Question 1: Alzheimer’s Disease
Stem: A 75-year-old man presents with progressive short-term memory loss and disorientation. An MRI of the brain is performed. The coronal T1-weighted images demonstrate significant atrophy of the hippocampal formations bilaterally, with associated widening of the choroid fissures and enlargement of the temporal horns.
Question: According to the Scheltens scale (MTA score), which of the following is the most important anatomical region to assess for the diagnosis of Alzheimer’s disease?
(A) The frontal lobes (B) The caudate nuclei (C) The medial temporal lobe (D) The substantia nigra (E) The cerebellar vermis
Correct Answer: (C) The medial temporal lobe.
Explanation:
- Why (C) is correct: The Scheltens scale (Medial Temporal lobe Atrophy or MTA score) is a visual rating scale used to assess the degree of hippocampal atrophy, which is a hallmark of Alzheimer’s disease. It evaluates the width of the choroid fissure, the width of the temporal horn, and the height of the hippocampal formation.
- Why (A) is wrong: Frontal lobe atrophy is more characteristic of Frontotemporal Dementia (FTD).
- Why (B) is wrong: Caudate atrophy is characteristic of Huntington’s disease.
- Why (D) is wrong: The substantia nigra is involved in Parkinson’s disease but is not part of the MTA score.
- Why (E) is wrong: Cerebellar atrophy is seen in various ataxias (e.g., MSA-C) but not typically in early Alzheimer’s.
Key Points: Alzheimer’s Disease
- Most common cause of dementia.
- Imaging Hallmark: Disproportionate medial temporal lobe atrophy (hippocampus, entorhinal cortex).
- MTA Score: 0 (none) to 4 (severe). A score of ≥2 is abnormal in patients <75 years.
- FDG-PET: Shows characteristic hypometabolism in the parieto-temporal regions and posterior cingulate cortex.
Question 2: Multiple Sclerosis (MS)
Stem: A 28-year-old woman presents with optic neuritis. An MRI of the brain demonstrates multiple, ovoid, T2-bright lesions. Several lesions are oriented perpendicular to the lateral ventricles, extending into the deep white matter.
Question: This specific orientation of MS plaques is known as:
(A) “Hot cross bun” sign (B) “Dawson’s fingers” (C) “Hummingbird” sign (D) “Mickey Mouse” sign (E) “Panda” sign
Correct Answer: (B) “Dawson’s fingers”.
Explanation:
- Why (B) is correct: Dawson’s fingers are the classic radiographic sign of Multiple Sclerosis. They represent demyelinating plaques centered on the small medullary veins, which run perpendicular to the walls of the lateral ventricles.
- Why (A) is wrong: The “hot cross bun” sign is seen in the pons in Multiple System Atrophy (MSA-P).
- Why (C) is wrong: The “hummingbird” (or penguin) sign is seen in Progressive Supranuclear Palsy (PSP) due to midbrain atrophy.
- Why (D) is wrong: The “Mickey Mouse” sign refers to the normal midbrain, but a flattened Mickey Mouse head is seen in PSP.
- Why (E) is wrong: The “face of the giant panda” sign is seen in Wilson’s disease.
Key Points: Multiple Sclerosis (MS)
- Pathology: Inflammatory demyelinating disease of the CNS.
- Classic Locations:
- Periventricular (Dawson’s fingers).
- Juxtacortical (touching the cortex).
- Infratentorial (pons, cerebellum).
- Spinal cord (short segment, posterior/lateral).
- Active Plaques: Show contrast enhancement (often incomplete/open-ring) and restricted diffusion.
Question 3: Progressive Supranuclear Palsy (PSP)
Stem: A 68-year-old man presents with frequent falls, vertical gaze palsy, and “stiff” Parkinsonian features. An MRI of the brain is performed. Sagittal T1-weighted images show marked atrophy of the midbrain tegmentum, with a concave superior profile, while the pons remains relatively normal in size.
Question: This appearance is classically described as the:
(A) “Mickey Mouse” sign (B) “Hot cross bun” sign (C) “Hummingbird” sign (D) “Panda” sign (E) “Face of the mini panda” sign
Correct Answer: (C) “Hummingbird” sign.
Explanation:
- Why (C) is correct: In Progressive Supranuclear Palsy (PSP), the midbrain undergoes significant atrophy while the pons is preserved. On a midline sagittal view, the atrophied midbrain (head) and the preserved pons (body) resemble the shape of a hummingbird (or penguin).
- Why (A) is wrong: On axial images, the normal midbrain looks like Mickey Mouse. In PSP, the atrophy of the tegmentum makes it look like a “flattened Mickey Mouse.”
- Why (B) is wrong: This is seen in the pons in MSA.
- Why (D) & (E) are wrong: These are seen in the midbrain and pons, respectively, in Wilson’s disease.
Key Points: Progressive Supranuclear Palsy (PSP)
- Parkinson-plus syndrome.
- Midbrain Atrophy: The hallmark of the disease.
- Imaging Signs:
- Hummingbird sign (Sagittal).
- Mickey Mouse sign (Axial – thin “ears” [peduncles] and flat tegmentum).
- Reduced midbrain-to-pons ratio.
Question 4: Multiple System Atrophy (MSA)
Stem: A 65-year-old patient with autonomic dysfunction and cerebellar ataxia undergoes an MRI. Axial T2-weighted images through the pons show a cross-shaped area of high signal within the pontine hyperintensity.
Question: This finding is known as the:
(A) “Hummingbird” sign (B) “Hot cross bun” sign (C) “Mickey Mouse” sign (D) “Trident” sign (E) “Tegmental” sign
Correct Answer: (B) “Hot cross bun” sign.
Explanation:
- Why (B) is correct: The “hot cross bun” sign is the result of selective degeneration of the pontocerebellar tracts and pontine raphe, while the corticospinal tracts are preserved. This creates a hyperintense cross on T2/FLAIR images in the pons. It is characteristic of MSA-C (the cerebellar subtype).
- Why (A) is wrong: This is a sagittal sign of PSP.
- Why (C) is wrong: This refers to the midbrain.
- Why (D) & (E) are wrong: These are not standard neurodegenerative signs.
Key Points: Multiple System Atrophy (MSA)
- Subtypes: MSA-P (Parkinsonian) and MSA-C (Cerebellar).
- MSA-C Hallmark: “Hot cross bun” sign in the pons and cerebellar atrophy.
- MSA-P Hallmark: T2-hypointensity of the putamen with a hyperintense “putaminal rim” sign.
Question 5: Huntington’s Disease
Stem: A 40-year-old man presents with choreiform movements and executive dysfunction. An MRI of the brain demonstrates marked atrophy of the head of the caudate nuclei bilaterally, resulting in a “box-car” configuration of the frontal horns of the lateral ventricles.
Question: This appearance is most characteristic of:
(A) Wilson’s disease (B) Huntington’s disease (C) Alzheimer’s disease (D) Pick’s disease (E) CADASIL
Correct Answer: (B) Huntington’s disease.
Explanation:
- Why (B) is correct: Huntington’s disease is an autosomal dominant neurodegenerative disorder. Its imaging hallmark is symmetric atrophy of the caudate nuclei (specifically the heads). As the caudate heads shrink, the frontal horns of the lateral ventricles expand and lose their normal “comma” shape, becoming “box-car” shaped.
- Why (A) is wrong: Wilson’s disease involves the thalami and midbrain (“panda”).
- Why (C) is wrong: Alzheimer’s involves the medial temporal lobes.
- Why (D) is wrong: Pick’s (FTD) involves the frontal and temporal lobes.
- Why (E) is wrong: CADASIL is a white matter disease.
Key Points: Huntington’s Disease
- Inheritance: Autosomal dominant (CAG repeat).
- Classic Imaging: Caudate head atrophy.
- Sign: “Box-car” ventricles.
- Intercaudate distance to inner table (CC/IT) ratio is used for measurement.
Question 6: Wilson’s Disease
Stem: A 22-year-old man presents with tremors, dysarthria, and liver failure. An MRI of the brain reveals symmetric T2-high signal in the thalami and midbrain tegmentum, with sparing of the red nuclei and the pars reticulata of the substantia nigra.
Question: This specific midbrain appearance is known as the:
(A) “Hummingbird” sign (B) “Face of the giant panda” sign (C) “Hot cross bun” sign (D) “Mickey Mouse” sign (E) “Eye of the tiger” sign
Correct Answer: (B) “Face of the giant panda” sign.
Explanation:
- Why (B) is correct: In Wilson’s disease (hepatolenticular degeneration), copper deposition and gliosis cause T2-high signal in the midbrain tegmentum. The sparing of the red nuclei (eyes of the panda), the pars reticulata (ears), and the superior colliculi (mouth) creates the “face of the giant panda” appearance.
- Why (A) is wrong: Sagittal PSP sign.
- Why (C) is wrong: Pontine MSA sign.
- Why (E) is wrong: The “eye of the tiger” sign (low T2 in globus pallidus with a central high spot) is the hallmark of Hallervorden-Spatz (NBIA).
Key Points: Wilson’s Disease
- Pathology: Disorder of copper metabolism (ATP7B mutation).
- Classic Imaging:
- “Face of the giant panda” (Midbrain).
- “Face of the miniature panda” (Pons).
- Symmetric T2/FLAIR high signal in the basal ganglia, thalami, and brainstem.
Question 7: Normal Pressure Hydrocephalus (NPH)
Stem: An 80-year-old man presents with the triad of “wet, wobbly, and wacky” (urinary incontinence, gait ataxia, and dementia). An MRI demonstrates ventriculomegaly disproportionate to the degree of sulcal enlargement. There is crowding of the sulci at the vertex and widening of the Sylvian fissures.
Question: This imaging pattern is known as:
(A) DESH (Disproportionately Enlarged Subarachnoid space Hydrocephalus) (B) Linitis Plastica (C) Encephalomalacia (D) Transependymal oedema (E) Communicating hydrocephalus
Correct Answer: (A) DESH (Disproportionately Enlarged Subarachnoid space Hydrocephalus).
Explanation:
- Why (A) is correct: DESH is a highly specific imaging feature for iNPH (idiopathic Normal Pressure Hydrocephalus). It consists of: 1) Ventriculomegaly, 2) Widening of the Sylvian fissures, and 3) Crowding of the sulci at the vertex (high convexity).
- Why (D) is wrong: Transependymal oedema (periventricular T2-high signal) is common in obstructive hydrocephalus but is notably absent or minimal in NPH.
- Why (E) is wrong: NPH is a type of communicating hydrocephalus, but DESH is the specific descriptive sign.
Key Points: Normal Pressure Hydrocephalus (NPH)
- Triad: Incontinence, Gait disturbance, Dementia.
- Evans Index: Ratio of maximum width of frontal horns to internal diameter of skull > 0.3.
- DESH Sign: Crowded vertex sulci + dilated Sylvian fissures + ventriculomegaly.
- Management: May improve with a ventriculoperitoneal (VP) shunt.
Question 8: Creutzfeldt-Jakob Disease (CJD)
Stem: A 60-year-old man presents with rapidly progressive dementia and myoclonus. An MRI demonstrates linear hyperintensity on Diffusion-Weighted Imaging (DWI) along the cerebral cortex (cortical ribboning) and the caudate heads and putamen bilaterally.
Question: This pattern of “cortical ribboning” and basal ganglia restricted diffusion is most typical of:
(A) Alzheimer’s disease (B) Creutzfeldt-Jakob Disease (CJD) (C) Viral Encephalitis (D) Global Hypoxia (E) Status Epilepticus
Correct Answer: (B) Creutzfeldt-Jakob Disease (CJD).
Explanation:
- Why (B) is correct: CJD is a prion disease. Its classic MRI feature is restricted diffusion (DWI bright/ADC dark) in a “cortical ribboning” pattern and in the basal ganglia (caudate and putamen). This is much more sensitive than T2/FLAIR.
- Why (C) is wrong: Viral encephalitis (e.g., HSV) typically involves the limbic system (temporal lobes), not widespread cortical ribboning.
- Why (D) is wrong: Global hypoxia causes restricted diffusion but is usually symmetric and follows cardiac arrest.
- Why (E) is wrong: Status can cause cortical DWI signal, but the clinical context of rapidly progressive dementia points to CJD.
Key Points: Creutzfeldt-Jakob Disease (CJD)
- Pathology: Prion-mediated neurodegeneration.
- DWI is the most sensitive sequence.
- Signs:
- Cortical Ribboning: Restricted diffusion in the cortex.
- Pulvinar sign (Variant CJD): High T2/DWI in the posterior thalamus.
- Hockey-stick sign: High signal in the mediodorsal thalami.
Question 9: Osmotic Demyelination Syndrome
Stem: A 45-year-old chronic alcoholic patient is admitted with severe hyponatraemia, which is corrected rapidly with intravenous fluids. Three days later, the patient develops “locked-in” syndrome. An MRI demonstrates a well-defined area of T2-high signal and restricted diffusion in the central portion of the basis pontis, with sparing of the peripheral corticospinal tracts.
Question: What is the diagnosis?
(A) Pontine Infarct (B) Central Pontine Myelinolysis (CPM) (C) Multiple System Atrophy (MSA) (D) Progressive Supranuclear Palsy (PSP) (E) Rhombencephalitis
Correct Answer: (B) Central Pontine Myelinolysis (CPM).
Explanation:
- Why (B) is correct: CPM (part of the Osmotic Demyelination Syndrome) is caused by the rapid correction of hyponatraemia. It results in demyelination in the central basis pontis. The “sparing” of the peripheral fibers is a key imaging feature.
- Why (A) is wrong: An infarct would typically be asymmetric and involve a specific vascular territory (e.g., paramedian branches).
- Why (C) is wrong: MSA shows the “hot cross bun” sign, which is chronic and has a different clinical presentation.
Key Points: Central Pontine Myelinolysis (CPM)
- Cause: Rapid correction of hyponatraemia.
- Imaging:
- T2/FLAIR high signal in the central pons.
- Trident-shaped appearance on axial images.
- Peripheral sparing of the corticospinal tracts and ventrolateral pons.
- Extrapontine Myelinolysis: Can also occur in the basal ganglia or thalami.
Question 10: ADEM vs. Multiple Sclerosis
Stem: An 8-year-old child presents with encephalopathy and focal neurological deficits 2 weeks after a viral infection. MRI shows large, poorly defined, asymmetric T2-bright lesions in the subcortical white matter. All lesions appear to be in the same stage of development, and all show faint enhancement following gadolinium.
Question: What is the most likely diagnosis?
(A) Multiple Sclerosis (MS) (B) Acute Disseminated Encephalomyelitis (ADEM) (C) Progressive Multifocal Leukoencephalopathy (PML) (D) Balo’s Concentric Sclerosis (E) Susac Syndrome
Correct Answer: (B) Acute Disseminated Encephalomyelitis (ADEM).
Explanation:
- Why (B) is correct: ADEM is a post-infectious/post-vaccination demyelinating process. Key features that differentiate it from MS are: 1) Paediatric age group, 2) Clinical encephalopathy (uncommon in MS), 3) Monophasic nature (all lesions are in the same stage of development and enhance simultaneously), and 4) Involvement of the deep grey matter (thalami).
- Why (A) is wrong: MS is characterized by “dissemination in space and time,” meaning you would expect to see lesions in different stages (some enhancing, some not).
- Why (C) is wrong: PML is seen in immunocompromised adults and does not typically enhance.
Key Points: ADEM
- Monophasic autoimmune demyelination.
- Clinical: Paediatric, post-viral, encephalopathy.
- Imaging: Large, fluffy white matter lesions. Simultaneous enhancement is the key differentiator from MS.
Question 11: Progressive Multifocal Leukoencephalopathy (PML)
Stem: A 40-year-old HIV-positive patient (CD4 count < 50) presents with progressive cognitive decline. MRI shows asymmetric areas of T2/FLAIR high signal in the subcortical white matter, which involve the U-fibers. There is no mass effect and no contrast enhancement.
Question: This appearance is most characteristic of:
(A) HIV Encephalitis (B) Progressive Multifocal Leukoencephalopathy (PML) (C) Toxoplasmosis (D) CNS Lymphoma (E) Cytomegalovirus (CMV) Encephalitis
Correct Answer: (B) Progressive Multifocal Leukoencephalopathy (PML).
Explanation:
- Why (B) is correct: PML is caused by reactivation of the JC virus. Its imaging hallmarks are: 1) Asymmetric subcortical white matter lesions, 2) Involvement of the U-fibers (subcortical arcuate fibers), and 3) Absence of enhancement or mass effect.
- Why (A) is wrong: HIV Encephalitis is typically symmetric, involves the deep white matter, and spares the U-fibers.
- Why (C) & (D) are wrong: These present as enhancing mass lesions.
Key Points: PML
- Cause: JC virus in immunocompromised states.
- Imaging: Asymmetric T2/FLAIR high signal, involves U-fibers, no mass effect, no enhancement.
- Contrast with HIV Encephalitis: PML is peripheral/asymmetric (involves U-fibers); HIV is deep/symmetric (spares U-fibers).
Question 12: CADASIL
Stem: A 45-year-old woman with a history of recurrent migraines and early-onset strokes has an MRI. It demonstrates extensive, symmetric white matter T2-high signal.
Question: In CADASIL, which specific location of white matter hyperintensity is a highly suggestive and classic finding?
(A) The temporal poles (B) The occipital lobes (C) The corpus callosum (D) The optic nerves (E) The pituitary stalk
Correct Answer: (A) The temporal poles.
Explanation:
- Why (A) is correct: CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) has a very high predilection for the temporal poles and the external capsules. Finding white matter hyperintensity in these regions in a young patient with strokes is highly suggestive.
- Why (C) is wrong: Corpus callosum involvement is more common in MS or Susac syndrome.
Key Points: CADASIL
- Inheritance: Autosomal dominant (NOTCH3 mutation).
- Clinical: Migraines, early strokes, dementia.
- Imaging Hallmark: Symmetric white matter signal in the temporal poles and external capsules.
Question 13: Frontotemporal Dementia (FTD)
Stem: A 55-year-old man presents with dramatic changes in personality and social disinhibition. An MRI shows profound, asymmetric atrophy of the frontal and temporal lobes, with extreme thinning of the gyri resulting in a “knife-edge” appearance. The parietal and occipital lobes are relatively spared.
Question: What is the most likely diagnosis?
(A) Alzheimer’s disease (B) Frontotemporal Dementia (FTD / Pick’s Disease) (C) Huntington’s disease (D) Vascular dementia (E) Dementia with Lewy bodies
Correct Answer: (B) Frontotemporal Dementia (FTD / Pick’s Disease).
Explanation:
- Why (B) is correct: FTD is characterized by profound, often asymmetric atrophy of the frontal and temporal lobes. This leads to the “knife-edge” gyrus sign. The social/behavioral presentation is also classic.
- Why (A) is wrong: Alzheimer’s shows medial temporal atrophy and more generalized posterior parietal atrophy.
Key Points: Frontotemporal Dementia
- Age: Usually younger onset (45-65) than Alzheimer’s.
- Clinical Subtypes: Behavioral variant (disinhibition), Semantic (language), Primary progressive aphasia.
- Imaging: “Knife-edge” atrophy of frontal and/or temporal lobes.
Question 14: Vascular Dementia
Stem: A 75-year-old hypertensive woman has an MRI for cognitive decline. It shows multiple small (< 15 mm) fluid-filled cavities in the basal ganglia and deep white matter, representing lacunar infarcts. There is also extensive, confluent periventricular white matter hyperintensity.
Question: Which visual rating scale is standardly used to report the severity of white matter hyperintensity (leukoaraiosis) on MRI?
(A) Scheltens scale (B) Fazekas scale (C) Koos classification (D) Ficat classification (E) Rockwood scale
Correct Answer: (B) Fazekas scale.
Explanation:
- Why (B) is correct: The Fazekas scale is the standard scale for grading white matter small vessel disease (0 = none, 1 = punctate, 2 = beginning confluence, 3 = large confluent areas).
- Why (A) is wrong: Scheltens is for hippocampal atrophy.
- Why (D) is wrong: Ficat is for AVN of the hip.
Key Points: Vascular Dementia
- Cause: Small vessel ischaemic disease.
- Imaging:
- Lacunar Infarcts: Small cavities (3-15mm) following CSF signal.
- Leukoaraiosis: Confluent T2/FLAIR high signal in white matter (Fazekas scale).
- Microbleeds: Seen on SWI/GRE.
Question 15: Balo’s Concentric Sclerosis
Stem: A 30-year-old man presents with acute neurological symptoms. MRI reveals a large, 4 cm lesion in the white matter of the right parietal lobe. The lesion demonstrates alternating concentric rings of T2-high and T2-intermediate signal, resembling a “tree-trunk” or “onion-skin” pattern.
Question: This pathognomonic appearance is characteristic of:
(A) Multiple Sclerosis (B) Balo’s Concentric Sclerosis (C) ADEM (D) Susac Syndrome (E) PML
Correct Answer: (B) Balo’s Concentric Sclerosis.
Explanation:
- Why (B) is correct: This is a rare, acute variant of MS. The pathognomonic sign is the concentric, lamellated appearance of the lesion (alternating rings of demyelination and preserved myelin).
- Why (D) is wrong: Susac syndrome shows “snowball” lesions in the corpus callosum.
Key Points: Balo’s Concentric Sclerosis
- Rare variant of MS.
- Pathognomonic Sign: Concentric rings (lamellated appearance) on T2/FLAIR and post-contrast MRI.
