Neuropathology — MCQs
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Brain space-occupying lesions cause death by what mechanism?
A 35-year-old man develops hemiparesis, ataxia, homonymous hemianopia, and cognitive deterioration. An MRI of the brain demonstrates widespread areas of abnormal T2 signal in the white matter. An electroencephalogram is remarkable for diffuse slowing over both cerebral hemispheres. Brain biopsy reveals demyelination with abnormal giant oligodendrocytes, some of which contain eosinophilic inclusions. This patient's condition is most closely related to which of the following diseases?
All of the following are true about Arnold-Chiari malformation except:
Which of the following conditions is characterized by the presence of Lewy bodies?
Which of the following brain tumors arises from arachnoid villi?
Which of the following brain tumors does not spread via CSF?
Craniopharyngiomas are basically?
In tuberculous meningitis, where do the exudates tend to be most severe?
A 40-year-old woman presents with severe headaches and dizziness. An MRI reveals a brain tumor, and a biopsy confirms it as a melanoma. She dies 2 months later. Pigmented lesions are not seen on her skin or scalp at the time of diagnosis or during postmortem examination. Which of the following is the most likely source of the malignant melanoma cells?
Misfolded amyloid deposition in the brain is seen in which of the following conditions?
Neuropathology Indian Medical PG Practice Questions and MCQs
Question 181: Brain space-occupying lesions cause death by what mechanism?
- A. Acute hypertension
- B. Brain herniation (Correct Answer)
- C. Cushing syndrome
- D. Hypotension
Explanation: ### Explanation **Correct Answer: B. Brain Herniation** The skull is a rigid, non-expandable compartment containing brain tissue, blood, and cerebrospinal fluid (CSF). According to the **Monro-Kellie doctrine**, any increase in the volume of one component (e.g., a space-occupying lesion like a tumor, abscess, or hematoma) must be compensated by a decrease in the others [1]. Once compensatory mechanisms are exhausted, intracranial pressure (ICP) rises sharply [1]. The brain tissue is then forced (herniated) from a compartment of high pressure to one of lower pressure across rigid dural folds (like the falx cerebri or tentorium cerebelli) or through the foramen magnum [1]. **Transtentorial (uncal) herniation** can compress the midbrain, while **tonsillar herniation** compresses the medulla oblongata [3]. This leads to the compression of vital cardiorespiratory centers, resulting in respiratory arrest and death [3]. **Why other options are incorrect:** * **A & D (Hypertension/Hypotension):** While systemic blood pressure changes occur as a physiological response to increased ICP, they are secondary effects. Death is not caused by the blood pressure level itself, but by the mechanical compression of the brainstem. * **C (Cushing Syndrome):** This is a hormonal disorder caused by excess cortisol. It is often confused with the **Cushing Triad** (hypertension, bradycardia, and irregular respiration), which is a clinical sign of increased ICP, but not the primary mechanism of death [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Cushing Triad:** Hypertension, Bradycardia, and Abnormal Respirations (indicates imminent herniation). * **Duret Hemorrhages:** Small linear hemorrhages in the midbrain and pons caused by the downward displacement of the brainstem during herniation [3]. * **Kernohan’s Notch:** A false localizing sign where the contralateral cerebral peduncle is compressed against the tentorium, causing hemiparesis on the same side as the lesion. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 699-700. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 698-699. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1257-1258.
Question 182: A 35-year-old man develops hemiparesis, ataxia, homonymous hemianopia, and cognitive deterioration. An MRI of the brain demonstrates widespread areas of abnormal T2 signal in the white matter. An electroencephalogram is remarkable for diffuse slowing over both cerebral hemispheres. Brain biopsy reveals demyelination with abnormal giant oligodendrocytes, some of which contain eosinophilic inclusions. This patient's condition is most closely related to which of the following diseases?
- A. AIDS (Correct Answer)
- B. Chickenpox
- C. Measles
- D. Syphilis
Explanation: The clinical presentation and histopathology described point to a diagnosis of **Progressive Multifocal Leukoencephalopathy (PML)**. ### **Explanation of the Correct Answer** PML is a demyelinating disease caused by the reactivation of the **JC virus** (a polyomavirus) [1]. The virus selectively infects and destroys **oligodendrocytes**, the myelin-producing cells of the CNS [1]. * **Histopathology:** The pathognomonic findings are **"ground-glass" intranuclear viral inclusions** within enlarged, bizarre-looking **giant oligodendrocytes** and reactive, "monstrous" astrocytes [1]. * **Association:** PML occurs almost exclusively in severely immunocompromised individuals [1]. **AIDS** is the most common underlying condition (seen in up to 5% of AIDS patients), though it can also occur in patients with leukemia, lymphoma, or those on immunosuppressants (e.g., Natalizumab) [1]. ### **Why Other Options are Incorrect** * **B. Chickenpox (VZV):** Can cause encephalitis or post-infectious cerebellar ataxia, but does not typically present with the specific "giant oligodendrocyte" pathology of PML. * **C. Measles:** Associated with **Subacute Sclerosing Panencephalitis (SSPE)**. While it involves cognitive decline, the pathology shows widespread gliosis and Warthin-Finkeldey giant cells, not the specific JC virus-induced oligodendrocyte changes. * **D. Syphilis:** Neurosyphilis (Tabes dorsalis or General Paresis) involves the dorsal columns or cortical atrophy with "rod cells" (microglia), but not primary demyelination of white matter with viral inclusions. ### **High-Yield Clinical Pearls for NEET-PG** * **JC Virus:** "JC" stands for John Cunningham (the first patient). * **MRI Finding:** Characterized by **non-enhancing**, multifocal T2/FLAIR hyperintensities in the subcortical white matter (sparing the cortex) [1]. * **Target Cell:** Oligodendrocytes (leading to demyelination) [1]. * **Differential:** Always differentiate from **HIV Encephalitis** (Microglial nodules/Multinucleated giant cells) and **Cerebral Toxoplasmosis** (Ring-enhancing lesions). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1280-1281.
Question 183: All of the following are true about Arnold-Chiari malformation except:
- A. Type I Chiari malformation is displacement of cerebellar tonsil into cervical canal.
- B. Type II Chiari malformation is associated with syringomyelia of cervical canal. (Correct Answer)
- C. Type II Chiari malformation is characterized by elongation of the 4th ventricle and kinking of the brainstem, with displacement of the inferior vermis, pons, and medulla into the cervical canal.
- D. Type I Chiari malformation is not associated with hydrocephalus.
Explanation: ### Explanation **1. Why Option B is the "Except" (Correct Answer):** While both Type I and Type II Chiari malformations can be associated with syringomyelia, **Type II** is classically and almost universally associated with **Myelomeningocele** (lumbar region). Syringomyelia is more frequently linked with **Type I Chiari malformation** (seen in approximately 30-40% of cases) [1]. In the context of NEET-PG questions, the hallmark association for Type II is the neural tube defect (myelomeningocele), making Option B the least accurate statement compared to the classic definitions of the other options. **2. Analysis of Other Options:** * **Option A:** This is a correct definition. **Type I** involves the downward displacement of the **cerebellar tonsils** (usually >5mm) through the foramen magnum [1]. It is often asymptomatic until adulthood. * **Option C:** This is a correct anatomical description of **Type II (Classic Chiari)**. It involves a small posterior fossa leading to the downward displacement of the **vermis, pons, and medulla**, resulting in the characteristic "Z-shaped" kinking of the medulla and elongation of the 4th ventricle [1]. * **Option D:** This is generally true. **Type I** is typically a disorder of CSF flow dynamics but rarely causes overt obstructive hydrocephalus. In contrast, **Type II** is almost always associated with hydrocephalus due to the obstruction of the exit foramina of the 4th ventricle [1]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Chiari Type I:** Most common; associated with **Syringomyelia** (cape-like loss of pain and temperature) and **Basilar invagination** [1]. * **Chiari Type II:** Associated with **Lumbar Myelomeningocele** and **Hydrocephalus**. Look for "Beaked midbrain" on MRI. * **Chiari Type III:** Rare; involves displacement of the cerebellum into a **cervical/occipital encephalocele**. * **Chiari Type IV:** Characterized by **cerebellar hypoplasia** rather than displacement. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 718-719.
Question 184: Which of the following conditions is characterized by the presence of Lewy bodies?
- A. Alzheimer's disease
- B. Rabies
- C. Parkinsonism (Correct Answer)
- D. Multi-infarct dementia
Explanation: **Explanation:** **Correct Option: C. Parkinsonism** Lewy bodies are the pathological hallmark of **Parkinson’s Disease (Idiopathic Parkinsonism)** and Lewy Body Dementia [1], [3]. Microscopically, they appear as **eosinophilic, round, intracytoplasmic inclusions** with a dense core and a surrounding pale halo [3]. They are primarily composed of **alpha-synuclein** protein, along with ubiquitin and neurofilaments [1]. In Parkinson’s disease, these inclusions are typically found in the pigmented neurons of the **substantia nigra pars compacta**, leading to neuronal degeneration and dopamine depletion [2]. **Incorrect Options:** * **A. Alzheimer’s disease:** Characterized by extracellular **Amyloid-beta plaques** and intracellular **Neurofibrillary tangles** (composed of hyperphosphorylated Tau protein) [4]. * **B. Rabies:** Characterized by **Negri bodies**, which are eosinophilic cytoplasmic inclusions found specifically in the pyramidal cells of the hippocampus and Purkinje cells of the cerebellum. * **D. Multi-infarct dementia:** Caused by cumulative damage from multiple small strokes (vascular etiology); it is characterized by "lacunar infarcts" and gliosis rather than specific proteinaceous inclusions. **High-Yield Clinical Pearls for NEET-PG:** * **Stain:** Lewy bodies are best visualized using **alpha-synuclein immunohistochemistry** [3]. * **Location:** In Parkinson's, they are in the brainstem (substantia nigra); in Lewy Body Dementia, they are widespread in the **cerebral cortex** [2], [3]. * **Dementia vs. Parkinsonism:** If motor symptoms precede dementia by >1 year, it is Parkinson’s. If dementia occurs first or concurrently with motor symptoms, it is Dementia with Lewy Bodies (DLB). * **Other Inclusions:** Remember **Hirano bodies** (actin-rich) and **Pick bodies** (Tau-positive) as other high-yield neuropathology findings. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1296-1297. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 723-724. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1297-1298. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 719-720.
Question 185: Which of the following brain tumors arises from arachnoid villi?
- A. Medulloblastoma
- B. Ependymoma
- C. Meningioma (Correct Answer)
- D. Glioma
Explanation: ### Explanation **Meningiomas** are the most common benign intracranial tumors. They arise from the **arachnoid cap cells**, which are found in the **arachnoid villi** (granulations). These cells are responsible for the reabsorption of cerebrospinal fluid (CSF) into the dural venous sinuses. Because they arise from the meninges rather than the brain parenchyma, they are typically extra-axial and well-circumscribed [2]. **Analysis of Incorrect Options:** * **Medulloblastoma:** A highly malignant primitive neuroectodermal tumor (PNET) that arises from the **external granular layer of the cerebellum** (neuroectoderm), typically in the roof of the fourth ventricle in children. * **Ependymoma:** Arises from the **ependymal cells** lining the ventricular system or the central canal of the spinal cord. In children, they commonly occur in the fourth ventricle. * **Glioma:** A broad category of tumors (including astrocytomas, oligodendrogliomas, and glioblastomas) that originate from the **glial cells** (supporting cells) of the brain parenchyma [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Look for **Psammoma bodies** (laminated calcifications) and **Whorled patterns** of spindle cells [1]. * **Genetics:** Frequently associated with **NF2 (Neurofibromatosis type 2)** on chromosome 22 [1], [2]. * **Radiology:** Characterized by a **"Dural Tail" sign** on contrast-enhanced MRI [2]. * **Risk Factors:** Prior radiation exposure and female gender (due to progesterone receptors on the tumor cells) [3]. * **Common Sites:** Parasagittal region, olfactory groove, and sphenoid wing. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1316-1317. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1307-1308.
Question 186: Which of the following brain tumors does not spread via CSF?
- A. Germ cell tumors
- B. Medulloblastoma
- C. CNS lymphoma
- D. Craniopharyngioma (Correct Answer)
Explanation: **Explanation:** The spread of tumor cells via the Cerebrospinal Fluid (CSF) is known as **leptomeningeal carcinomatosis** or "drop metastasis." This occurs when malignant cells shed into the subarachnoid space and circulate through the ventricular system [1], [3]. **Why Craniopharyngioma is the correct answer:** Craniopharyngiomas are **benign (WHO Grade 1)**, slow-growing tumors derived from remnants of Rathke’s pouch. They are typically cystic, well-circumscribed, and located in the suprasellar region. Because they are histologically benign and lack an invasive nature into the ventricular system or subarachnoid space, they do **not** spread via CSF. **Analysis of Incorrect Options:** * **Medulloblastoma:** This is a highly malignant primitive neuroectodermal tumor (PNET) of the cerebellum [1]. It is notorious for "drop metastasis" to the spinal cord; hence, craniospinal axis imaging is mandatory [3]. * **Germ Cell Tumors (e.g., Germinoma):** Commonly found in the pineal or suprasellar regions, these are highly friable and frequently disseminate through the ventricular system [4]. * **CNS Lymphoma:** Primary CNS lymphomas are aggressive (usually Diffuse Large B-cell type) and often involve the periventricular white matter, leading to frequent CSF seeding [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Common tumors spreading via CSF:** Medulloblastoma (most common) [1], Ependymoma [5], Pineoblastoma, Germinoma [4], and CNS Lymphoma [2]. * **Craniopharyngioma Hallmark:** Look for "machinery oil" fluid (cholesterol crystals) and calcification on CT (seen in 90% of pediatric cases). * **Adamantinomatous type:** Most common in children; characterized by "wet keratin" and *CTNNB1* (β-catenin) mutations. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1314-1315. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1315-1316. [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 Endocrine System, pp. 1140-1141. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1312-1313.
Question 187: Craniopharyngiomas are basically?
- A. Tumors resembling osteomas
- B. Tumors derived from Rathke's Pouch (Correct Answer)
- C. Tumors similar to glottis cancer
- D. Adenocarcinomas
Explanation: ### Explanation **Craniopharyngiomas** are benign but locally aggressive tumors of the sellar and suprasellar region [1]. They are embryologically derived from the remnants of **Rathke’s pouch**, which is an ectodermal outpocketing of the primitive oral cavity (stomodeum) that normally gives rise to the anterior pituitary (adenohypophysis). #### Why Option B is Correct: During development, if cells from Rathke’s pouch fail to migrate or involute properly, they can undergo neoplastic transformation. This origin explains why these tumors often contain squamous epithelium and keratin, reflecting their oral ectoderm ancestry. #### Why Other Options are Incorrect: * **Option A:** While craniopharyngiomas (specifically the Adamantinomatous type) frequently show **dystrophic calcification** that may appear bone-like on imaging, they are epithelial tumors, not mesenchymal bone-forming tumors like osteomas. * **Option C:** There is no histological or clinical similarity between craniopharyngiomas and glottis (laryngeal) cancer. * **Option D:** Although they arise from glandular precursors, they are categorized as benign epithelial tumors (WHO Grade I), not invasive adenocarcinomas. #### NEET-PG High-Yield Pearls: 1. **Bimodal Distribution:** Peaks in children (5–14 years) and adults (50–75 years). 2. **Two Histological Types:** * **Adamantinomatous:** Most common (especially in children); characterized by "wet keratin," calcifications, and a "machinery oil" fluid within cysts. Associated with *CTNNB1* (β-catenin) mutations. * **Papillary:** Seen almost exclusively in adults; lacks calcification and "machinery oil." Associated with *BRAF V600E* mutations. 3. **Clinical Presentation:** Often presents with **bitemporal hemianopia** (due to optic chiasm compression) and endocrine dysfunction (growth retardation or diabetes insipidus) [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 416-417.
Question 188: In tuberculous meningitis, where do the exudates tend to be most severe?
- A. Over the frontal regions of the brain
- B. At the base of the brain (Correct Answer)
- C. Around the cerebellum
- D. In the ventricles
Explanation: ### Explanation **Correct Answer: B. At the base of the brain** **Underlying Medical Concept:** Tuberculous meningitis (TBM) is characterized by a chronic inflammatory process. The hallmark of TBM is the formation of a thick, gelatinous, and creamy **basal exudate**. This occurs because the *Mycobacterium tuberculosis* bacilli typically reach the subarachnoid space via the rupture of a subpial or subependymal focus (Rich focus) [1]. The gravity-dependent flow of CSF and the complex anatomy of the basal cisterns (interpeduncular fossa, optic chiasm, and pons) trap the inflammatory debris, leading to dense accumulation at the **base of the brain** [1]. **Analysis of Incorrect Options:** * **A. Over the frontal regions:** This is more characteristic of **acute pyogenic (bacterial) meningitis**, where exudates are often distributed over the cerebral convexities. * **C. Around the cerebellum:** While exudates can spread to the cerebellum, it is not the primary or most severe site of accumulation compared to the basal cisterns. * **D. In the ventricles:** While TBM can cause ependymitis or choroid plexitis, the primary site of severe exudate formation is the subarachnoid space at the base, not the ventricular system itself (though it often leads to obstructive hydrocephalus) [2]. **NEET-PG High-Yield Pearls:** * **Rich Focus:** The initial subpial/subependymal tubercle that ruptures into the subarachnoid space. * **Complications:** The basal exudate often encases cranial nerves (causing palsies, most commonly **CN VI**) and involves the Circle of Willis, leading to **血管炎 and hemorrhagic infarcts**. * **CSF Findings:** Classic "cobweb" or "pellicle" formation on standing, high protein, low glucose, and lymphocytic pleocytosis. * **Hydrocephalus:** TBM is the most common cause of communicating hydrocephalus in many endemic regions due to the blockage of CSF flow by basal exudates [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 709-710. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 703-704.
Question 189: A 40-year-old woman presents with severe headaches and dizziness. An MRI reveals a brain tumor, and a biopsy confirms it as a melanoma. She dies 2 months later. Pigmented lesions are not seen on her skin or scalp at the time of diagnosis or during postmortem examination. Which of the following is the most likely source of the malignant melanoma cells?
- A. Superior sagittal sinus
- B. Sphenoidal sinus
- C. Retina of the eye (Correct Answer)
- D. Pituitary gland
Explanation: **Explanation:** The correct answer is **C. Retina of the eye.** **1. Why the Retina is the most likely source:** Malignant melanoma primarily arises from melanocytes. While most melanomas originate in the skin, they can also arise from non-cutaneous sites containing melanocytes, such as the **uveal tract of the eye** (iris, ciliary body, and choroid) [1], mucosal surfaces, and the leptomeninges. In this clinical scenario, the absence of cutaneous or scalp lesions suggests an occult primary site. The eye is the most common non-cutaneous site for melanoma [1], [2]. These tumors can metastasize hematogenously to the brain [3], or primary leptomeningeal melanomas can occur within the CNS itself. **2. Why other options are incorrect:** * **A. Superior sagittal sinus:** This is a dural venous sinus. While primary CNS melanomas can involve the meninges, the sinus itself does not contain the melanocytic populations required to be a "source" of melanoma. * **B. Sphenoidal sinus:** While mucosal melanomas can occur in the nasal cavity or paranasal sinuses, they are significantly rarer than uveal (retinal/choroidal) melanomas. * **D. Pituitary gland:** The pituitary gland is composed of adenohypophyseal cells (ectoderm) and neurohypophyseal tissue (neuroectoderm), but it is not a recognized primary site for melanocytic transformation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common primary intraocular tumor in adults:** Uveal Melanoma [1]. * **Metastatic Pattern:** Uveal melanomas have a high predilection for spreading to the **liver** (most common) and the **brain** [3]. * **Cell of Origin:** Melanocytes are derived from the **neural crest**. * **Primary CNS Melanoma:** Rare; usually arises from melanocytes within the leptomeninges (pia and arachnoid mater), most commonly in the base of the brain or the spinal cord. * **Rule of Thumb:** If a patient has "Amelanotic" or "Occult" melanoma symptoms with no skin findings, always check the **eyes** and **anogenital mucosa**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Eye, pp. 1334-1335. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 737-738. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1317-1318.
Question 190: Misfolded amyloid deposition in the brain is seen in which of the following conditions?
- A. Creutzfeldt-jakob disease
- B. Alzheimer's disease (Correct Answer)
- C. HIV-encephalopathy
- D. Gaucher's disease
Explanation: **Explanation:** **Alzheimer’s Disease (Correct Answer):** The hallmark of Alzheimer’s disease is the extracellular deposition of **Amyloid-beta (Aβ) plaques** [1], [4]. These are formed by the abnormal cleavage of Amyloid Precursor Protein (APP) by β-secretase and γ-secretase, leading to misfolded Aβ peptides that aggregate into insoluble fibrils. Additionally, intracellular **Tau protein** hyperphosphorylation leads to Neurofibrillary Tangles (NFTs) [1], [2]. **Analysis of Incorrect Options:** * **Creutzfeldt-Jakob Disease (CJD):** While CJD involves protein misfolding, the culprit is the **Prion protein (PrPsc)**. Although PrPsc can form "amyloid-like" plaques in some variants (like Kuru or vCJD), the classic pathological finding is **spongiform encephalopathy** (vacuolation of neurons/gray matter) rather than systemic or Aβ amyloid. * **HIV-Encephalopathy:** This is characterized by the formation of **Microglial nodules** and **Multinucleated giant cells**. It is a viral-mediated inflammatory process, not a primary amyloidosis. * **Gaucher’s Disease:** This is a **Lysosomal Storage Disorder** caused by a deficiency of the enzyme Glucocerebrosidase, leading to the accumulation of glucocerebroside in macrophages (Gaucher cells). It does not involve amyloid deposition. **NEET-PG High-Yield Pearls:** * **Staining:** Amyloid in the brain stains with **Congo Red** (showing apple-green birefringence) and **Thioflavin T** [3]. * **Aβ Origin:** Derived from APP (Chromosome 21); this explains why Down Syndrome patients develop Alzheimer's early [4]. * **ApoE4:** The presence of the Apolipoprotein E4 allele increases the risk of Aβ deposition. * **Hirano Bodies:** Another high-yield finding in Alzheimer’s—eosinophilic, rod-like inclusions in hippocampus neurons containing actin. **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. 721-722. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 264-266. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 719-721.
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Cellular Pathology of the Nervous System
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Demyelinating Diseases
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Neurodegenerative Diseases
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CNS Tumors
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Peripheral Nerve Disorders
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