Neuropathology Practice Questions

Q: What is the secondary structure of prion proteins in prion diseases like Creutzfeldt-Jakob disease (CJD)?

Beta sheets. **Explanation:** Prion diseases, such as Creutzfeldt-Jakob disease (CJD), are caused by the conformational change of a normal cellular protein ($PrP^C$) into an abnormal, infectious isoform ($PrP^{Sc}$) [1]. 1. **Why Beta sheets are correct:** The fundamental pathogenesis of prion disease involves a post-translational modification where the **alpha-helical** content of the normal protein is converted into **beta-pleated sheets** [1]. This structural shift makes the protein ($PrP^{Sc}$) resistant to proteolysis (protease-resistant), insoluble, and capable of inducing similar conformational changes in neighboring normal proteins, leading to neurotoxic aggregation [1]. 2. **Why the other options are incorrect:** * **Alpha helix:** This is the predominant secondary structure of the **normal** prion protein ($PrP^C$) [1]. In the disease state, these helices are replaced by beta sheets. * **Beta bend and Beta turn:** These are specific types of secondary structures that involve a change in direction of the polypeptide chain (usually involving 4 amino acids). While they exist in many proteins, they are not the defining structural hallmark of the pathogenic prion transition. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Characterized by **spongiform encephalopathy** (vacuolation of neurons and neuropil) without inflammatory infiltrate. * **Diagnosis:** Detection of **14-3-3 protein** in CSF is a sensitive marker for CJD. * **Genetics:** Most cases are sporadic, but familial forms are linked to mutations in the **PRNP gene** on chromosome 20 [1]. * **Staining:** Prion aggregates can be visualized with Congo Red (showing apple-green birefringence) as they behave like amyloid, though they are distinct from classic Alzheimer’s amyloid. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, p. 1284.

Q: Glioblastoma multiforme may occur in the following locations, except:

Adrenal medulla of child. **Explanation:** The correct answer is **D. Adrenal medulla of child**. **Glioblastoma (GBM)** is a Grade 4 astrocytoma, which is a primary tumor of the central nervous system (CNS) arising from glial cells (astrocytes) [1]. The adrenal medulla, however, is derived from **neural crest cells** and is part of the peripheral nervous system. In children, the most common tumor arising from the adrenal medulla is **Neuroblastoma**, not Glioblastoma. **Analysis of Options:** * **A. Cerebrum of adult:** This is the most common site for GBM [2]. It typically presents as a large, necrotic mass in the cerebral hemispheres, often crossing the corpus callosum (Butterfly Glioma) [1]. * **B. Brain stem of child:** While GBM is primarily an adult tumor, high-grade gliomas (including Diffuse Intrinsic Pontine Gliomas or DIPG) occur in the brainstem of children and are histologically similar to GBM [2]. * **C. Spinal cord of adult:** Although rare compared to intracranial sites, GBM can occur anywhere in the CNS axis, including the spinal cord. **NEET-PG High-Yield Pearls:** 1. **Hallmark Histology:** Look for **pseudopalisading necrosis** and **microvascular (glomeruloid) proliferation** [1]. 2. **Molecular Marker:** **IDH-mutation status** is now critical for classification (WHO 2021). Most GBMs are IDH-wildtype [1]. 3. **Radiology:** Classically presents as a **ring-enhancing lesion** on MRI due to central necrosis [1]. 4. **GFAP Positivity:** As a glial tumor, GBM is strongly positive for Glial Fibrillary Acidic Protein (GFAP). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1308-1311. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726.

Question 1

What is the most common location for diffuse axonal injuries?

Accepted Answer

Junction of grey and white matter

Answer

Brain stem

Answer

Corpus callosum

Answer

Anterior one-third of the spinal cord

Question 2

What is the secondary structure of prion proteins in prion diseases like Creutzfeldt-Jakob disease (CJD)?

Accepted Answer

Beta sheets

Answer

Beta bend

Answer

Beta turn

Answer

Alpha helix

Question 3

A 35-year-old man with Down syndrome dies of acute lymphoblastic leukemia. Gross examination of the patient's brain at autopsy shows mild microcephaly and underdevelopment of the superior temporal gyri. Histologic examination would most likely show which of the following neuropathologic changes?

Accepted Answer

Neurofibrillary tangles

Answer

AA amyloidosis

Answer

Lewy bodies

Answer

Negri bodies

Question 4

Mutations in the merlin protein are associated with which of the following tumors?

Accepted Answer

Meningioma

Answer

Astrocytoma

Answer

Medulloblastoma

Answer

Oligodendroglioma

Question 5

A 40-year-old lady is diagnosed to have a frontal lobe brain tumor. The lesion is characterized by focal necrosis surrounded by ring-like enhancement. What is the most likely diagnosis?

Accepted Answer

Glioblastoma multiforme

Answer

Oligodendroglioma

Answer

Ependymoma

Answer

Astrocytoma

Question 6

Glioblastoma multiforme may occur in the following locations, except:

Accepted Answer

Adrenal medulla of child

Answer

Cerebrum of adult

Answer

Brain stem of child

Answer

Spinal cord of adult

Question 7

Medulloblastoma associated Turcot syndrome is characterized by mutation in which of the following genes?

Accepted Answer

APC

Answer

KRAS

Answer

TP53

Answer

PTEN

Question 8

An 8-month-old boy exhibits severe motor, sensory, and cognitive impairments. Brain biopsy shows a disease of white matter characterized by the accumulation of "globoid cells." Biochemical studies reveal an absence of galactocerebroside b-galactosidase activity. What is the appropriate diagnosis?

Accepted Answer

Krabbe disease

Answer

Alexander disease

Answer

Hurler disease

Answer

Metachromatic leukodystrophy

Question 9

Which of the following cancers metastasize to the brain the least?

Accepted Answer

Prostatic carcinoma

Answer

Hypernephroma

Answer

Breast carcinoma

Answer

Choriocarcinoma

Question 10

Group atrophy of muscle fibers denotes:

Accepted Answer

Enlarged motor units with all muscle fibers reduced to the same size

Answer

Enlarged motor units with all muscle fibers disproportionately reduced

Answer

Reduced motor units with all muscle fibers reduced to the same size

Answer

Reduced motor units with all muscle fibers disproportionately reduced

Neuropathology — MCQs

Neuropathology — MCQs

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