Neuropathology — MCQs

Neuropathology Indian Medical PG Practice Questions and MCQs

Question 321: Which of the following is a pathognomonic feature of Alzheimer's disease?

A. Plaques and tangles (Correct Answer)
B. Presence of Lewy bodies
C. Presence of Pick bodies
D. Red neuronal degeneration

Explanation: ***Plaques and tangles*** - The presence of **amyloid plaques** (extracellular deposits of beta-amyloid protein) and **neurofibrillary tangles** (intracellular aggregates of hyperphosphorylated tau protein) are the defining neuropathological hallmarks of Alzheimer's disease [1]. These are considered **pathognomonic** features upon post-mortem examination. - While other neurological conditions can have some tauopathy or amyloid deposition, the specific combination, distribution, and extensive nature of these two pathologies are unique to Alzheimer's [1]. [3] *Presence of Lewy bodies* - **Lewy bodies** are abnormal aggregates of alpha-synuclein protein that are characteristic of **Parkinson's disease** and **Lewy body dementia** [3]. - Their presence indicates a distinct neurodegenerative process, separate from Alzheimer's disease. *Presence of Pick bodies* - **Pick bodies** are cytoplasmic inclusions composed primarily of tau protein, but they are characteristic of **Pick's disease**, a type of frontotemporal dementia [2]. - Pick's disease has a different clinical presentation and neuropathological profile than Alzheimer's disease [2]. *Red neuronal degeneration (general feature)* - **Red neuronal degeneration** refers to the morphological changes seen in neurons undergoing acute irreversible ischemic injury, such as during a **stroke**. - It is a general feature of acute neuronal death and is not specific to, nor a pathognomonic feature of, Alzheimer's disease. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1294. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1294-1295. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 721-722.

Question 322: Which nerve biopsy is taken to diagnose neuritic leprosy?

A. Radial cutaneous nerve (Correct Answer)
B. Median nerve
C. Radial nerve
D. Ulnar nerve

Explanation: ***Radial cutaneous nerve*** - The **radial cutaneous nerve** (superficial branch of radial nerve) is the **preferred nerve for biopsy** in suspected neuritic leprosy - It is a **purely sensory nerve** with minimal functional consequences if damaged, making it the safest choice for diagnostic biopsy - This nerve is **superficially located** at the wrist and easily accessible for biopsy procedures - Provides excellent diagnostic yield as it is commonly involved in leprosy neuritis *Ulnar nerve* - While the ulnar nerve is frequently **thickened and tender** in leprosy and can be easily palpated, it is **NOT preferred for biopsy** [1] - Contains both **motor and sensory fibers**, so biopsy carries significant risk of functional impairment including weakness of intrinsic hand muscles - Clinical examination and nerve thickening is sufficient for diagnosis; biopsy is avoided due to morbidity risk *Median nerve* - The median nerve can be affected in leprosy but is **not suitable for biopsy** due to its critical motor and sensory functions - Biopsy would risk severe hand dysfunction including loss of thumb opposition and sensory loss in the lateral palm - Deep location also makes it less accessible compared to superficial cutaneous nerves *Radial nerve* - The **main radial nerve trunk** is a mixed nerve with important motor functions (wrist and finger extension) - Its deep location and functional importance make it **unsuitable for diagnostic biopsy** - Risk of wrist drop and significant morbidity makes this an inappropriate biopsy site **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 386.

Question 323: Which mutation is characteristic of oligodendroglioma?

A. BRAF V600E
B. IDH1 mutation alone
C. EGFR amplification
D. 1p19q codeletion (Correct Answer)

Explanation: ***1p19q codeletion*** - The **codeletion of chromosomal arms 1p and 19q** is a molecular hallmark of oligodendroglioma and is crucial for diagnosis according to WHO classification [1]. - This specific genetic alteration is associated with **better prognosis** and increased responsiveness to chemotherapy and radiation in patients with oligodendroglioma. *BRAF V600E* - The **BRAF V600E mutation** is commonly found in **pleomorphic xanthoastrocytoma (PXA)** and **ganglioglioma**, but not typically in oligodendroglioma. - It is also characteristic of other cancers like **melanoma** and some **thyroid cancers**. *IDH1 mutation alone* - While an **IDH1 mutation** is present in most oligodendrogliomas, it is usually accompanied by the **1p19q codeletion** [1]. Isolated IDH1 mutation without 1p19q codeletion suggests other diffuse gliomas, such as astrocytoma. - An isolated IDH1 mutation is more characteristic of **IDH-mutant astrocytoma**, especially when 1p19q is intact. *EGFR amplification* - **EGFR amplification** is a classic genetic alteration found in **glioblastoma (GBM)**, a highly aggressive primary brain tumor [2]. - It is rarely seen in oligodendrogliomas and is associated with a **worse prognosis** in GBM. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1311-1312. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1308-1310.

Question 324: What is the primary pathological mechanism in classical Guillain-Barré syndrome affecting the peripheral nervous system?

A. It blocks neurotransmitter release.
B. It causes demyelination of peripheral nerves. (Correct Answer)
C. It inhibits muscle contraction.
D. It leads to axonal degeneration.

Explanation: ***It causes demyelination of peripheral nerves.*** - Classical Guillain-Barré syndrome (AIDP - Acute Inflammatory Demyelinating Polyneuropathy) is an autoimmune disorder where the immune system attacks the **myelin sheath** surrounding peripheral nerves. - This **demyelination** impairs nerve signal conduction, leading to weakness and paralysis. - AIDP represents the most common form of GBS in Western countries (~85-90% of cases). *It blocks neurotransmitter release.* - Conditions like **Lambert-Eaton myasthenic syndrome** primarily involve antibodies targeting presynaptic voltage-gated calcium channels, thereby reducing neurotransmitter release. - While GBS affects nerve conduction, its primary mechanism is not the blockage of neurotransmitter release at the synapse. *It inhibits muscle contraction.* - Inhibition of muscle contraction is a downstream effect of impaired nerve innervation, but the fundamental problem in GBS is with the **nerve itself**, not the muscle's ability to contract directly. - Conditions like **myasthenia gravis** directly affect neuromuscular transmission by blocking acetylcholine receptors on muscle fibers. *It leads to axonal degeneration.* - While **axonal variants** of GBS exist (AMAN - Acute Motor Axonal Neuropathy; AMSAN - Acute Motor-Sensory Axonal Neuropathy), particularly common in Asia, the **classical and most common form** is characterized by **primary demyelination** (AIDP). - Pure axonal degeneration as a primary pathology is seen in specific GBS variants, not the classical presentation. - Secondary axonal damage can occur in severe or prolonged cases.

Question 325: In which type of cells are Negri bodies, characteristic of rabies virus infection, most commonly found?

A. Neurons (Correct Answer)
B. Hepatocytes
C. Epithelial cells
D. Cardiomyocytes

Explanation: ***Neurons*** - **Negri bodies** are eosinophilic, sharply demarcated **intracytoplasmic inclusions** found in the cytoplasm of neurons, particularly in the **hippocampus** (Ammon's horn) and **Purkinje cells** of the cerebellum [1]. - Their presence is **pathognomonic** for **rabies virus infection**, indicating viral replication within these nerve cells [1]. *Hepatocytes* - Hepatocytes are liver cells and are not the primary site for rabies virus replication or the formation of Negri bodies. - While some viruses infect hepatocytes, rabies primarily targets the **central nervous system**. *Epithelial cells* - Epithelial cells form linings and coverings throughout the body, but they are not the primary host cells for rabies virus replication. - Rabies virus directly impacts the **nervous system**, not epithelial tissues. *Cardiomyocytes* - Cardiomyocytes are muscle cells of the heart and are not typically infected by the rabies virus. - Rabies is a **neurotropic virus**, meaning it specifically targets neuronal tissue. **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 326: Which of the following is a pathological characteristic of Alzheimer's disease?

A. Plaques and tangles (Correct Answer)
B. Gradual cognitive decline
C. Increased reflexes
D. Subcortical atrophy

Explanation: ***Plaques and tangles*** - The hallmark pathological features of **Alzheimer's disease** are extracellular **amyloid-beta plaques** and intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein [1], [2]. - These accumulations lead to neuronal dysfunction and death, causing the characteristic symptoms of the disease [1]. *Increased reflexes* - **Increased reflexes** (hyperreflexia) are not a characteristic pathological feature of Alzheimer's disease; they are more commonly seen in conditions affecting upper motor neurons, such as **stroke** or **multiple sclerosis**. - Alzheimer's primarily affects cognitive function and does not typically present with significant motor system abnormalities in its early stages. *Gradual cognitive decline* - **Gradual cognitive decline** is a *clinical symptom* of Alzheimer's disease, not a pathological characteristic [1]. - It describes the functional manifestation of the underlying neuropathology rather than the specific tissue changes. *Subcortical atrophy* - Alzheimer's disease predominantly causes **cortical atrophy**, particularly affecting the hippocampus, temporal lobes, and parietal lobes, rather than primarily subcortical structures [2]. - While brain atrophy occurs, the most characteristic and specific pathological changes at the microscopic level are the **plaques and tangles**, which are the definitive diagnostic features on histopathology [1], [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1294. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 720-722.

Question 327: A 70-year-old male presents with progressive memory loss, visual hallucinations, and parkinsonism. Which neuropathological finding is most characteristic of his condition?

A. Neurofibrillary Tangles
B. Lewy Bodies (Correct Answer)
C. Amyloid Plaques
D. Pick Bodies

Explanation: ***Lewy Bodies*** [1] - The presence of **visual hallucinations**, **memory loss**, and **parkinsonism** points towards Lewy body dementia, which is characterized by the presence of these abnormal aggregates [1]. - **Lewy bodies** contain the protein **alpha-synuclein**, which is linked to the pathophysiology of both Parkinson's disease and dementia with Lewy bodies [1][2]. *Neurofibrillary Tangles* - Typically associated with **Alzheimer's disease**, they represent **tau protein** abnormalities rather than the symptoms presented. - Do not account for the **visual hallucinations** or the combination of symptoms seen in this patient. *Pick Bodies* - Associated with **Frontotemporal lobar degeneration**, these are not related to the **parkinsonian features** or hallucinations described. - Characterized by changes in personality and social behavior, which differ from the clinical picture here. *Amyloid Plaques* - Primarily found in **Alzheimer's disease**, which does not typically present with visual hallucinations or parkinsonism. - Amyloid plaques are related to cognitive impairment, but not the combination of symptoms in this case. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1297-1298. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1296-1297.

Question 328: A 60-year-old man presents with memory loss, difficulty performing daily activities, and visuospatial disorientation. Which protein accumulation is characteristic of the most likely diagnosis?

A. Beta-amyloid (Correct Answer)
B. Tau protein
C. Alpha-synuclein protein
D. Prion proteins

Explanation: ***Beta-amyloid*** - The symptoms of memory loss, difficulty performing daily activities, and visuospatial disorientation are highly suggestive of **Alzheimer's disease**. [1] - **Beta-amyloid plaques** (extracellular) and **neurofibrillary tangles** (intracellular tau) are the two hallmark pathological features of Alzheimer's disease. [1], [2] - Beta-amyloid accumulation is considered the most **characteristic** finding, as it is relatively specific to Alzheimer's disease, whereas tau pathology can occur in various neurodegenerative conditions. [1] *Tau protein* - While **hyperphosphorylated tau protein** forms **neurofibrillary tangles**, which are equally important in Alzheimer's disease pathology, tau accumulation is **less specific** as it occurs in multiple tauopathies. [1] - Other tauopathies include frontotemporal dementia, progressive supranuclear palsy, and corticobasal degeneration, which present with different clinical profiles. - Both amyloid and tau pathology contribute to neurodegeneration in Alzheimer's disease. *Alpha-synuclein protein* - Accumulation of **alpha-synuclein protein** is characteristic of **Parkinson's disease** and **Lewy body dementia** (LBD). [2] - LBD commonly involves fluctuating cognition, visual hallucinations, and Parkinsonism, which differ from the typical Alzheimer's presentation. *Prion proteins* - **Prion diseases** (e.g., Creutzfeldt-Jakob disease) are characterized by misfolded **prion proteins**, leading to rapidly progressive dementia. - The clinical presentation typically involves a much more rapid decline (weeks to months) and additional neurological signs such as myoclonus and ataxia. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1290-1294. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 719-722.

Question 329: Which of the following best describes the pathophysiology of migraine?

A. Migraines result from purely vascular constriction without neurogenic involvement.
B. Migraines involve vasodilation and neurogenic inflammation. (Correct Answer)
C. Migraines are caused by cortical spreading depression alone without vascular changes.
D. Migraines are caused by primary vasoconstriction leading to cerebral ischemia.

Explanation: Migraines involve vasodilation and neurogenic inflammation [1]. - The activation and sensitization of the **trigeminovascular system** lead to the release of neuropeptides like **calcitonin gene-related peptide (CGRP)**, substance P, and neurokinin A [2]. - This release causes **vasodilation** of intracranial blood vessels and extravasation of plasma proteins, resulting in **neurogenic inflammation** observed in migraine [1], [2]. *Migraines result from purely vascular constriction without neurogenic involvement.* - While initial theories focused on vasoconstriction, current understanding emphasizes a complex interplay of **neurovascular changes**, including subsequent vasodilation [1]. - **Neurogenic inflammation** is a key component, indicating that migraines are not solely a vascular phenomenon [2]. *Migraines are caused by primary vasoconstriction leading to cerebral ischemia.* - This represents an **outdated theory** from the early-to-mid 20th century that proposed migraines were due to vasoconstriction causing cerebral ischemia. - Modern understanding shows that while vasoconstriction may occur in the **aura phase**, the headache phase involves **vasodilation and neurogenic inflammation** via the trigeminovascular system, not ischemia [1], [2]. *Migraines are caused by cortical spreading depression alone without vascular changes.* - **Cortical spreading depression (CSD)** is a wave of neuronal and glial depolarization that propagates across the cerebral cortex and is strongly implicated in migraine aura. - However, CSD is thought to **activate the trigeminovascular system**, leading to the subsequent vascular and inflammatory changes characteristic of the migraine headache phase, meaning it is not an isolated event [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 694-695. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 100-101.

Question 330: Which of the following statements is MOST accurate regarding Huntington's disease?

A. There is a loss of function type of mutation
B. It is an autosomal recessive
C. It is a trinucleotide repeat expansion type of disorder
D. It is caused by an increased number of CAG repeats in the HTT gene. (Correct Answer)

Explanation: ***It is caused by an increased number of CAG repeats in the HTT gene.*** - Huntington's disease is characterized by a **trinucleotide repeat expansion** specifically involving the **CAG** (cytosine-adenine-guanine) sequence within the *HTT* gene [1]. - An increase above a certain threshold (typically >35-40 CAG repeats) leads to the production of an abnormally long **huntingtin protein**, causing neuronal dysfunction and degeneration [1]. - This is the **most specific and accurate** statement among the options provided. *There is a loss of function type of mutation* - Huntington's disease is primarily a **gain-of-function** disorder, where the expanded polyglutamine tract confers novel, toxic properties to the huntingtin protein, rather than the loss of its normal function [1]. - The mutant protein forms **aggregates** that disrupt various cellular processes, leading to neuronal damage [1]. *It is an autosomal recessive* - Huntington's disease is an **autosomal dominant** disorder [2], meaning only one copy of the mutated *HTT* gene is sufficient to cause the disease. - This inheritance pattern leads to a 50% chance of an affected parent passing the disease to each child. *It is a trinucleotide repeat expansion type of disorder* - While technically **true** and characteristic of Huntington's disease, this statement is **less specific** than mentioning the **CAG repeats** in the *HTT* gene [1]. - Other trinucleotide repeat expansion disorders exist (e.g., Fragile X syndrome with CGG repeats, myotonic dystrophy with CTG repeats), making the more specific option identifying CAG repeats in HTT the **most accurate** descriptor for this comparative question [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 177-179. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 149-150.

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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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