Neuropathology Practice Questions

Q: What is the most common intracranial tumor?

Metastatic tumors. **Explanation:** **Correct Answer: A. Metastatic tumors** In adults, **metastatic tumors** are the most common intracranial neoplasms, accounting for approximately 50% of all brain tumors [1]. They typically reach the brain via hematogenous spread and are often found at the grey-white matter junction. The most common primary sources are the **Lung (most common overall)**, Breast, Skin (Melanoma), Kidney (RCC), and Colon [1]. **Why the other options are incorrect:** * **B. Neuroblastoma:** This is a common extracranial solid tumor in children, usually arising from the adrenal medulla or sympathetic chain. While it can metastasize to the skull (causing "raccoon eyes"), it is not a primary or the most common intracranial tumor. * **C. Schwannoma:** These are benign tumors of the peripheral nerves (most commonly CN VIII). While common among nerve sheath tumors, they represent only about 8% of intracranial neoplasms. * **D. Ependymoma:** These are primary glial tumors arising from the lining of the ventricles. They are more common in children (typically in the 4th ventricle) but are far less frequent than metastases or astrocytomas. **High-Yield Clinical Pearls for NEET-PG:** * **Most common primary CNS tumor in adults:** Glioblastoma Multiforme (GBM). * **Most common primary CNS tumor in children:** Pilocytic Astrocytoma (followed by Medulloblastoma) [1]. * **Most common site for brain metastasis:** The distribution follows blood flow; hence, the **Cerebrum (80%)** is the most common site, followed by the Cerebellum. * **Radiology:** Metastases typically appear as multiple, well-circumscribed, ring-enhancing lesions with significant peritumoral edema. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1317-1320.

Q: What is chromatolysis?

Disappearance of Nissl granules. **Explanation:** **Chromatolysis** is a reactive change seen in the cell body (perikaryon) of a neuron in response to axonal injury (axonal reaction) [1]. It represents a regenerative effort by the cell to increase protein synthesis for axonal repair [1]. 1. **Why Option C is Correct:** The hallmark of chromatolysis is the **disappearance or dispersion of Nissl granules** (which are clusters of Rough Endoplasmic Reticulum and free ribosomes) [1]. Under light microscopy, the cytoplasm appears pale and homogeneous because the basophilic staining of the Nissl substance is lost as it undergoes dissolution and moves toward the periphery. 2. **Why Other Options are Incorrect:** * **A. Disintegration of the nucleus:** In chromatolysis, the nucleus does not disintegrate; instead, it typically becomes **eccentric** (pushed to the periphery) and the nucleolus becomes prominent [1]. * **B. Disintegration of the Golgi apparatus:** While the Golgi may undergo structural changes during cellular stress, it is not the defining feature of chromatolysis. * **D. Decrease in cell size:** Chromatolysis is characterized by **cellular swelling** (increased size) and a rounded contour, not a decrease in size [1]. **NEET-PG High-Yield Pearls:** * **Key Morphological Triad:** 1. Dissolution of Nissl bodies (Chromatolysis), 2. Displacement of the nucleus to the periphery, 3. Swelling of the cell body [1]. * **Significance:** It is a sign of **axonal reaction** (retrograde change) following trauma or axotomy [1]. * **Wallerian Degeneration:** This refers to the changes occurring *distal* to the site of axonal injury, whereas chromatolysis occurs in the *cell body*. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1254-1255.

Q: Rosenthal fibers in astrocytoma are composed of which of the following?

Glial fibrillary acidic protein (GFAP). **Explanation:** **Rosenthal fibers** are characteristic histopathological findings in certain low-grade gliomas, most notably **Pilocytic Astrocytoma** (WHO Grade I) and Alexander disease. **Why the correct answer is right:** Rosenthal fibers are elongated, eosinophilic, "corkscrew-shaped" intracellular inclusions found within astrocytic processes. They are primarily composed of **Glial Fibrillary Acidic Protein (GFAP)**, which is the intermediate filament specific to glial cells. These fibers represent a degenerative change or a "clumping" of these filaments, often associated with chronic reactive gliosis or slow-growing tumors. **Analysis of incorrect options:** * **A. Heat shock proteins:** While Rosenthal fibers do contain small amounts of heat shock proteins (specifically **αB-crystallin** and **HSP27**), they are not the primary structural component. GFAP is the definitive protein used for identification in pathology. * **B. Fibrillar proteins:** This is a generic term. While GFAP is a type of intermediate filament (fibrillar in nature), "GFAP" is the specific and correct pathological designation. * **C. Globulins:** These are plasma proteins (like immunoglobulins). They are found in Russell bodies (Plasma cells), not in astrocytic inclusions. **NEET-PG High-Yield Pearls:** 1. **Pilocytic Astrocytoma:** Most common brain tumor in children; typically located in the cerebellum. 2. **Biphasic Pattern:** Histology shows Rosenthal fibers (dense areas) and **Eosinophilic Granular Bodies (EGBs)** (cystic areas). 3. **Alexander Disease:** A rare leukodystrophy characterized by a mutation in the GFAP gene, leading to profuse Rosenthal fiber formation. 4. **Staining:** Rosenthal fibers are strongly eosinophilic on H&E and positive for GFAP on immunohistochemistry.

Q: Which of the following is involved in the pathogenesis of myasthenia gravis?

Autoantibodies against acetylcholine receptors. The hallmark of MG pathogenesis is the production of autoantibodies against the nicotinic acetylcholine receptors (AChR) at the post-synaptic membrane [1]. These antibodies lead to a reduction in the number of functional receptors through three mechanisms: * Complement-mediated damage to the post-synaptic folds [2]. * Increased endocytosis and degradation of receptors (antigenic modulation). * Direct blockade of the ACh binding site. This results in a decreased end-plate potential, failing to trigger muscle fiber action potentials. **2. Why the Other Options are Incorrect:** * **Option A:** Mutations in **ryanodine receptors (RyR1)** are associated with **Malignant Hyperthermia** and Central Core Disease, not MG. * **Option C:** **Synaptobrevin** is a SNARE protein involved in vesicle docking. It is the target of **Tetanus toxin** and **Botulinum toxins (B, D, F, G)**, which prevent neurotransmitter release. * **Option D:** Autoantibodies against **P/Q-type voltage-gated calcium channels (VGCC)** are the cause of **Lambert-Eaton Myasthenic Syndrome (LEMS)** [4]. Unlike MG, LEMS is a presynaptic disorder [4]. **High-Yield Clinical Pearls for NEET-PG:** * **Associated Antibodies:** 85% of patients have anti-AChR antibodies. Of the remaining "seronegative" patients, many have antibodies against **MuSK** (Muscle-Specific Kinase) or **LRP4**. * **Thymus Involvement:** 75% of MG patients have thymus abnormalities (65% hyperplasia, 10% thymoma) [2]. * **Clinical Presentation:** Ptosis and diplopia are the most common initial symptoms (Ocular MG). Weakness typically worsens with activity and improves with rest [3].

Q: Which of the following statements is false with respect to demyelinating disorders?

Involves biochemical abnormality of myelin. To understand this question, one must distinguish between **Demyelinating** and **Dysmyelinating** disorders. ### **Explanation of the Correct Answer** **Option C is false** because demyelinating disorders (like Multiple Sclerosis) involve the **destruction of normally formed myelin** due to inflammation or toxins. The myelin itself is biochemically healthy until it is attacked. In contrast, **Dysmyelinating disorders** (Leukodystrophies) involve a **biochemical abnormality** where myelin is either not formed correctly or is chemically unstable due to genetic enzyme deficiencies. ### **Analysis of Other Options** * **Option A (True):** Increased blood-brain barrier (BBB) permeability is a hallmark of demyelinating diseases [1]. In MS, T-cells cross a "leaky" BBB to attack myelin basic protein, leading to inflammatory plaques. * **Option B (True):** Most autoimmune demyelinating disorders, especially Multiple Sclerosis, show a strong female predilection (typically a 3:1 ratio) [1]. * **Option C (True):** Multiple Sclerosis is indeed the most common primary demyelinating disease of the Central Nervous System (CNS) worldwide. ### **NEET-PG High-Yield Pearls** * **McDonald Criteria:** Used for the diagnosis of MS, focusing on "dissemination in time and space" [1]. * **CSF Findings:** Look for **Oligoclonal bands** (IgG) and an increased IgG index [1]. * **MRI Gold Standard:** Periventricular white matter lesions, specifically **Dawson’s Fingers** (oriented perpendicular to the lateral ventricles) [1]. * **Lhermitte’s Sign:** An electric shock-like sensation down the spine upon neck flexion, common in MS. * **Drug of Choice:** IV Methylprednisolone for acute attacks; Disease-Modifying Therapies (DMTs) like Ocrelizumab or Natalizumab for long-term management.

Question 1

A young child presents with a mass in the posterior cranial fossa exhibiting a mural nodule. What is the most likely diagnosis?

Accepted Answer

Astrocytoma (Pilocytic)

Answer

Hemangiopericytoma

Answer

Ependymoma

Answer

Glioblastoma Multiforme (GBM)

Question 2

The morphologic features of neuronal cell death consist of all EXCEPT:

Accepted Answer

Basophilic inclusions

Answer

Shrinkage of cell body

Answer

Disappearance of Nissl's substance

Answer

Pyknosis of the nucleus

Question 3

A WHO grade I tumour is located in the cerebellum. On histological examination, Rosenthal fibres are seen. What is the most probable diagnosis?

Accepted Answer

Pilocytic astrocytoma

Answer

Medulloblastoma

Answer

Craniopharyngioma

Answer

Ependymoma

Question 4

What is the most common intracranial tumor?

Accepted Answer

Metastatic tumors

Answer

Neuroblastoma

Answer

Schwannoma

Answer

Ependymoma

Question 5

All of the following are true about Medulloblastoma except?

Accepted Answer

It arises from the cerebellum

Answer

It is a small round blue cell tumor

Answer

It is an embryonal tumor

Answer

Chang staging system is used

Question 6

A 50-year-old female presented with left-sided lower limb weakness and mild headaches. Her weakness worsened slowly over the past 5 years. She has a history of cranial irradiation 6 years ago. Her husband has also noted a slight change in her behavior over the past 5 years. Contrast-enhanced MRI showed a sellar/suprasellar space-occupying lesion (SOL). Which of the following is the most common gyri involved and the most common genetic abnormality in the condition suggested by the MRI findings?

Accepted Answer

Anterior paracentral / Deletion 22q

Answer

Posterior paracentral / Deletion 20q

Answer

Anterior paracentral / Deletion 20q

Answer

Posterior paracentral / Deletion 22q

Question 7

What is chromatolysis?

Accepted Answer

Disappearance of Nissl granules

Answer

Disintegration of the nucleus

Answer

Disintegration of the Golgi apparatus

Answer

Decrease in cell size

Question 8

Rosenthal fibers in astrocytoma are composed of which of the following?

Accepted Answer

Glial fibrillary acidic protein (GFAP)

Answer

Heat shock proteins

Answer

Fibrillar proteins

Answer

Globulins

Question 9

Which of the following is involved in the pathogenesis of myasthenia gravis?

Accepted Answer

Autoantibodies against acetylcholine receptors

Answer

Mutation in ryanodine receptors

Answer

Autoantibodies against synaptobrevin

Answer

Autoantibodies against presynaptic calcium channels

Question 10

Which of the following statements is false with respect to demyelinating disorders?

Accepted Answer

Involves biochemical abnormality of myelin

Answer

Increased blood-brain barrier permeability

Answer

More common in females

Answer

Multiple Sclerosis is the most common type of demyelinating disorder

Neuropathology — MCQs

Neuropathology — MCQs

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