Neuropathology — MCQs

Neuropathology Indian Medical PG Practice Questions and MCQs

Question 331: What is the primary pathophysiological mechanism of Lambert-Eaton syndrome?

A. IgG antibodies against voltage-gated calcium channels. (Correct Answer)
B. With continuous stimulation, there is a marked decrease in the amplitude of action potentials.
C. There is an increase in the release of presynaptic acetylcholine.
D. IgG antibodies against postsynaptic acetylcholine receptors.

Explanation: ***IgG antibodies against voltage-gated calcium channels*** - **Lambert-Eaton Myasthenic Syndrome (LEMS)** is primarily caused by **autoantibodies (IgG)** targeting the **P/Q-type voltage-gated calcium channels (VGCCs)** on the presynaptic nerve terminals at the neuromuscular junction. - This antibody binding impairs the influx of calcium into the nerve terminal, which is crucial for the release of **acetylcholine (ACh)** into the synaptic cleft. - LEMS is a **paraneoplastic syndrome** in about 50-60% of cases, most commonly associated with **small cell lung cancer (SCLC)**. *IgG antibodies against postsynaptic acetylcholine receptors* - This describes the pathophysiological mechanism of **myasthenia gravis**, not Lambert-Eaton syndrome [1]. - In myasthenia gravis, antibodies target the **nicotinic acetylcholine receptors** on the postsynaptic membrane of the neuromuscular junction [2]. - LEMS affects the **presynaptic** terminal (calcium channels), while myasthenia gravis affects the **postsynaptic** membrane (ACh receptors) [1]. *With continuous stimulation, there is a marked decrease in the amplitude of action potentials* - This description typically refers to **myasthenia gravis**, where repetitive nerve stimulation leads to a **decremental response** (decreasing amplitude) due to reduced acetylcholine receptor availability [1]. - In LEMS, there is often an **incremental response** or facilitation with repetitive stimulation, where muscle action potential amplitude increases, especially after brief exercise or high-frequency stimulation, due to the temporary accumulation of calcium in the presynaptic terminal. *There is an increase in the release of presynaptic acetylcholine* - On the contrary, the primary problem in LEMS is a **decrease** in the presynaptic release of **acetylcholine (ACh)**. - The antibodies targeting VGCCs prevent the necessary calcium influx, thereby hindering the fusion of ACh-containing vesicles with the presynaptic membrane and reducing the amount of ACh released into the synaptic cleft. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1237-1238. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 213-214.

Question 332: Negri bodies are characteristic of which disease?

A. Tetanus
B. Rabies (Correct Answer)
C. Polio
D. AIDS

Explanation: ***Correct: Rabies*** - **Negri bodies** are eosinophilic, sharply outlined cytoplasmic inclusions found in the **pyramidal cells of the hippocampus** and the **Purkinje cells of the cerebellum** of individuals infected with rabies [1]. - Their presence is considered **pathognomonic** for rabies infection and can be detected post-mortem during diagnosis [1]. - These are characteristic intracytoplasmic viral inclusions that are diagnostic of rabies encephalitis. *Incorrect: Tetanus* - Tetanus is caused by the bacterium *Clostridium tetani*, which produces a neurotoxin (tetanospasmin) leading to muscle spasms and rigidity. - It does not involve the formation of distinctive microscopic inclusions like Negri bodies. - Diagnosis is primarily clinical based on characteristic muscle spasms. *Incorrect: Polio* - Polio is a viral disease caused by poliovirus, primarily affecting the anterior horn cells of the spinal cord, leading to muscle weakness and paralysis. - While it causes neural damage, it is not associated with the formation of Negri bodies. - Histologically, poliomyelitis shows neuronal degeneration and inflammation but no specific inclusion bodies. *Incorrect: AIDS* - AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV), which attacks the immune system. - While HIV can affect the central nervous system leading to HIV encephalopathy and various opportunistic infections, it does not produce Negri bodies. - CNS manifestations in AIDS include multinucleated giant cells and microglial nodules, not Negri bodies. **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 333: Which of the following is not seen after nerve transection?

A. Neuroma in continuity (Correct Answer)
B. Myelin ovoids
C. Painful neuroma
D. Morphologic pattern of Wallerian degeneration

Explanation: ***Neuroma in continuity*** - A **neuroma in continuity** occurs when a nerve is injured but remains anatomically intact, meaning there is still some *continuity* of the nerve fibers, albeit scarred or dysfunctional. - In a true **nerve transection**, the nerve is completely severed, making a neuroma in continuity impossible as the nerve ends are no longer connected. *Myelin ovoids* - **Myelin ovoids** are characteristic globular remnants of degraded myelin sheath that form in the distal segment of a transected nerve following **Wallerian degeneration** [2]. - They are a normal and expected finding after nerve transection as the axon and myelin distal to the injury degenerate. *Painful neuroma* - A **painful neuroma**, also known as a stump neuroma, can form at the *proximal* end of a transected nerve [1]. - This occurs due to disorganized growth of regenerating nerve fibers into scar tissue, leading to a tangled mass that can be exquisitely sensitive and painful [1]. *Morphologic pattern of Wallerian degeneration* - **Wallerian degeneration** is the *entire process* of axonal and myelin sheath degeneration that occurs in the distal segment of a nerve fiber after it has been severed from its cell body [2]. - This *morphologic pattern* is the primary response of the distal nerve segment to transection, involving breakdown and phagocytosis of debris [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, p. 1232. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 697-698.

Question 334: Which of the following statements about the pathology in Alzheimer's disease is false?

A. Neuritic Plaques are formed of amyloid protein
B. Number of NFTs correlates with dementia
C. NFTs appear extracellularly before intracellular appearance (Correct Answer)
D. Neurofibrillary tangles (NFT) are made of tau protein

Explanation: ***NFTs appear extracellularly before intracellular appearance*** - This statement is **false** because **neurofibrillary tangles (NFTs)** are **intracellular accumulations** of hyperphosphorylated tau protein [3]. - They develop within neurons before the cell degenerates and releases the tangles into the extracellular space [1], [4]. *Neuritic Plaques are formed of amyloid protein* - **Neuritic plaques** (also known as **amyloid plaques**) are correctly described as being composed primarily of aggregated **amyloid-beta (Aβ) protein** [3]. - These plaques are extracellular deposits found in the brain parenchyma in Alzheimer's disease. *Number of NFTs correlates with dementia* - The **density and distribution of neurofibrillary tangles (NFTs)** in the brain are strongly correlated with the severity of **cognitive decline and dementia** in Alzheimer's disease [2]. - Unlike amyloid plaques, NFTs are considered a better indicator of the clinical progression of the disease [2]. *Neurofibrillary tangles (NFT) are made of tau protein* - **Neurofibrillary tangles (NFTs)** are indeed hallmark lesions in Alzheimer's disease composed of hyperphosphorylated and aggregated strands of **tau protein** [1], [3]. - Tau protein typically stabilizes microtubules within neurons, but in AD, it detaches and forms insoluble aggregates. **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, p. 1292. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 721-722. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1294.

Question 335: Which of the following markers is most commonly associated with neuroblastoma?

A. NMP 22
B. Chromogranin A (Correct Answer)
C. LDH
D. β2 microglobulin

Explanation: ***Chromogranin A*** - **Chromogranin A** is a common **neuroendocrine marker** and is often elevated in neuroblastoma, a neuroendocrine tumor. - Its levels can be used for **diagnosis** and **monitoring treatment response** in patients with neuroblastoma. *NMP 22* - **NMP22 (Nuclear Matrix Protein 22)** is a marker primarily used for the **detection and surveillance of bladder cancer**. - It is not typically associated with neuroblastoma. *LDH* - **LDH (Lactate Dehydrogenase)** is a general marker of **tissue damage or high tumor burden**. [1] - While LDH can be elevated in neuroblastoma due to rapid tumor growth, it is **non-specific** and not the most commonly associated specific marker for this cancer. *β2 microglobulin* - **β2 microglobulin** is a protein found on the surface of most nucleated cells and is elevated in conditions such as **lymphomas**, **multiple myeloma**, and **renal dysfunction**. - It is not considered a primary or specific marker for neuroblastoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, p. 486.

Question 336: What are Gitter cells?

A. Microglia
B. Modified macrophages in the CNS (Correct Answer)
C. Astrocytic cells
D. Oligodendrocytic cells

Explanation: ***Modified macrophages in CNS*** - Gitter cells are **modified macrophages** that have phagocytized lipid and other debris in the central nervous system (CNS), particularly in response to injury or disease [1][2]. - They play a crucial role in **cleaning up cellular debris** and are involved in the inflammatory response within the CNS [2]. *Macroglia* - Macroglia refers to **supportive cells** in the CNS, including astrocytes and oligodendrocytes, rather than being specifically modified macrophages. - It does not specifically describe the **phagocytic role** characteristic of Gitter cells. *Oligodendrocytes* - Oligodendrocytes primarily function to **myelinate axons** in the CNS and do not possess the same phagocytic capabilities as Gitter cells. - They are involved in **insulation** of neuronal axons rather than debris clearance. *Astrocytes* - Astrocytes are the principal **supportive glial cells** in the CNS and do not exhibit the characteristics of Gitter cells. - Their functions include **maintaining blood-brain barrier**, regulating blood flow, and supporting neuronal metabolism, not phagocytosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1255-1256. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 697-698.

Question 337: Which receptors are blocked in Myasthenia Gravis?

A. ACh receptors (Correct Answer)
B. Opioid receptors
C. Na+ receptors
D. Ca++ receptors

Explanation: ***Ach receptors*** - Myasthenia Gravis is an **autoimmune disease** where **antibodies** block, alter, or destroy the **nicotinic acetylcholine receptors** at the **neuromuscular junction** [1], [2]. - This blockage prevents **acetylcholine** from binding to the receptors, leading to impaired muscle contraction and **muscle weakness** [1]. *Ca++ receptors* - **Calcium channels** (not "receptors" in this context) are involved in the release of **acetylcholine** from the presynaptic terminal, but they are not the primary target in Myasthenia Gravis [1]. - While calcium influx is crucial for neurotransmitter release, the problem in Myasthenia Gravis lies postsynaptically, at the **acetylcholine receptor** [2]. *Na+ receptors* - **Sodium channels** are essential for generating and propagating **action potentials** in muscle fibers after acetylcholine binds and opens the acetylcholine receptor. - They are not directly targeted by autoantibodies in Myasthenia Gravis; the issue occurs upstream, preventing the initial depolarization signal [2]. *Opioid receptors* - **Opioid receptors** are involved in pain modulation and other central nervous system functions, primarily binding endorphins and exogenous opioids. - They have no role in the pathophysiology of Myasthenia Gravis, which is a disorder of the **neuromuscular junction** [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 213-214. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1237-1239.

Question 338: Alzheimer type II astrocytes are seen in which condition?

A. Hepatic encephalopathy (Correct Answer)
B. Parkinsonism
C. Alzheimer's
D. Binswanger disease

Explanation: ***Hepatic encephalopathy*** - **Alzheimer type II astrocytes** are characteristic histological findings in cases of **hepatic encephalopathy**, reflecting the brain's response to elevated ammonia levels. - These astrocytes show enlarged, pale nuclei with prominent nucleoli and marginal chromatin, indicating cellular stress from metabolic dysfunction in the setting of liver failure. *Alzheimer's* - Alzheimer's disease is characterized by the presence of **neurofibrillary tangles** (tau protein) and **amyloid plaques** (beta-amyloid protein), not Alzheimer type II astrocytes. - Astrocytes in Alzheimer's disease may show reactive changes, but they do not typically manifest as the specific "Alzheimer type II" morphology. *Parkinsonism* - Parkinsonism is primarily characterized by the degeneration of **dopaminergic neurons** in the substantia nigra and the presence of **Lewy bodies** (alpha-synuclein aggregates). - While glial cells (astrocytes and microglia) do play a role in neuroinflammation in Parkinson's, they do not exhibit the specific Alzheimer type II astrocytic change. *Binswanger disease* - Binswanger disease is a form of **vascular dementia** characterized by diffuse white matter lesions due to chronic ischemia and damage to small cerebral blood vessels. - The pathology primarily involves demyelination and axonal loss in the white matter, with reactive gliosis, but not the specific changes seen in Alzheimer type II astrocytes.

Question 339: Which of the following brain tumors is considered the most aggressive and has the worst prognosis?

A. Glioblastoma Multiforme (Correct Answer)
B. Meningioma
C. Primary CNS lymphoma
D. Anaplastic astrocytoma

Explanation: ***Glioblastoma Multiforme*** - This is a **Grade IV astrocytoma** and is the most common and most aggressive primary brain tumor in adults [1]. - It is characterized by rapid growth, a highly **infiltrative nature**, and poor response to treatment, leading to a very short median survival [1]. *Meningioma* - These are typically **benign (Grade I)** tumors originating from the meninges, accounting for about one-third of all primary brain tumors [2]. - While they can cause symptoms due to mass effect, they usually have a **slow growth rate** and a good prognosis after surgical resection [2]. *Anaplastic astrocytoma* - This is a **Grade III astrocytoma**, which is malignant but generally less aggressive than glioblastoma multiforme (Grade IV) [1]. - It shows **increased cellularity**, nuclear atypia, and mitotic figures, but lacks the microvascular proliferation and necrosis characteristic of glioblastoma [1]. *Primary CNS lymphoma* - This is a **rare non-Hodgkin lymphoma** that primarily affects the brain, spinal cord, or eyes. - While aggressive, it often responds to **chemotherapy** and radiation, making its prognosis generally better than that of glioblastoma, particularly in immunocompetent patients. **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. 1316-1317.

Question 340: Medulloblastoma arises exclusively from the cells of

A. Immature embryonal cells (Correct Answer)
B. Ependymal cells
C. Neurons
D. Spindle-shaped cells

Explanation: ***Immature embryonal cells*** - **Medulloblastoma** is a malignant **embryonal tumor** of the cerebellum, exclusively arising from primitive neuroectodermal cells. - These tumors are thought to originate from remnants of the **external granular layer** of the cerebellum or other primitive neuroectodermal cells. *Ependymal cells* - Tumors arising from **ependymal cells** are called **ependymomas**, which typically occur within the ventricles of the brain or spinal cord. - Ependymomas have distinct histological features and clinical behavior compared to medulloblastomas. *Neurons* - Tumors primarily composed of neurons or with significant neuronal differentiation include **gangliogliomas** and **central neurocytomas**. - **Medulloblastomas** largely consist of undifferentiated, small round cells with minimal evidence of neuronal maturation. *Spindle-shaped cells* - **Spindle-shaped cells** are characteristic of various tumor types, including some **gliomas** (e.g., pilocytic astrocytoma) or mesenchymal tumors. - While some medulloblastoma variants can show desmoplastic features, the hallmark cell type is a small, round, blue embryonal cell.

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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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