is most characteristic of Progressive Multifocal Leukoencephalopathy (PML)?
(A) Significant mass effect (B) Ring enhancement (C) Involvement of the subcortical U-fibers (D) Sparing of the temporal lobes (E) “Stealth” appearance on FLAIR
Correct Answer: (C) Involvement of the subcortical U-fibers
Explanation:
- Why (C) is correct: PML is caused by the JC virus. It characteristically involves the subcortical U-fibers, appearing as scalloped lesions at the grey-white junction.
- Why (A) & (B) are wrong: PML is typically non-enhancing and shows no mass effect. If enhancement is present, consider “PML-IRIS.”
- Why (D) is wrong: PML can involve any lobe.
- Why (E) is wrong: PML is very bright on FLAIR.
Key Points: PML
- Contrast with HIV Encephalopathy: HIV Encephalitis is symmetric, periventricular, and spares the U-fibers. PML is asymmetric and involves the U-fibers.
Question 14: Wernicke’s Encephalopathy
Stem: A chronic alcoholic patient presents with the triad of confusion, ataxia, and ophthalmoplegia. MRI is performed.
Question: Which of the following is the most sensitive location for T2-hyperintense signal in Wernicke’s encephalopathy?
(A) Mammillary bodies (B) Periaqueductal grey matter (C) Hippocampus (D) Caudate heads (E) Corpus callosum
Correct Answer: (B) Periaqueductal grey matter
Explanation:
- Why (B) is correct: While mammillary body enhancement/atrophy is common, T2 hyperintensity in the periaqueductal grey and the medial thalami (bordering the 3rd ventricle) are the most sensitive findings.
- (A) is a classic finding but usually refers to enhancement or chronic atrophy.
- (C), (D), (E) are not typical primary sites for Wernicke’s.
Key Points: Wernicke’s Encephalopathy
- Cause: Thiamine (B1) deficiency.
- Enhancement: Mammillary bodies show avid enhancement in the acute phase.
Question 15: Marchiafava-Bignami Disease
Stem: A patient with chronic malnutrition and heavy red wine consumption presents with seizures and dementia. MRI shows T2-hyperintensity and swelling of the corpus callosum, specifically sparing the dorsal and ventral layers.
Question: This “sandwich” appearance of the corpus callosum is characteristic of:
(A) Multiple Sclerosis (B) Marchiafava-Bignami Disease (C) Susac Syndrome (D) Glioblastoma (E) Lymphoma
Correct Answer: (B) Marchiafava-Bignami Disease
Explanation:
- Why (B) is correct: MBD is a toxic demyelination of the corpus callosum seen in chronic alcoholics. The “sandwich sign” refers to the involvement of the central layers of the callosum with sparing of the outer layers.
- Why (A) is wrong: MS lesions (“Dawson’s fingers”) are different.
- Why (C) is wrong: Susac syndrome shows small “snowball” lesions in the central callosum.
Key Points: MBD
- Location: Starts in the body of the corpus callosum, may spread to the genu and splenium.
- Outcome: High mortality or severe permanent disability.
