Neuropathology — MCQs

Neuropathology Indian Medical PG Practice Questions and MCQs

Question 161: What is the characteristic pathological manifestation in rabies?

A. Ventriculitis
B. Brainstem encephalitis (Correct Answer)
C. Basal ganglia affection
D. Meningitis

Explanation: **Explanation:** Rabies is caused by a neurotropic RNA virus (Lyssavirus) that travels via retrograde axonal transport from the peripheral site of inoculation to the Central Nervous System (CNS) [1]. **Why Brainstem Encephalitis is Correct:** The hallmark of Rabies is a severe, necrotizing **encephalitis** that predominantly involves the **brainstem**, hippocampus, and cerebellum [1]. The virus has a specific predilection for the midbrain and medulla, which correlates clinically with the classic symptoms of hydrophobia and aerophobia (caused by painful spasms of the pharyngeal and respiratory muscles triggered by the brainstem dysfunction). Histologically, the presence of **Negri bodies** (eosinophilic intracytoplasmic inclusions) in the pyramidal cells of the hippocampus and Purkinje cells of the cerebellum is diagnostic [1]. **Why Other Options are Incorrect:** * **Ventriculitis:** This refers to inflammation of the ventricular lining, typically seen in bacterial meningitis or CMV infections, rather than viral neurotropic infections like Rabies. * **Basal Ganglia Affection:** While some viruses (like Japanese Encephalitis) specifically target the basal ganglia and thalamus, Rabies primarily spares these areas in favor of the brainstem and limbic system [1]. * **Meningitis:** Rabies is primarily a parenchymal disease (encephalitis). While mild meningeal irritation may occur, it is not the characteristic or defining pathological manifestation. **NEET-PG High-Yield Pearls:** * **Negri Bodies:** Pathognomonic finding; found in the **cytoplasm** (not nucleus) [1]. * **Incubation Period:** Highly variable; depends on the distance between the bite site and the CNS. * **Clinical Forms:** "Furious" (80%) and "Dumb/Paralytic" (20%). * **Prophylaxis:** Post-exposure prophylaxis (PEP) includes wound cleaning, Rabies vaccine (Days 0, 3, 7, 14, 28), and Rabies Immunoglobulin (RIG). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1279-1280.

Question 162: The morphologic features of neuronal cell death consist of all EXCEPT:

A. Basophilic inclusions (Correct Answer)
B. Shrinkage of cell body
C. Disappearance of Nissl's substance
D. Pyknosis of the nucleus

Explanation: **Explanation:** The question asks for the feature that is **NOT** a characteristic of acute neuronal cell death (often referred to as the "Red Neuron" change). **1. Why "Basophilic Inclusions" is the correct answer:** In acute neuronal injury (due to hypoxia, ischemia, or toxins), the cytoplasm becomes intensely **eosinophilic** (pink), not basophilic. This is due to the loss of RNA (Nissl substance) and the denaturation of intracellular proteins [1]. Basophilic inclusions are typically seen in specific neurodegenerative conditions (e.g., Pick bodies in Pick’s disease) or viral infections (e.g., Negri bodies are eosinophilic, but some viral inclusions can be basophilic), but they are not a general feature of acute neuronal death. **2. Analysis of Incorrect Options:** * **Shrinkage of cell body:** This is a hallmark of neuronal necrosis. As the cell dies and loses its osmotic integrity, it undergoes shrinkage (pyknosis of the cytoplasm). * **Disappearance of Nissl's substance:** Nissl substance represents the Rough Endoplasmic Reticulum (RER). In injury, these organelles undergo dissolution (chromatolysis), leading to the loss of cytoplasmic basophilia and the characteristic "red" appearance [1]. * **Pyknosis of the nucleus:** This refers to nuclear shrinkage and chromatin condensation, which is a standard morphological change in any necrotic cell, including neurons [1]. **Clinical Pearls for NEET-PG:** * **The "Red Neuron":** This is the earliest morphologic marker of irreversible neuronal injury, appearing **12 to 24 hours** after an ischemic insult. * **Key Features:** Intense eosinophilia of cytoplasm, loss of Nissl substance, pyknotic/fragmented nucleus, and loss of the nucleolus [1]. * **Vulnerability:** The most sensitive neurons to hypoxia are the **Pyramidal cells of the Hippocampus (CA1 sector)** and **Purkinje cells of the Cerebellum.** **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 53-55.

Question 163: A WHO grade I tumour is located in the cerebellum. On histological examination, Rosenthal fibres are seen. What is the most probable diagnosis?

A. Medulloblastoma
B. Craniopharyngioma
C. Pilocytic astrocytoma (Correct Answer)
D. Ependymoma

Explanation: ### Explanation **Pilocytic Astrocytoma (PA)** is the most common primary brain tumor in children. The diagnosis in this case is confirmed by the combination of the tumor's location, WHO grade, and characteristic histopathology. **Why Pilocytic Astrocytoma is correct:** * **Location:** It typically arises in the **cerebellum** (infratentorial). * **WHO Grade:** It is a **Grade I** tumor, indicating a relatively benign nature and good prognosis. * **Histology:** It exhibits a "biphasic" pattern (dense fibrillary areas and loose microcystic areas). The pathognomonic finding is **Rosenthal fibers**—thick, elongated, eosinophilic, "corkscrew" shaped inclusions found within astrocytic processes. These represent degraded intermediate filaments (GFAP). **Why the other options are incorrect:** * **Medulloblastoma:** While also located in the cerebellum of children, it is a **WHO Grade IV** tumor [2]. Histologically, it shows small round blue cells and **Homer-Wright rosettes**, not Rosenthal fibers. * **Craniopharyngioma:** This is a suprasellar tumor (near the pituitary), not cerebellar. Histology shows "wet keratin" and "machinery oil" fluid. * **Ependymoma:** Usually arises from the floor of the 4th ventricle [1]. Characterized by **perivascular pseudorosettes** and true ependymal rosettes [1]. **NEET-PG High-Yield Pearls:** * **Imaging:** PA typically appears as a **cystic lesion with an enhancing mural nodule** on MRI. * **Markers:** PA is strongly **GFAP positive**. * **Genetics:** Often associated with **BRAF gene** mutations (KIAA1549-BRAF fusion) or Neurofibromatosis Type 1 (NF1). * **Rosenthal Fibers:** Also seen in Alexander disease and chronic gliosis, but in the context of a pediatric cerebellar tumor, they are diagnostic for PA. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1312-1313. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1314-1315.

Question 164: What is the most common intracranial tumor?

A. Metastatic tumors (Correct Answer)
B. Neuroblastoma
C. Schwannoma
D. Ependymoma

Explanation: **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.

Question 165: All of the following are true about Medulloblastoma except?

A. It arises from the cerebellum (Correct Answer)
B. It is a small round blue cell tumor
C. It is an embryonal tumor
D. Chang staging system is used

Explanation: **Explanation** The correct answer is **A (It arises from the cerebellum)**. While this statement is technically true, in the context of "Except" type questions in pathology, it is often considered the "least specific" or "incorrectly phrased" option if the question implies a more specific origin. Medulloblastoma specifically arises from the **vermis** (in children) or the **cerebellar hemispheres** (in adults). However, if we look at the standard pathology of Medulloblastoma, it is defined as an **embryonal tumor** (Option C) belonging to the **WHO Grade 4** category. **Analysis of Options:** * **Option B (Small round blue cell tumor):** This is a classic histological description. Medulloblastoma consists of densely packed cells with scant cytoplasm and hyperchromatic nuclei, forming "small round blue cells." * **Option C (Embryonal tumor):** Medulloblastoma is the most common malignant embryonal tumor of the central nervous system in children [1]. * **Option D (Chang staging system):** This is the standard staging system used for Medulloblastoma, based on tumor size (T) and metastasis (M), particularly looking for "drop metastases" in the spinal cord [1]. **Note on the Answer Key:** In many competitive exams, if "It arises from the cerebellum" is marked as the "Except" (incorrect) statement, it is usually because the examiner is looking for the specific site of origin: the **External Granular Layer** of the cerebellum. **NEET-PG High-Yield Pearls:** 1. **Homer-Wright Rosettes:** Seen in 40% of cases (pseudorosettes with a central fibrillar core). 2. **Molecular Subtypes:** WNT (best prognosis), SHH, Group 3 (worst prognosis), and Group 4 [1]. 3. **Drop Metastasis:** Characterized by CSF seeding to the cauda equina [1]. 4. **Location:** Most common in the midline (vermis) in children; lateral (hemispheres) in adults. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1314-1315.

Question 166: What is chromatolysis?

A. Disintegration of the nucleus
B. Disintegration of the Golgi apparatus
C. Disappearance of Nissl granules (Correct Answer)
D. Decrease in cell size

Explanation: **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.

Question 167: Which of the following intracranial tumors has the best prognosis?

A. Glioblastoma
B. Cerebellar astrocytoma (Correct Answer)
C. Medulloblastoma
D. Ependymoma

Explanation: ### Explanation The correct answer is **Cerebellar astrocytoma** (specifically the **Pilocytic Astrocytoma** subtype). **1. Why Cerebellar Astrocytoma is correct:** Pilocytic astrocytoma (WHO Grade I) is the most common brain tumor in children and typically arises in the cerebellum. It is characterized by a slow growth rate and is often well-circumscribed, frequently presenting as a cystic lesion with a mural nodule. Because it is Grade I, surgical resection is often curative, giving it the **best prognosis** among all primary neuroepithelial tumors. **2. Why the other options are incorrect:** * **Glioblastoma (GBM):** This is a WHO Grade IV tumor. It is the most common and most aggressive primary malignant brain tumor in adults, with a median survival of only 12–15 months despite treatment [1]. * **Medulloblastoma:** A WHO Grade IV embryonal tumor found in the posterior fossa of children [2]. While it is radiosensitive, it is highly malignant and has a high risk of CSF seeding ("drop metastasis") [2]. * **Ependymoma:** Typically WHO Grade II or III [3]. While less aggressive than GBM, its location (often the floor of the 4th ventricle) makes complete surgical resection difficult, leading to a poorer prognosis compared to Grade I pilocytic astrocytomas [3]. **3. NEET-PG High-Yield Pearls:** * **Hallmark Histology:** Pilocytic astrocytomas show **Rosenthal fibers** (thick, eosinophilic, corkscrew-shaped structures) and bipolar cells with long hair-like processes (piloid cells). * **Genetic Marker:** Often associated with **BRAF gene** alterations (KIAA1549-BRAF fusion). * **Imaging:** Classic appearance is a **large cyst with a brightly enhancing mural nodule** in the cerebellum. * **Grading Tip:** Always remember: Grade I (Pilocytic) > Grade II (Diffuse) > Grade III (Anaplastic) > Grade IV (Glioblastoma). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1310-1311. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1314-1315. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1312-1313.

Question 168: Which protein is primarily involved in Alzheimer's disease?

A. Apolipoprotein E gene
B. Presenilin II
C. Amyloid precursor protein
D. All of the above (Correct Answer)

Explanation: **Explanation:** Alzheimer’s Disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid-beta (Aβ) plaques and tau-related neurofibrillary tangles [3]. The pathogenesis involves a complex interplay of genetic factors that influence the production, aggregation, and clearance of these proteins. * **Amyloid Precursor Protein (APP):** Located on **Chromosome 21**, APP is the parent molecule from which Aβ peptides are cleaved by β and γ-secretases [1]. Mutations in the APP gene lead to increased production of amyloidogenic fragments, directly causing early-onset familial AD [2]. (Note: This explains why Down Syndrome patients develop AD early). * **Presenilin II (PSEN2):** Located on **Chromosome 1**, this protein is a component of the γ-secretase complex. Mutations in PSEN1 (Chr 14) or PSEN2 (Chr 1) alter γ-secretase activity, leading to an increased ratio of the highly toxic Aβ42 peptide [1]. * **Apolipoprotein E (ApoE):** Located on **Chromosome 19**, the **ε4 allele** of ApoE is the most significant genetic risk factor for late-onset sporadic AD. It impairs the clearance of Aβ from the brain interstitium. Since all three proteins play a critical role in the molecular pathology of the disease, **Option D** is the correct answer. **High-Yield NEET-PG Pearls:** * **Most common cause of early-onset AD:** Mutations in **Presenilin 1 (PSEN1)** on Chromosome 14 [1]. * **Protective factor:** The **ApoE ε2** allele is associated with a decreased risk of AD. * **Histology:** Look for **Hirano bodies** (eosinophilic inclusions) and **Granulovacuolar degeneration** in the hippocampus. * **Silver Stains:** Used to visualize Senile (Amyloid) plaques and Neurofibrillary tangles [4]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1290-1292. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 720-721. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 719-720. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 721-722.

Question 169: Ependymomas are commonly associated with which of the following conditions?

A. Tuberous sclerosis
B. Neurofibromatosis 1
C. Neurofibromatosis 2 (Correct Answer)
D. All of the above

Explanation: **Explanation:** **1. Why Neurofibromatosis 2 (NF2) is the correct answer:** Ependymomas are glial tumors arising from the lining of the ventricular system or the central canal of the spinal cord. There is a strong genetic association between **Neurofibromatosis Type 2 (NF2)** and ependymomas, particularly those occurring in the **spinal cord**. The *NF2* gene is located on **chromosome 22q12** and encodes the protein **Merlin** (schwannomin). Mutations or deletions of this gene lead to the development of the "MISME" syndrome (Multiple Inherited Schwannomas, Meningiomas, and Ependymomas) [1]. **2. Why the other options are incorrect:** * **Tuberous Sclerosis (TSC):** This neurocutaneous syndrome is classically associated with **Subependymal Giant Cell Astrocytomas (SEGA)** and cortical tubers, not ependymomas [2]. * **Neurofibromatosis 1 (NF1):** NF1 is primarily associated with **Optic nerve gliomas** (pilocytic astrocytomas), Lisch nodules, and neurofibromas. While both NF1 and NF2 are phakomatoses, their tumor profiles are distinct [2]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** The pathognomonic histological feature of ependymomas is the **Perivascular Pseudorosette** (tumor cells arranged around a central vessel with an intervening fibrillary zone) [3]. True **Ependymal Rosettes** (Flexner-Wintersteiner type) are highly specific but less commonly seen [3]. * **Location by Age:** In children, they typically occur in the **4th ventricle** (often causing obstructive hydrocephalus). In adults, they are most common in the **spinal cord** (frequently associated with NF2). * **Myxopapillary Ependymoma:** A distinct variant found in the **conus medullaris/filum terminale**, characterized by a favorable prognosis [3]. * **Genetic Marker:** Remember the "Rule of 2s" for NF2: Chromosome **22**, Bilateral Acoustic Neuromas (Cranial Nerve **2**), and associated with Ependymomas. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 724-725. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1312-1313.

Question 170: What is the most common tumor in the lateral hemisphere of the brain?

A. Astrocytoma (Correct Answer)
B. Meningioma
C. Ependymoma
D. Medulloblastoma

Explanation: **Explanation:** **Astrocytomas** are the most common primary intra-axial tumors of the central nervous system [1]. In adults, these tumors predominantly occur in the cerebral hemispheres (lateral hemispheres) [1]. They belong to the group of gliomas and range from low-grade (pilocytic astrocytoma) to the highly malignant Glioblastoma Multiforme (GBM), which is the most frequent primary brain malignancy in adults. **Analysis of Options:** * **Meningioma (Option B):** While these are the most common *overall* primary intracranial tumors, they are **extra-axial** (arising from the arachnoid cap cells of the meninges) rather than tumors *in* the brain parenchyma itself. * **Ependymoma (Option C):** These typically arise from the lining of the ventricular system. In children, they are most common in the fourth ventricle (posterior fossa), whereas in adults, they are more frequently found in the spinal cord. * **Medulloblastoma (Option D):** This is a highly malignant embryonal tumor (PNET) that occurs almost exclusively in the **cerebellum** (posterior fossa) of children [1]. It does not typically occur in the lateral cerebral hemispheres. **NEET-PG High-Yield Pearls:** * **Most common primary brain tumor (Overall):** Meningioma. * **Most common primary intra-axial brain tumor:** Astrocytoma (specifically GBM). * **Most common brain tumor (General):** Metastasis (usually multiple, at the grey-white matter junction). * **Rosenthal fibers:** Characteristic of Pilocytic Astrocytoma (Grade I). * **Butterfly Glioma:** Refers to GBM crossing the corpus callosum. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726.

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Cellular Pathology of the Nervous System

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Demyelinating Diseases

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Neurodegenerative Diseases

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CNS Tumors

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Peripheral Nerve Disorders

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Neuromuscular Junction Diseases

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Congenital and Developmental Disorders

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