Neuropathology — MCQs

Neuropathology Indian Medical PG Practice Questions and MCQs

Question 171: In hypoxic damage to the brain, which of the following structures is most vulnerable?

A. Claustrum
B. Mamillary body
C. Layer of corpus callosum
D. Purkinje layer of cerebellum (Correct Answer)

Explanation: **Explanation:** The brain is highly sensitive to hypoxia, but certain regions exhibit **selective vulnerability** due to high metabolic demands and a high density of excitatory neurotransmitter receptors (like NMDA receptors) [1]. **Why Option D is Correct:** The **Purkinje cells of the cerebellum** are among the most sensitive neurons in the entire central nervous system to hypoxic-ischemic insults [1]. Along with the **pyramidal cells of the hippocampus (Sommer sector/CA1)** and the **pyramidal neurons of the neocortex (layers III, V, and VI)**, they are the first to undergo irreversible damage (red neuron formation and subsequent apoptosis) during global ischemia [1]. **Analysis of Incorrect Options:** * **A. Claustrum:** While part of the basal ganglia complex, it does not share the same extreme metabolic vulnerability as the cerebellum or hippocampus. * **B. Mamillary body:** These are characteristically affected in **Wernicke Encephalopathy** (Vitamin B1/Thiamine deficiency), not primarily by acute global hypoxia. * **C. Layer of corpus callosum:** This is white matter. In general, **gray matter** is significantly more vulnerable to hypoxia than white matter because of its higher oxygen consumption and metabolic rate [2]. **NEET-PG High-Yield Pearls:** 1. **Order of Vulnerability:** Hippocampus (CA1) > Purkinje Cells > Neocortex (Layers III, V, VI). 2. **"Red Neurons":** The earliest microscopic change of irreversible hypoxic injury (seen 12–24 hours post-insult), characterized by cytoplasmic eosinophilia and pyknosis [1]. 3. **Watershed Areas:** The region between the ACA and MCA territories is the most common site for "border zone" infarcts during systemic hypotension [2]. 4. **Resistant Areas:** The brainstem nuclei and spinal cord are relatively resistant to hypoxia compared to the cerebrum. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 704-705. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 150-151.

Question 172: Verocay bodies are seen in which of the following tumors?

A. Meningioma
B. Glioma
C. Medulloblastoma
D. Schwannoma (Correct Answer)

Explanation: **Explanation:** **Schwannoma** is the correct answer. These are benign, encapsulated tumors arising from Schwann cells of the cranial or peripheral nerves [1]. Histologically, Schwannomas exhibit a characteristic dimorphic pattern [1]: 1. **Antoni A areas:** Hypercellular regions where spindle-shaped cells form interlacing bundles [1]. 2. **Antoni B areas:** Hypocellular, myxoid regions with loosely arranged cells [1]. **Verocay bodies** are the hallmark of Antoni A areas. They consist of two compact rows of well-aligned nuclei (palisading) separated by an intervening acellular zone composed of cytoplasmic processes [1]. **Why the other options are incorrect:** * **Meningioma:** Characterized by **Psammoma bodies** (laminated calcifications) and whorled patterns of arachnoidal cells [2]. * **Glioma:** Depending on the type, these show different features (e.g., Rosenthal fibers in Pilocytic Astrocytoma or "fried egg" appearance in Oligodendroglioma), but not Verocay bodies. * **Medulloblastoma:** A primitive neuroectodermal tumor (PNET) characterized by small round blue cells and **Homer-Wright rosettes**. **High-Yield Clinical Pearls for NEET-PG:** * **Most common location:** Vestibular branch of the 8th cranial nerve (Acoustic Neuroma) at the cerebellopontine (CP) angle [2]. * **Immunohistochemistry:** Schwannomas are strongly and diffusely **S-100 positive**. * **Genetic Association:** Bilateral acoustic schwannomas are pathognomonic for **Neurofibromatosis Type 2 (NF2)**, involving the *merlin* gene on chromosome 22 [2]. * **Differential:** Unlike Neurofibromas, Schwannomas are encapsulated and do not contain neurites within the tumor mass. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, p. 1250. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728.

Question 173: Which of the following is NOT a sequela of cellular events in atherosclerotic infarction?

A. Neutrophilic infiltration
B. Astrocytes (Correct Answer)
C. Ingress of macrophages
D. Intense eosinophilia

Explanation: In the brain, the cellular response to an atherosclerotic (ischemic) infarction follows a highly specific chronological sequence [1]. The correct answer is **Astrocytes** because, while they are involved in the healing process, they do not disappear; rather, they undergo hypertrophy and hyperplasia. The question likely refers to the fact that neurons and other cells undergo necrosis, but astrocytes are the primary cells responsible for **gliosis** (the CNS equivalent of scarring) [1]. ### Explanation of Options: * **Intense Eosinophilia (Option D):** This is the earliest histological change (12–24 hours), known as **"Red Neurons"** [1]. It occurs due to pyknosis of the nucleus and loss of cytoplasmic RNA. * **Neutrophilic Infiltration (Option A):** Following the acute injury (24–72 hours), neutrophils are the first inflammatory cells to arrive at the site of infarction [1]. * **Ingress of Macrophages (Option C):** From 3 to 7 days, macrophages (derived from microglia and blood monocytes) enter the area to phagocytose myelin and necrotic debris, eventually becoming lipid-laden **"Gitter cells."** * **Astrocytes (Correct Answer):** While astrocytes are present, they do not undergo "liquefaction" or "infiltration" in the same sense as inflammatory cells. Instead, after 1–2 weeks, they undergo **reactive gliosis**, forming a dense network of cytoplasmic processes around the cystic cavity [1]. ### NEET-PG High-Yield Pearls: 1. **Liquefactive Necrosis:** Brain infarction is the classic example of liquefactive necrosis (unlike most organs which undergo coagulative necrosis) [1]. 2. **Timeline:** Red neurons (12-24h) → Neutrophils (24-72h) → Macrophages/Gitter cells (3-7 days) → Gliosis (2 weeks+). 3. **Gitter Cells:** These are specialized macrophages of the CNS that appear "foamy" due to the ingestion of products from broken-down myelin. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1268-1269.

Question 174: Which of the following can cause spinal cord compression?

A. Cysticercosis (Correct Answer)
B. Ankylostomiasis
C. Echinococcus Granulosus
D. Visceral larva migrans

Explanation: **Explanation:** **Cysticercosis** is caused by the larval stage of the tapeworm *Taenia solium* [1]. While it most commonly affects the brain parenchyma (Neurocysticercosis), it can involve the spinal cord in about 1–5% of cases. Spinal cysticercosis can occur in the intramedullary or extramedullary (subarachnoid) space. When these cysts enlarge or trigger an inflammatory response, they act as space-occupying lesions, leading to **spinal cord compression**, myelopathy, or radiculopathy [2]. **Analysis of Incorrect Options:** * **Ankylostomiasis (B):** Caused by hookworms (*Ancylostoma duodenale*), this primarily affects the gastrointestinal tract, leading to iron-deficiency anemia and hypoalbuminemia. It does not involve the central nervous system. * **Echinococcus granulosus (C):** While *Echinococcus* can cause Hydatid disease in the spine (vertebral hydatidosis), it typically involves the bone first, leading to vertebral destruction [1]. While it *can* cause compression, **Cysticercosis** is the more classically tested parasitic cause of direct neural tissue involvement in this context. (Note: If this were a "Multiple Select" question, Echinococcus could be considered, but Cysticercosis is the primary answer in standard pathology texts). * **Visceral Larva Migrans (D):** Caused by *Toxocara canis*, this typically involves the liver, lungs, and eyes (Ocular Larva Migrans). Spinal involvement is extremely rare. **High-Yield Clinical Pearls for NEET-PG:** * **Neurocysticercosis (NCC)** is the most common cause of adult-onset seizures in developing countries. * **Imaging Gold Standard:** MRI is the investigation of choice; look for the "hole-with-a-dot" appearance (the scolex inside the cyst). * **Stages of NCC:** Vesicular → Colloidal vesicular → Granular nodular → Nodular calcified. * **Treatment:** Albendazole or Praziquantel, often administered with steroids to prevent inflammatory edema during larval death. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 403-404. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 702-703.

Question 175: Dumbbell tumors are characteristic of which of the following neoplasms?

A. Meningioma
B. Neurofibroma (Correct Answer)
C. Ependymoma
D. Thymoma

Explanation: ### Explanation **Correct Answer: B. Neurofibroma** **Mechanism and Concept:** A **dumbbell tumor** (or hourglass tumor) refers to a neoplasm that grows through the intervertebral foramen, resulting in a narrow "waist" at the foramen with expansion both inside and outside the spinal canal. This characteristic shape is most commonly associated with **nerve sheath tumors**, specifically **Neurofibromas** and **Schwannomas** [1]. These tumors arise from the spinal nerve roots; as they grow, they follow the path of least resistance through the bony foramen, creating the classic dumbbell appearance on imaging (MRI/CT). **Analysis of Incorrect Options:** * **A. Meningioma:** While these are common intradural extramedullary tumors, they typically arise from the arachnoid cap cells and tend to stay within the spinal canal [2]. They rarely exit through the foramen to form a dumbbell shape. * **C. Ependymoma:** These are **intramedullary** tumors (arising within the spinal cord itself). They cause diffuse cord enlargement rather than foraminal extension. * **D. Thymoma:** These are anterior mediastinal tumors. While they can occasionally invade local structures, they are not associated with the spinal canal or the "dumbbell" radiological sign. **NEET-PG High-Yield Pearls:** * **Most common cause:** While both Schwannomas and Neurofibromas cause dumbbell shapes, **Schwannomas** are statistically the most frequent cause of this radiological sign in the spine. * **Neurofibromatosis Type 1 (NF1):** Multiple neurofibromas are a hallmark [1]. * **Histology:** Look for **Antoni A** (dense cells, Verocay bodies) and **Antoni B** (loose myxoid) patterns in Schwannomas, whereas Neurofibromas show a "shredded carrot" appearance with wavy collagen fibers [1]. * **Differential Diagnosis:** Occasionally, a ganglioneuroma or a lymphoma can present with a similar shape, but nerve sheath tumors remain the primary association for exams. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1248-1250. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728.

Question 176: Negri bodies are characteristically seen in which of the following anatomical locations?

A. Hippocampus (Correct Answer)
B. Hypothalamus
C. Medulla
D. Midbrain

Explanation: ### Explanation **Correct Answer: A. Hippocampus** **Understanding the Concept:** Negri bodies are the pathognomonic histopathological hallmark of **Rabies** (caused by the Lyssavirus) [1]. These are **intracytoplasmic, eosinophilic, round-to-oval inclusion bodies** found in the cytoplasm of neurons. They represent the site of viral replication and consist of viral nucleocapsid proteins. While the Rabies virus affects the entire central nervous system, Negri bodies show a distinct predilection for specific anatomical sites: 1. **Pyramidal cells of the Hippocampus** (specifically the Sommer sector/CA1) [1]. 2. **Purkinje cells of the Cerebellum** [1]. **Analysis of Options:** * **A. Hippocampus:** This is the most characteristic site for finding Negri bodies in humans [1]. Their presence here is diagnostic of Rabies encephalitis. * **B, C, and D (Hypothalamus, Medulla, Midbrain):** While the virus spreads throughout the brainstem and diencephalon causing functional disturbances (like hydrophobia due to brainstem involvement), these areas do not characteristically demonstrate the classic Negri bodies used for histopathological diagnosis [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Negri bodies are sharply outlined, eosinophilic (pink), and often contain internal basophilic granules (inner bodies) [1]. * **Staining:** They are best visualized using **Sellers stain** (a mixture of basic fuchsin and methylene blue) or H&E stain. * **Clinical Correlation:** The absence of Negri bodies does *not* rule out Rabies; they are found in only about 70–80% of cases. * **Transmission:** Retrograde axonal transport via peripheral nerves to the CNS [1]. * **Other Inclusions (Differential):** Do not confuse Negri bodies with **Guarnieri bodies** (Smallpox), **Cowdry Type A** (Herpes Simplex), or **Lewy bodies** (Parkinson’s disease). **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 177: Cowden syndrome is associated with which of the following findings?

A. Medulloblastoma
B. Astrocytoma
C. Dysplastic gangliocytoma (Correct Answer)
D. Primitive neuroectodermal tumor (PNET)

Explanation: **Explanation:** **Cowden Syndrome** (Multiple Hamartoma Syndrome) is an autosomal dominant disorder caused by a mutation in the **PTEN gene** on chromosome 10q23. PTEN is a tumor suppressor gene that inhibits the PI3K/AKT/mTOR pathway. **Why the correct answer is right:** The pathognomonic CNS manifestation of Cowden syndrome is **Lhermitte-Duclos Disease (LDD)**, also known as **Dysplastic Gangliocytoma of the cerebellum**. It is a rare, slowly progressing tumor characterized by the replacement of the internal granular layer of the cerebellum with large, dysplastic ganglion cells. On MRI, it classically presents as a "tiger-striped" cerebellar mass. **Why the incorrect options are wrong:** * **Medulloblastoma:** While associated with familial syndromes like **Gorlin syndrome** (PTCH1 mutation) [1] and **Turcot syndrome** (APC mutation), it is not a feature of Cowden syndrome. * **Astrocytoma:** These are common primary brain tumors but are more typically associated with **Neurofibromatosis type 1 (NF1)** and **Li-Fraumeni syndrome** (TP53). * **PNET:** These aggressive embryonal tumors are not specifically linked to the PTEN mutation or Cowden syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **PTEN Hamartoma Tumor Syndrome (PHTS):** Includes Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome. * **Associated Malignancies:** Patients have a significantly increased risk of **Breast cancer** (most common), **Follicular Thyroid cancer**, and **Endometrial cancer**. * **Mucocutaneous findings:** Trichilemmomas (benign hair follicle tumors) and oral papillomas are hallmark diagnostic features. * **Lhermitte-Duclos Disease** is now considered a Grade I WHO tumor and is often the first clinical sign leading to a Cowden syndrome diagnosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 306-307.

Question 178: Which type of glial cell is commonly found to be malfunctioning in Alzheimer's disease?

A. Microglia (Correct Answer)
B. Radial glia
C. Dendrites
D. Oligodendrocytes

Explanation: **Explanation:** **Microglia** are the resident macrophages of the Central Nervous System (CNS). In Alzheimer’s Disease (AD), microglia play a dual, complex role. Initially, they act as scavengers to clear **Amyloid-beta (Aβ) plaques** [1]. However, as the disease progresses, chronic overactivation leads to "microglial dysfunction" or senescence [2]. These dysfunctional cells fail to clear debris and instead release pro-inflammatory cytokines (IL-1, IL-6, TNF-α), contributing to chronic neuroinflammation and progressive neuronal death. **Analysis of Incorrect Options:** * **Radial glia:** These are bipolar cells that serve as primary progenitors during embryonic development and act as a scaffold for migrating neurons. They are not the primary glial cells implicated in AD pathogenesis. * **Dendrites:** These are not glial cells; they are branched extensions of **neurons** that receive signals. While dendritic spine loss occurs in AD, the question specifically asks for a type of *glial cell*. * **Oligodendrocytes:** These cells are responsible for myelination in the CNS. While myelin loss can occur secondary to neuronal death in AD, they are not the central drivers of the inflammatory pathology characteristic of the disease. **High-Yield Clinical Pearls for NEET-PG:** * **Astrocyte involvement:** While not an option here, **Astrocytes** also malfunction in AD, forming a "glial scar" around plaques (astrogliosis) [2]. * **Histopathology of AD:** Look for extracellular **Amyloid-beta plaques** (derived from APP) and intracellular **Neurofibrillary tangles** (composed of hyperphosphorylated **Tau protein**) [3]. * **Hirano Bodies:** Eosinophilic, actin-rich inclusions found in the hippocampus of AD patients. * **Genetics:** Early-onset AD is associated with mutations in **Presenilin 1 (PSEN1)**, Presenilin 2, and APP [1]. Late-onset is associated with the **ApoE-ε4** allele. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 719-721. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1294-1295. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1293.

Question 179: Shearing damage is seen in which of the following organs?

A. Heart
B. Liver
C. Brain (Correct Answer)
D. Spinal cord

Explanation: **Explanation:** The correct answer is **Brain**. This question refers to the mechanism of **Diffuse Axonal Injury (DAI)**, a common and severe form of traumatic brain injury. **1. Why Brain is Correct:** Shearing damage occurs due to **rotational acceleration or deceleration** forces [2]. The brain consists of tissues with different densities (gray matter vs. white matter). When the head undergoes sudden rotation, these layers move at different speeds, creating a "sliding" or shearing effect at the interface [1]. This mechanical force stretches and tears the axons, leading to DAI. It is most commonly seen at the **corticomedullary (gray-white matter) junction**, corpus callosum, and brainstem. **2. Why Incorrect Options are Wrong:** * **Heart and Liver:** These are solid visceral organs. While they can suffer from blunt trauma, lacerations, or rupture, they do not possess the specific structural interface (like the gray-white matter junction) or the suspension within a fluid-filled cavity (CSF) that predisposes them to rotational shearing forces. * **Spinal Cord:** While the spinal cord can suffer from traction or compression, "shearing damage" as a specific pathological entity is a hallmark of intracranial injury due to the brain's ability to rotate within the skull. **3. NEET-PG High-Yield Pearls:** * **Microscopic Hallmark:** The presence of **Axonal Swellings (Retraction Bulbs)** [1]. These are eosinophilic masses of cytoplasm where axonal transport has been interrupted. * **Staining:** Silver stains or immunohistochemistry for **Beta-Amyloid Precursor Protein (B-APP)** or **Ubiquitin** are used to highlight damaged axons. * **Clinical Presentation:** Patients often present with immediate, persistent post-traumatic coma or a vegetative state, even when CT scans appear relatively normal (disproportionate clinical severity to imaging). * **Most common site:** Gray-white matter junction of the cerebral hemispheres [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1261-1264. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1261-1262.

Question 180: Neurofibrillary tangles and amyloid plaques are characteristic features of which condition?

A. Alzheimer's disease (Correct Answer)
B. Creutzfeldt-Jakob disease (CJD)
C. Hepatic encephalopathy
D. Parkinsonism

Explanation: **Explanation:** **Alzheimer’s Disease (AD)** is the most common cause of dementia in the elderly. Its definitive diagnosis relies on the presence of two hallmark microscopic lesions: [1], [3] 1. **Amyloid Plaques (Neuritic Plaques):** These are extracellular deposits of **Aβ-amyloid** (derived from Amyloid Precursor Protein). They stain with **Congo Red** (showing apple-green birefringence) and are found in the neuropil. [1], [3] 2. **Neurofibrillary Tangles (NFTs):** These are intracellular bundles of filaments composed of hyperphosphorylated **Tau protein**. They appear as flame-shaped structures within the cytoplasm of neurons. [1], [3] **Why the other options are incorrect:** * **Creutzfeldt-Jakob disease (CJD):** Characterized by **spongiform encephalopathy** (vacuolation of the neuropil) and PrPSc prion protein accumulation, but lacks classic plaques and tangles. * **Hepatic encephalopathy:** Characterized by the presence of **Alzheimer Type II astrocytes** (enlarged nuclei with pale chromatin) in the cortex and basal ganglia, caused by hyperammonemia. * **Parkinsonism:** The hallmark is the **Lewy body**, which is an intracytoplasmic, eosinophilic inclusion made of **̑-synuclein**. **High-Yield Clinical Pearls for NEET-PG:** * **Hirano bodies** (actin-rich eosinophilic inclusions) are also seen in Alzheimer’s. [1] * The **ApoE ̕4 allele** increases the risk of AD, while **ApoE ̕2** is protective. * Amyloid in AD is specifically **A̢42**, which is highly prone to aggregation. * Grossly, AD shows **cortical atrophy** with "narrowed gyri and widened sulci," most prominent in the hippocampus and temporal lobes. [2] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1293. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1294. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 721-722.

Practice by Chapter

Cellular Pathology of the Nervous System

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Cerebrovascular Diseases

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Trauma to the Central Nervous System

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Infections 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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