Neuropathology — MCQs

A homeless man, who is a chronic alcoholic, is brought to the hospital in a wasted state. He is noted to have a peripheral neuropathy, difficulty balancing, and dementia. He dies suddenly of an arrhythmia, and at autopsy, lesions are found in the mamillary bodies and the vicinity of the third ventricle. What is the vitamin deficiency associated with these signs and symptoms?

Q233Easy

All of the following tumors are malignant except?

Q234Easy

In Alzheimer's disease, what is the characteristic lesion?

Q235Easy

Rosette-shaped arrangement of cells is seen in which of the following conditions?

Q236Easy

Which of the following is a primary neurogenic tumor?

Q237Easy

Death after rupture of a berry aneurysm is most commonly due to?

Q238Easy

What is the most common posterior fossa tumor in children?

Q239Medium

Insult during neuronal migration results in delayed neuronal migration and organization, which can lead to certain disorders. Which of the following is the least likely possibility?

Q240Easy

Which of the following histological patterns is characteristic of Schwannoma?

Neuropathology Indian Medical PG Practice Questions and MCQs

Question 231: A 70-year-old male patient with severe dementia dies. Autopsy demonstrates marked atrophy of the frontal and temporal lobes, with relative sparing of the rest of the brain. Which of the following microscopic features would be most useful in establishing the diagnosis?

A. Enlarged presynaptic axon terminals surrounding a central core of extracellular amyloid-like substance
B. Intracytoplasmic spherules composed of paired helical filaments (Correct Answer)
C. Intracytoplasmic spherules that stain brightly eosinophilic
D. Intranuclear and intracytoplasmic inclusion bodies in enlarged cells

Explanation: **Explanation:** The clinical presentation of a 70-year-old with severe dementia and **circumscribed atrophy** of the frontal and temporal lobes (often called "knife-edge" atrophy) is characteristic of **Pick Disease** (a subtype of Frontotemporal Lobar Degeneration) [1]. **1. Why the Correct Answer is Right:** The hallmark microscopic feature of Pick Disease is the **Pick body**. These are **intracytoplasmic, round, silver-staining (argyrophilic) inclusions**. Ultrastructurally, Pick bodies are composed of **paired helical filaments (PHF)**, straight filaments, and endoplasmic reticulum. These filaments are made of 3R (three-repeat) **Tau protein**. **2. Analysis of Incorrect Options:** * **Option A:** Describes **Neuritic (Senile) Plaques**, which are characteristic of **Alzheimer’s Disease** [2]. While Alzheimer’s causes dementia, it typically presents with generalized atrophy rather than the focal frontotemporal sparing seen here. * **Option C:** Describes **Lewy Bodies**, which are eosinophilic inclusions found in Parkinson’s Disease and Lewy Body Dementia. They are composed of **alpha-synuclein**, not Tau. * **Option D:** Describes the "Owl’s eye" appearance of **Cytomegalovirus (CMV)** inclusions. This is seen in viral encephalitis, not degenerative dementia. **3. High-Yield Clinical Pearls for NEET-PG:** * **Pick Disease vs. Alzheimer’s:** Pick disease presents earlier with **personality changes and aphasia** (frontal/temporal signs) before memory loss. * **Pick Cells:** These are "ballooned" neurons with cleared-out cytoplasm also seen in this condition. * **Tauopathy:** Pick disease is a 3R-Tauopathy, whereas Alzheimer’s involves both 3R and 4R Tau. * **Sparing:** In Pick disease, the posterior two-thirds of the superior temporal gyrus are typically spared [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1294-1295. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 720-721.

Question 232: A homeless man, who is a chronic alcoholic, is brought to the hospital in a wasted state. He is noted to have a peripheral neuropathy, difficulty balancing, and dementia. He dies suddenly of an arrhythmia, and at autopsy, lesions are found in the mamillary bodies and the vicinity of the third ventricle. What is the vitamin deficiency associated with these signs and symptoms?

A. Vitamin B1 (thiamine) (Correct Answer)
B. Vitamin B12
C. Vitamin D
D. Niacin

Explanation: ### Explanation The clinical presentation describes **Wernicke-Korsakoff Syndrome (WKS)**, a neurological complication of chronic alcoholism caused by a deficiency of **Vitamin B1 (Thiamine)**. [1] **1. Why Vitamin B1 is correct:** Thiamine is a critical cofactor for enzymes in glucose metabolism (e.g., pyruvate dehydrogenase, α-ketoglutarate dehydrogenase). In chronic alcoholics, poor diet and impaired absorption lead to thiamine depletion. [1] * **Wernicke Encephalopathy:** Characterized by the triad of **Ophthalmoplegia/Ataxia/Confusion**. * **Korsakoff Syndrome:** Characterized by irreversible **memory loss and confabulation** (dementia-like state). * **Pathology:** The hallmark finding is **hemorrhagic necrosis of the Mamillary Bodies** and the periaqueductal gray matter/walls of the third ventricle. **2. Why other options are incorrect:** * **Vitamin B12:** Deficiency causes **Subacute Combined Degeneration (SCD)** of the spinal cord, affecting the dorsal columns and lateral corticospinal tracts. [2] It does not typically involve the mamillary bodies. [3] * **Vitamin D:** Deficiency leads to Rickets (children) or Osteomalacia (adults), affecting bone mineralization rather than central nervous system structures. * **Niacin (B3):** Deficiency causes **Pellagra**, characterized by the "3 Ds": Dermatitis, Diarrhea, and Dementia. While it causes dementia, it does not present with specific mamillary body lesions or the Wernicke triad. **Clinical Pearls for NEET-PG:** * **High-Yield Triad:** Confusion, Ataxia, and Ophthalmoplegia (Wernicke). * **Imaging:** MRI may show increased signal intensity in the mamillary bodies. * **Management Rule:** Always administer **Thiamine before Glucose** in a suspected alcoholic patient to prevent precipitating Wernicke encephalopathy (glucose oxidation consumes the last remaining thiamine). * **Enzyme Marker:** Erythrocyte transketolase activity is decreased in thiamine deficiency. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 715-716. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 716-717. [3] 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. 130-131.

Question 233: All of the following tumors are malignant except?

A. Glioma
B. Astrocytoma
C. Hemangioblastoma (Correct Answer)
D. Ependymoma

Explanation: **Explanation:** The correct answer is **Hemangioblastoma** because it is a **WHO Grade 1 (benign)** tumor. Unlike the other options, it is a slow-growing, highly vascular neoplasm that does not typically infiltrate the surrounding brain parenchyma. **Why Hemangioblastoma is the correct answer:** Hemangioblastomas are benign tumors most commonly located in the cerebellum [2]. They are often associated with **Von Hippel-Lindau (VHL) syndrome** (autosomal dominant) [1], [2]. Histologically, they are characterized by thin-walled capillaries separated by "stromal cells" with vacuolated, lipid-rich cytoplasm [2]. Because they are Grade 1, they are surgically curable and do not exhibit malignant behavior. **Why the other options are incorrect:** * **Glioma:** This is a broad category of primary CNS tumors (including astrocytomas, oligodendrogliomas, and ependymomas). In neuropathology, almost all gliomas are considered **biologically malignant** because they are locally invasive, lack a true capsule, and have a high tendency for recurrence or progression to higher grades [2], [3]. * **Astrocytoma:** These range from Grade 2 (Diffuse) to Grade 4 (Glioblastoma) [3]. Even low-grade astrocytomas are considered "malignant" in the CNS context because they infiltrate brain tissue, making complete surgical excision nearly impossible [3]. * **Ependymoma:** These are glial tumors arising from the lining of the ventricles or central canal [2], [4]. While they vary in grade (WHO Grade 2 or 3), they are classified as malignant due to their potential for local invasion and "drop metastasis" via cerebrospinal fluid [4]. **High-Yield Clinical Pearls for NEET-PG:** * **VHL Syndrome Triad:** Hemangioblastoma (cerebellum/retina), Renal Cell Carcinoma (clear cell), and Pheochromocytoma. * **Imaging:** Hemangioblastoma typically presents as a **cystic lesion with a brightly enhancing mural nodule** on MRI. * **Marker:** Stromal cells in hemangioblastoma are positive for **Inhibin** (useful for differentiation from RCC). * **Rule of Thumb:** In the CNS, "benign" is a relative term; however, for exam purposes, Hemangioblastoma, Meningioma (Grade 1), and Schwannoma are the classic benign examples. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 724-725. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 726-727. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1312-1313.

Question 234: In Alzheimer's disease, what is the characteristic lesion?

A. Amygdaloid complex
B. Nucleus of Meynert (Correct Answer)
C. Basal ganglia
D. Periventricle

Explanation: **Explanation:** In **Alzheimer’s Disease (AD)**, the most consistent and early neurochemical deficit is a profound loss of **acetylcholine** [1]. The **Nucleus Basalis of Meynert**, located in the basal forebrain, is the primary source of cholinergic innervation to the cerebral cortex. In AD, there is a selective and severe degeneration of neurons in this nucleus, leading to a significant decrease in choline acetyltransferase levels [5]. This cholinergic deficiency is directly linked to the cognitive decline and memory loss characteristic of the disease [1]. **Analysis of Options:** * **Nucleus of Meynert (Correct):** It is the hallmark site of cholinergic neuronal loss in AD. Most pharmacological treatments (Cholinesterase inhibitors like Donepezil) aim to compensate for this specific lesion [1]. * **Amygdaloid complex:** While the amygdala does undergo atrophy and contains neurofibrillary tangles in AD (contributing to emotional symptoms), it is not the primary "characteristic" site of the neurochemical lesion compared to the Nucleus of Meynert. * **Basal ganglia:** These structures (Striatum, Globus Pallidus) are primarily involved in movement disorders like Parkinson’s or Huntington’s disease, rather than the primary pathology of Alzheimer’s. * **Periventricle:** Periventricular lesions (white matter hyperintensities) are more characteristic of Vascular Dementia [1] or Multiple Sclerosis (Dawson’s fingers), not the primary neurodegenerative process of AD. **High-Yield Pearls for NEET-PG:** * **Microscopic Hallmarks:** Extracellular **Amyloid-beta (Aβ) plaques** and intracellular **Tau protein (Neurofibrillary tangles)** [2], [3]. * **Hirano Bodies:** Eosinophilic, rod-like inclusions found in hippocampal pyramidal cells. * **Genetics:** Early-onset is linked to **APP, PSEN1, and PSEN2** mutations; late-onset is associated with the **ApoE4** allele [4]. * **Gross Pathology:** Symmetrical cortical atrophy [2], compensatory **hydrocephalus ex vacuo** [2], and "narrowed gyri with widened sulci." **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 721-722. [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] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1294-1295. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1290-1292. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, p. 1292.

Question 235: Rosette-shaped arrangement of cells is seen in which of the following conditions?

A. Thecoma of ovary
B. Ependymoma (Correct Answer)
C. Neurofibroma
D. Lymphoma

Explanation: **Explanation:** The correct answer is **Ependymoma**. In neuropathology, "rosettes" refer to a circular or spoke-like arrangement of cells around a central point. Ependymomas are characteristically associated with two types of rosette formations [1]: 1. **Perivascular Pseudorosettes:** These are the most common diagnostic feature, where tumor cells are arranged around a central blood vessel, separated by a fibrillary zone (cytoplasmic processes) [1]. 2. **True Ependymal Rosettes:** These are less common but pathognomonic, consisting of cells arranged around a central lumen (mimicking the central canal of the spinal cord) [1]. **Analysis of Incorrect Options:** * **A. Thecoma of ovary:** These are sex cord-stromal tumors composed of spindle-shaped cells with lipid-laden cytoplasm. They do not form rosettes. * **C. Neurofibroma:** These are peripheral nerve sheath tumors characterized by a "shredded carrot" appearance of collagen bundles and spindle cells, not rosette formations. * **D. Lymphoma:** Histologically, lymphomas typically present as sheets of monomorphic, discohesive round cells. **High-Yield Clinical Pearls for NEET-PG:** * **Homer-Wright Rosettes:** These have a central fibrillar core (no lumen/vessel) and are seen in **Medulloblastoma**, Neuroblastoma, and Retinoblastoma. * **Flexner-Wintersteiner Rosettes:** These have a central lumen and are highly specific for **Retinoblastoma** [2]. * **Ependymoma Location:** In children, they most commonly occur in the **fourth ventricle**, often leading to obstructive hydrocephalus. In adults, they are more common in the **spinal cord** (associated with NF2). * **Blepharoplasts:** Electron microscopy of ependymomas may show "blepharoplasts" (basal bodies of cilia). **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 Eye, p. 1342.

Question 236: Which of the following is a primary neurogenic tumor?

A. Meningioma
B. Glioblastoma
C. Acoustic neuroma
D. Neuroblastoma (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Neuroblastoma** **Why it is correct:** A **neurogenic tumor** is one that originates directly from cells of the nervous system (neurons or their precursors). **Neuroblastoma** is an embryonal tumor derived from **primordial neural crest cells** that are destined to form the sympathetic ganglia and adrenal medulla [1]. It is composed of primitive neuroblasts, making it a true "neurogenic" tumor. In pediatric pathology, it is a classic "small round blue cell tumor" and is the most common extracranial solid tumor of childhood [1]. **Why the other options are incorrect:** * **A. Meningioma:** This is a tumor arising from the **meningothelial cells of the arachnoid mater** (the coverings of the brain), not the neural tissue itself [4]. * **B. Glioblastoma:** This is a **glioma**, meaning it originates from **glial cells** (specifically astrocytes), which are the supportive framework of the brain rather than the functional neurons [2]. * **C. Acoustic neuroma:** Despite the name, this is actually a **Schwannoma**. It arises from **Schwann cells** (the myelin-forming cells of the peripheral nervous system), which are considered nerve sheath cells rather than primary neurogenic (neuronal) cells [3], [4]. **High-Yield Clinical Pearls for NEET-PG:** * **Homer-Wright Rosettes:** Characteristically seen in Neuroblastoma (and Medulloblastoma) [1]. * **Biomarkers:** Elevated urinary catecholamines (**VMA and HVA**) are diagnostic hallmarks [1]. * **Genetics:** **N-myc amplification** is the most important poor prognostic indicator. * **Opsoclonus-Myoclonus Syndrome:** A classic paraneoplastic syndrome associated with neuroblastoma ("dancing eyes, dancing feet"). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 483-484. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1313-1314. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1248-1249. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728.

Question 237: Death after rupture of a berry aneurysm is most commonly due to?

A. Subarachnoid hemorrhage (Correct Answer)
B. Subdural hemorrhage
C. Extradural hemorrhage
D. Intraparenchymal hemorrhage

Explanation: **Explanation:** **1. Why Subarachnoid Hemorrhage (SAH) is Correct:** Berry (saccular) aneurysms are thin-walled protrusions that typically develop at the arterial bifurcations of the **Circle of Willis**, most commonly at the junction of the Anterior Communicating Artery [3]. These vessels are located within the **subarachnoid space**. When an aneurysm ruptures, blood is released directly into the cerebrospinal fluid (CSF)-filled space between the arachnoid and pia mater [2]. This is the most common cause of non-traumatic (spontaneous) subarachnoid hemorrhage [1]. **2. Why the Other Options are Incorrect:** * **Subdural Hemorrhage (SDH):** Usually caused by the tearing of **bridging veins** that cross from the cortex to the dural sinuses. It is typically traumatic and occurs between the dura and arachnoid mater. * **Extradural Hemorrhage (EDH):** Most commonly results from trauma to the temple leading to a rupture of the **middle meningeal artery**. It occurs between the skull and the dura mater. * **Intraparenchymal Hemorrhage:** Most commonly caused by **systemic hypertension**, leading to the rupture of Charcot-Bouchard aneurysms in small penetrating arteries (e.g., lenticulostriate arteries) [4]. While a massive SAH can sometimes extend into the brain tissue, it is not the primary site of bleeding for a berry aneurysm. **Clinical Pearls for NEET-PG:** * **Classic Presentation:** "Worst headache of my life" (Thunderclap headache) [1]. * **Risk Factors:** Hypertension, smoking, and genetic conditions like **ADPKD** (Autosomal Dominant Polycystic Kidney Disease) and Ehlers-Danlos Syndrome [1]. * **Diagnosis:** Non-contrast CT is the initial investigation of choice (shows blood in cisterns/sulci). If CT is negative but suspicion is high, **Lumbar Puncture** (showing xanthochromia) is performed. * **Complication:** Vasospasm (usually 3–10 days post-bleed) is a major cause of delayed morbidity; treated with **Nimodipine** [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 705-706. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1272-1273. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, p. 1272. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1270-1272.

Question 238: What is the most common posterior fossa tumor in children?

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

Explanation: **Explanation:** The correct answer is **Astrocytoma**, specifically the **Pilocytic Astrocytoma (Grade I)**. In the pediatric population, approximately 60-70% of brain tumors occur in the **posterior fossa**. While Medulloblastoma is the most common *malignant* brain tumor in children [2], **Pilocytic Astrocytoma** is the most common brain tumor overall in this age group [1] and the most frequent occupant of the posterior fossa. It typically presents as a cystic lesion with a mural nodule in the cerebellum [1]. **Analysis of Options:** * **B. Astrocytoma (Correct):** Specifically Pilocytic Astrocytoma. It is a slow-growing, benign tumor characterized histologically by **Rosenthal fibers** (eosinophilic corkscrew-shaped inclusions) and bipolar cells with long hair-like processes. * **C. Medulloblastoma:** This is the second most common posterior fossa tumor in children. It is a highly malignant primitive neuroectodermal tumor (PNET) arising from the roof of the 4th ventricle [2]. It is characterized by **Homer-Wright rosettes**. * **A. Meningioma:** These are common in adults (usually females) and are typically supratentorial and extra-axial. They are rare in children. * **D. Glioblastoma Multiforme (GBM):** This is the most common primary malignant brain tumor in **adults**, usually located in the cerebral hemispheres (supratentorial) [1], [3]. **NEET-PG High-Yield Pearls:** 1. **Most common pediatric brain tumor:** Pilocytic Astrocytoma [1]. 2. **Most common malignant pediatric brain tumor:** Medulloblastoma [2]. 3. **Imaging hallmark (Pilocytic Astrocytoma):** Cyst with an enhancing mural nodule. 4. **Genetic association:** Pilocytic astrocytomas are frequently associated with **Neurofibromatosis Type 1 (NF1)**. 5. **Marker:** Both Pilocytic Astrocytoma and GBM are **GFAP positive** (glial origin). **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. [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. 1310-1311.

Question 239: Insult during neuronal migration results in delayed neuronal migration and organization, which can lead to certain disorders. Which of the following is the least likely possibility?

A. Polymicrogyria
B. Schizencephaly
C. Lissencephaly
D. Focal cortical dysplasia without balloon cells (Correct Answer)

Explanation: ### Explanation **Core Concept: Neuronal Migration Disorders** During embryogenesis (typically between weeks 12 and 24), neuroblasts migrate from the periventricular germinal matrix to the periphery to form the six-layered cerebral cortex [1]. Insults during this phase (genetic, ischemic, or infectious) lead to **Malformations of Cortical Development (MCD)** [2]. **Why Option D is the Correct Answer:** **Focal Cortical Dysplasia (FCD)**, specifically Type I (without balloon cells), is primarily considered a disorder of **post-migrational cortical organization** or localized proliferation, rather than a global failure of migration. While the neurons reach the cortex, they fail to organize into proper layers. In contrast, FCD Type II (with balloon cells) is often linked to mTOR pathway mutations affecting cell **proliferation**. Among the choices, it is the least representative of a primary "migrational insult." **Analysis of Incorrect Options:** * **Lissencephaly (C):** The classic "smooth brain" disorder. It is a definitive **migration failure** where neurons fail to reach the outer layers, resulting in a thickened 4-layered cortex and absent gyri [2]. * **Schizencephaly (B):** Characterized by gray matter-lined clefts extending from the ventricle to the pial surface. It represents a **trans-mantle migration defect** often due to early vascular insults or *EMX2* mutations. * **Polymicrogyria (A):** Characterized by numerous small, fused gyri. It occurs due to late migrational insults or **post-migrational organizational failure**, but is classically grouped with migration-related spectrum disorders in pathology exams [2]. **NEET-PG High-Yield Pearls:** * **Lissencephaly Type 1:** Associated with *LIS1* gene mutations; presents with "Figure-of-8" appearance on MRI. * **Pachygyria:** Broad, thick gyri (a subset of the lissencephaly spectrum). * **Periventricular Nodular Heterotopia:** Failure of neurons to even start migration; associated with *FLNA* gene (X-linked). * **Balloon Cells:** Pathognomonic for FCD Type IIb and Tuberous Sclerosis; they stain positive for both vimentin and GFAP. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1260-1261. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1258-1260.

Question 240: Which of the following histological patterns is characteristic of Schwannoma?

A. Storiform pattern
B. Spindle cells
C. Antoni A and Antoni B pattern (Correct Answer)
D. Target cells

Explanation: **Explanation:** **Schwannoma** is a benign, encapsulated tumor arising from the Schwann cells of peripheral nerves [1]. The hallmark histological feature is the presence of two distinct patterns: **Antoni A and Antoni B** [1]. 1. **Antoni A (Hypercellular):** This area consists of densely packed spindle cells with elongated nuclei [1]. These cells often form "palisades" (parallel rows) [1]. When two rows of palisading nuclei surround an acellular, eosinophilic area (composed of cytoplasmic processes), it is called a **Verocay body** [1]. 2. **Antoni B (Hypocellular):** This area is loosely organized with a myxoid stroma, fewer cells, and prominent cystic changes or thick-walled blood vessels [1]. **Analysis of Incorrect Options:** * **Option A (Storiform pattern):** This "cartwheel" or whorled arrangement of spindle cells is characteristic of **Dermatofibrosarcoma Protuberans (DFSP)** or Fibrous Histiocytoma, not Schwannoma. * **Option B (Spindle cells):** While Schwannomas are composed of spindle cells, this is a non-specific finding seen in many mesenchymal tumors (e.g., Leiomyoma, Fibroma). Antoni patterns are the *specific* diagnostic feature. * **Option D (Target cells):** Also known as Codocytes, these are associated with hematological conditions like **Thalassemia** or liver disease, and have no relevance to neuropathology. **High-Yield NEET-PG Pearls:** * **S-100 Protein:** Schwannomas show strong, diffuse immunohistochemical staining for S-100. * **Acoustic Neuroma:** The most common location is the CN VIII (vestibulocochlear nerve) at the cerebellopontine angle [2]. * **NF2 Association:** Bilateral acoustic schwannomas are pathognomonic for **Neurofibromatosis Type 2** [2]. * **Differentiation:** Unlike neurofibromas, schwannomas are encapsulated and do not contain axons 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.

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Cellular Pathology of the Nervous System

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Cerebrovascular Diseases

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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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