Neuropathology Practice Questions

Q: A newborn baby has severe facial abnormalities. What could be the underlying central nervous system (CNS) abnormality in this baby?

Holoprosencephaly. ***Holoprosencephaly*** - The classic teaching "**face predicts the brain**" applies here - holoprosencephaly causes failure of **prosencephalon division**, directly producing severe **midline facial defects** like cyclopia, proboscis, and hypotelorism. - This CNS malformation involves incomplete separation of cerebral hemispheres and is strongly associated with characteristic **craniofacial abnormalities** due to disrupted neural crest cell migration. *Lissencephaly* - Characterized by **smooth brain surface** due to defective neuronal migration, causing severe intellectual disability and seizures. - Does **not cause characteristic facial abnormalities** - the face typically appears normal despite severe brain malformation. *Dandy walker malformation* - Involves **cerebellar hypoplasia** with enlarged fourth ventricle and absent or defective cerebellar vermis. - Primarily affects the **posterior fossa** and does not produce the severe midline facial defects described in this case. *Iniencephaly* - A rare **neural tube defect** involving severe retroflexion of the head with cervical spina bifida and encephalocele. - While it causes severe deformities, it does **not typically produce the characteristic facial abnormalities** associated with prosencephalic malformations.

Q: In chronic alcoholics, what are the acute changes in the brain due to Wernicke's encephalopathy most frequently seen in?

Mamillary bodies. **Explanation:** **Wernicke’s Encephalopathy (WE)** is an acute neurological emergency caused by a deficiency of **Thiamine (Vitamin B1)**, most commonly seen in chronic alcoholics. Thiamine is a critical cofactor for glucose metabolism; its deficiency leads to metabolic failure and subsequent vascular and neuronal damage in specific brain regions. **1. Why Mamillary Bodies are the correct answer:** The **mamillary bodies** are the hallmark site of involvement in WE. They are affected in nearly 100% of cases. Pathologically, acute changes include **petechial hemorrhages**, congestion, and microglial proliferation. Over time, these progress to atrophy and brownish discoloration (hemosiderin deposition), which is a classic finding on autopsy and MRI. **2. Analysis of Incorrect Options:** * **B, C, and D (Aqueduct, 3rd, and 4th Ventricles):** While these periventricular regions are indeed involved in WE, they are less consistently affected than the mamillary bodies. The lesions typically occur in the **periventricular grey matter** surrounding the third and fourth ventricles and the **periaqueductal grey matter** of the midbrain. However, when asked for the *most frequent* or *characteristic* site, the mamillary bodies remain the primary answer. **Clinical Pearls for NEET-PG:** * **Classic Triad:** Confusion, Ataxia, and Ophthalmoplegia (nystagmus/abducens nerve palsy). * **Korsakoff Syndrome:** The chronic phase of the disease characterized by **anterograde amnesia** and **confabulation** (filling memory gaps with imaginary stories). * **Microscopic Hallmark:** Proliferation of small blood vessels (capillary prominence) and hypertrophy of vascular endothelium. * **Treatment Rule:** Always administer Thiamine **before** Glucose. Giving glucose first can precipitate or worsen WE by consuming the remaining thiamine stores during glycolysis.

Q: An infant presents with irritability, increased tone of extremities, and recurrent seizures. Tissue examination reveals globoid cells in the parenchyma around blood vessels. What is the most probable diagnosis?

Krabbe disease. ### Explanation **Krabbe Disease (Globoid Cell Leukodystrophy)** is an autosomal recessive lysosomal storage disorder caused by a deficiency of the enzyme **galactocerebrosidase (GALC)**. This deficiency leads to the accumulation of **galactosylsphingosine (psychosine)**, which is highly toxic to oligodendrocytes, resulting in widespread demyelination [1]. The hallmark histopathological finding is the presence of **Globoid cells**—large, multinucleated macrophages filled with undigested galactocerebroside—typically clustered around blood vessels in the white matter [1]. Clinically, it presents in early infancy with irritability, developmental delay, limb spasticity (increased tone), and seizures. **Analysis of Incorrect Options:** * **Tay-Sachs Disease:** Caused by Hexosaminidase A deficiency. It presents with a "cherry-red spot" on the macula and psychomotor regression, but histologically shows ballooned neurons with lamellated **"onion-skin"** cytoplasmic bodies, not globoid cells. * **Adrenoleukodystrophy:** An X-linked disorder of peroxisomal fatty acid beta-oxidation leading to the accumulation of **Very Long Chain Fatty Acids (VLCFA)**. It typically affects older children and involves adrenal insufficiency. * **Canavan Disease:** Caused by Aspartoacylase deficiency. It is characterized by **spongiform degeneration** (vacuolization) of the white matter and macrocephaly. **High-Yield Pearls for NEET-PG:** * **Enzyme Deficit:** Galactocerebrosidase (GALC). * **Pathognomonic Feature:** Globoid cells (PAS-positive multinucleated macrophages) [1]. * **Imaging:** CT/MRI shows symmetrical attenuation of white matter (demyelination). * **Key Clinical Triad:** Irritability + Hypertonia + Rapid neurodegeneration in an infant. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1304-1305.

Q: A 10-year-old child presents with a posterior fossa mass. A biopsy reveals dense eosinophilic fibers marked with an arrow. What is the nature of these fibers?

Rosenthal fibers. ***Rosenthal fibers*** - Dense **eosinophilic elongated hyaline structures** found in astrocyte processes, characteristic of **pilocytic astrocytoma** - the most common posterior fossa tumor in children. - These fibers are **pathognomonic** for pilocytic astrocytoma and represent abnormal accumulations of intermediate filaments and heat shock proteins within astrocytic processes. *Alzheimer type II astrocyte* - Large astrocytes with **pale, vesicular nuclei** and prominent nucleoli, typically seen in **hepatic encephalopathy** due to ammonia toxicity. - These are **cellular changes** rather than fibrous structures and are not associated with posterior fossa masses in children. *Corpora amylacea* - **Round, basophilic** structures composed of polyglucosans, commonly seen in **aging brain** and reactive gliosis. - These are **spherical bodies**, not elongated eosinophilic fibers, and are typically found in older patients rather than children. *None of the above* - The description of dense eosinophilic fibers in a **pediatric posterior fossa tumor** is classic for Rosenthal fibers. - Given the clinical context and histological appearance, **Rosenthal fibers** is the most appropriate answer among the given options.

Question 1

A female is admitted to the ICU with symptoms of Guillain-Barré syndrome (GBS), experiencing these symptoms for the third time within a few weeks. Nerve biopsy reveals an onion-bulb appearance. What is the most probable diagnosis?

Accepted Answer

Chronic inflammatory demyelinating polyneuropathy

Answer

Amyloidotic neuropathy

Answer

Diabetic neuropathy

Answer

Leprotic neuropathy

Question 2

A newborn baby has severe facial abnormalities. What could be the underlying central nervous system (CNS) abnormality in this baby?

Accepted Answer

Holoprosencephaly

Answer

Lissencephaly

Answer

Dandy walker malformation

Answer

Iniencephaly

Question 3

In chronic alcoholics, what are the acute changes in the brain due to Wernicke's encephalopathy most frequently seen in?

Accepted Answer

Mamillary bodies

Answer

Aqueduct of the midbrain

Answer

Around the third ventricle

Answer

Around the fourth ventricle

Question 4

Degenerated neurofilaments seen in patients with Alzheimer's disease are:

Accepted Answer

Neurofibrillary tangles

Answer

Hirano bodies

Answer

Lipofuscin granules

Answer

Amyloid plaques

Question 5

What is the most common tumor of the pineal region?

Accepted Answer

Germinoma

Answer

Pineocytoma

Answer

Pineoblastoma

Answer

Secondaries

Question 6

An infant presents with irritability, increased tone of extremities, and recurrent seizures. Tissue examination reveals globoid cells in the parenchyma around blood vessels. What is the most probable diagnosis?

Accepted Answer

Krabbe disease

Answer

Tay-Sachs disease

Answer

Adrenoleukodystrophy

Answer

Canavan disease

Question 7

A caseous granuloma is seen in -

Accepted Answer

Brain

Answer

Spleen

Answer

Liver

Answer

Lymph node

Question 8

A 10-year-old child presents with a posterior fossa mass. A biopsy reveals dense eosinophilic fibers marked with an arrow. What is the nature of these fibers?

Accepted Answer

Rosenthal fibers

Answer

Alzheimer type II astrocyte

Answer

Corpora amylacea

Answer

None of the above

Question 9

All of the following are true about Duret hemorrhage, EXCEPT:

Accepted Answer

Seen in conjunctiva

Answer

Increased intracranial pressure

Answer

Cushing's triad

Answer

Seen in the brain

Question 10

Which of the following is not seen in CNS involvement in Wilson's disease?

Accepted Answer

Inclusion bodies

Answer

Perivascular giant cell

Answer

Vacuolar degeneration of posterior column

Answer

Microglial nodule formation

Neuropathology — MCQs

Neuropathology — MCQs

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