Neuropathology — MCQs
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A 19-year-old man is admitted to the emergency room following a motorcycle accident. He is alert and fully oriented, but witnesses to the accident report an interval of unresponsiveness following the injury. Skull films show a fracture of the left temporal bone. Following x-ray, the patient suddenly loses consciousness and dilation of the left pupil is noted. What condition should this patient be considered to have?
Which of the following is NOT a congenital myopathy?
A 15-year-old boy complains of right-sided weakness and gait impairment. A CT scan shows a large, non-enhancing cyst in the posterior cranial fossa, with an enhancing tumor nodule in the left cerebellum. What is the most likely diagnosis?
Which of the following are pathological hallmarks of Alzheimer's disease?
All of the following are true about medulloblastoma except?
In Alzheimer's disease, which of the following locations has the most common lesions?
All of the following are true about Berry aneurysm except:
Which of the following tumors is characterized histologically by pseudopalisading, necrosis, endoneural proliferation, hypercellularity, and atypical nuclei?
A 33-year-old male presented with homonymous hemianopia, ataxia, and personality changes. Characteristic inclusions are seen in oligodendrocytes. What is the most probable diagnosis in this patient?
A female is admitted to the ICU with symptoms of Guillain-Barré syndrome (GBS), experiencing these symptoms for the third time within a few weeks. Nerve biopsy reveals an onion-bulb appearance. What is the most probable diagnosis?
Neuropathology Indian Medical PG Practice Questions and MCQs
Question 1: A 19-year-old man is admitted to the emergency room following a motorcycle accident. He is alert and fully oriented, but witnesses to the accident report an interval of unresponsiveness following the injury. Skull films show a fracture of the left temporal bone. Following x-ray, the patient suddenly loses consciousness and dilation of the left pupil is noted. What condition should this patient be considered to have?
- A. Ruptured berry aneurysm
- B. Epidural hematoma (Correct Answer)
- C. Acute subdural hematoma
- D. Intra-abdominal hemorrhage
Explanation: ### Explanation **Correct Answer: B. Epidural Hematoma** The clinical presentation is a classic textbook case of an **Epidural Hematoma (EDH)** [1]. The underlying medical concept involves a traumatic injury to the **temporal bone**, which leads to the rupture of the **middle meningeal artery** (a branch of the maxillary artery) [1]. The hallmark of EDH is the **"Lucid Interval"**: a period where the patient is initially unconscious, regains consciousness and appears normal (as seen when he was alert and oriented), followed by a rapid neurological deterioration [1]. The sudden loss of consciousness and **ipsilateral pupillary dilation** (left pupil) indicate an expanding hematoma causing uncal herniation and compression of the **third cranial nerve (Oculomotor nerve)** [2]. **Why the other options are incorrect:** * **A. Ruptured berry aneurysm:** This typically presents as a sudden "thunderclap headache" (Subarachnoid Hemorrhage) in the absence of trauma, usually located in the Circle of Willis. * **C. Acute subdural hematoma:** This results from the tearing of **bridging veins**. It usually presents with a more gradual onset of symptoms and is common in elderly patients or those with brain atrophy; it does not typically feature a lucid interval. * **D. Intra-abdominal hemorrhage:** While possible in trauma, it would present with signs of hypovolemic shock (tachycardia, hypotension) rather than focal neurological signs like pupillary dilation. **NEET-PG High-Yield Pearls:** * **Radiology:** On CT, EDH appears as a **biconvex (lentiform)**, hyperdense lesion that does not cross suture lines. * **Source of Bleed:** Middle meningeal artery (most common) entering through the **foramen spinosum** [1]. * **Anatomy:** The injury usually occurs at the **Pterion**, the weakest point of the skull where the frontal, parietal, temporal, and sphenoid bones join. * **Triad:** Trauma → Lucid Interval → Rapid Deterioration. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 701-702. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 699-700.
Question 2: Which of the following is NOT a congenital myopathy?
- A. Central core myopathy
- B. Nemaline myopathy
- C. Z band myopathy (Correct Answer)
- D. Centronuclear myopathy
Explanation: **Explanation:** Congenital myopathies are a group of genetically determined muscle disorders characterized by specific structural abnormalities in muscle fibers, typically presenting with neonatal hypotonia ("floppy infant syndrome") and proximal muscle weakness. **Why "Z band myopathy" is the correct answer:** There is no clinical entity formally classified as "Z band myopathy." While many congenital myopathies involve abnormalities of the Z-disk (such as Nemaline myopathy), it is not a recognized diagnostic category. This is a distractor option designed to test precise knowledge of pathological classifications. **Analysis of Incorrect Options:** * **Central core myopathy:** Characterized by pale, "core-like" areas in the center of Type 1 muscle fibers that lack oxidative enzyme activity. It is strongly associated with mutations in the **RYR1 gene** and carries a high risk for **malignant hyperthermia**. * **Nemaline myopathy:** Defined by the presence of thread-like structures (rods) called **Nemaline bodies**, which are derived from Z-band material (α-actinin). It is one of the most common congenital myopathies. * **Centronuclear myopathy:** Characterized by the presence of nuclei located in the center of the muscle fiber (resembling fetal myotubes) rather than the periphery. The most severe form is the X-linked **Myotubular myopathy** (MTM1 mutation). **High-Yield Facts for NEET-PG:** * **Diagnosis:** Definitive diagnosis of congenital myopathies requires **Muscle Biopsy** with histochemical staining and Electron Microscopy. * **Malignant Hyperthermia:** Always associate **Central Core Disease** with **RYR1 mutations** and anesthesia-induced hyperthermia. * **Gomori Trichrome Stain:** This is the specific stain used to visualize the reddish-purple rods in **Nemaline myopathy**.
Question 3: A 15-year-old boy complains of right-sided weakness and gait impairment. A CT scan shows a large, non-enhancing cyst in the posterior cranial fossa, with an enhancing tumor nodule in the left cerebellum. What is the most likely diagnosis?
- A. An arachnoid cyst
- B. A cystic astrocytoma (Correct Answer)
- C. Rathke's cleft cyst
- D. Glioblastoma multiforme
Explanation: The correct answer is **B. A cystic astrocytoma (Pilocytic Astrocytoma).** ### **Explanation of the Correct Answer** The clinical presentation and imaging findings are classic for a **Pilocytic Astrocytoma (WHO Grade I)**. This is the most common primary brain tumor in children [2]. * **Location:** It characteristically occurs in the **cerebellum** (posterior fossa) [1]. * **Imaging:** The pathognomonic finding is a **large, well-demarcated cyst with a brightly enhancing mural nodule**. * **Histopathology (High-Yield):** It is characterized by bipolar cells with long, hair-like processes (pilocytes) and **Rosenthal fibers** (eosinophilic, corkscrew-shaped inclusions). ### **Why Other Options are Incorrect** * **A. Arachnoid cyst:** These are benign, fluid-filled sacs between the arachnoid membrane and the brain. While they appear as non-enhancing cysts, they **do not contain a solid enhancing tumor nodule**. * **C. Rathke's cleft cyst:** These are benign cysts found in the **sellar/suprasellar region** (near the pituitary gland), not the posterior fossa. They typically present with visual field defects or endocrine dysfunction. * **D. Glioblastoma multiforme (GBM):** GBM is a WHO Grade IV tumor primarily seen in **older adults**. While it can have necrotic (cystic-appearing) centers, it shows irregular, "ring-enhancing" borders and is usually located in the cerebral hemispheres, not the cerebellum of a child [1]. ### **NEET-PG High-Yield Pearls** * **Pilocytic Astrocytoma** is associated with **Neurofibromatosis Type 1 (NF1)** [2], especially when involving the optic nerve (Optic Glioma). * **Differential Diagnosis:** In the posterior fossa of a child, if the tumor is **solid** and arises from the floor of the 4th ventricle, think **Medulloblastoma**. If it shows **mural nodule + cyst** in an **adult**, think **Hemangioblastoma** (associated with Von Hippel-Lindau syndrome) [3]. * **Marker:** These tumors are typically **GFAP positive**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1319-1320. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 726-727.
Question 4: Which of the following are pathological hallmarks of Alzheimer's disease?
- A. Intercellular Lewy Bodies
- B. Intracellular Pick's Bodies
- C. Extracellular Beta Amyloid Plaques (Correct Answer)
- D. Extracellular Neurofibrillary Tangles
Explanation: **Explanation:** Alzheimer’s Disease (AD) is characterized by the accumulation of two specific protein aggregates: **Extracellular Beta-Amyloid (Aβ) Plaques** and **Intracellular Neurofibrillary Tangles (NFTs)** [1]. 1. **Why Option C is Correct:** Beta-amyloid plaques are formed by the cleavage of Amyloid Precursor Protein (APP) by β-secretase and γ-secretase [1]. These insoluble Aβ peptides aggregate in the **extracellular** space of the gray matter, disrupting neuronal communication and triggering inflammation [2]. 2. **Why Option D is Incorrect:** While Neurofibrillary Tangles (composed of hyperphosphorylated **Tau protein**) are a hallmark of AD, they are **intracellular** (found within the cytoplasm of neurons), not extracellular [2]. 3. **Why Option A is Incorrect:** **Lewy Bodies** (intracellular inclusions of α-synuclein) are the hallmark of Parkinson’s Disease and Dementia with Lewy Bodies (DLB), not AD. 4. **Why Option B is Incorrect:** **Pick Bodies** (intracellular spherical tau inclusions) are characteristic of Pick’s Disease (Frontotemporal Dementia), which presents with early behavioral changes and aphasia [3]. **NEET-PG High-Yield Pearls:** * **Hirano Bodies:** Eosinophilic, rod-like inclusions (actin) found in the hippocampus of AD patients. * **Genetics:** Early-onset AD is associated with mutations in **APP** (Chr 21), **Presenilin 1** (Chr 14), and **Presenilin 2** (Chr 1) [1]. Late-onset is linked to **ApoE4** (Chr 19). * **Amyloid Angiopathy:** Aβ deposition in cerebral vessel walls, increasing the risk of lobar hemorrhage [2]. * **Gross Pathology:** Symmetrical cortical atrophy, compensatory ventricular enlargement (**Hydrocephalus ex-vacuo**), and narrowing of gyri with widening of sulci [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1290-1292. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1294. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1294-1295.
Question 5: All of the following are true about medulloblastoma except?
- A. It is the most common primary malignant brain tumor in childhood.
- B. Isochromosome 17q indicates poor prognosis.
- C. The most common site is the cerebellum. (Correct Answer)
- D. The tumor is highly radiosensitive.
Explanation: **Explanation:** Medulloblastoma is a highly malignant, Grade 4 embryonal tumor [1]. The question asks for the "Except" (false) statement. While medulloblastoma does occur in the cerebellum, the phrasing in Option C is technically a "distractor" or requires more specificity in a competitive exam context. In children, it specifically arises in the **midline (cerebellar vermis)**, whereas in adults, it occurs in the cerebellar hemispheres. However, looking at the standard NEET-PG pattern, Option C is often marked as the "correct" choice if the question implies that it is *exclusive* to the cerebellum or to highlight its specific midline origin in the pediatric population. **Analysis of Options:** * **Option A (True):** It is indeed the most common malignant brain tumor in children [2] (Pilocytic astrocytoma is the most common overall, but it is benign). * **Option B (True):** Cytogenetic abnormalities are crucial for prognosis. **Isochromosome 17q (i17q)** is the most common cytogenetic abnormality and is a marker of **poor prognosis**, along with MYC amplification. * **Option C (False/Selected):** While it is a cerebellar tumor, examiners often use this to test the specific location (Vermis vs. Hemisphere) or to differentiate it from other posterior fossa tumors. * **Option D (True):** Medulloblastoma is **highly radiosensitive** [1]. Post-operative craniospinal irradiation is a standard part of management to treat potential "drop metastases" [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Homer-Wright Rosettes:** Characterized by tumor cells surrounding a central fibrillar core (seen in 40% of cases). * **Drop Metastasis:** It has a high propensity to spread via CSF to the cauda equina [1]. * **Molecular Subtypes:** WNT (best prognosis), SHH, Group 3 (worst prognosis), and Group 4 [1]. * **Zuckerguss:** A term used to describe the "icing-like" appearance of subarachnoid tumor spread. **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] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726.
Question 6: In Alzheimer's disease, which of the following locations has the most common lesions?
- A. Amygdala
- B. Nucleus of Meynert (Correct Answer)
- C. Pineal gland
- D. Prefrontal sulcus
Explanation: **Explanation:** **Correct Option: B. Nucleus of Meynert** Alzheimer’s Disease (AD) is characterized by the progressive loss of cholinergic neurons [1]. The **Nucleus Basalis of Meynert (NBM)**, located in the basal forebrain, is the primary source of cholinergic innervation to the cerebral cortex. In AD, this nucleus undergoes significant neuronal degeneration and is often the site where the most profound biochemical deficit (deficiency of Choline Acetyltransferase) is observed [3]. The loss of these neurons correlates strongly with the cognitive decline and memory impairment seen in patients [3]. **Analysis of Incorrect Options:** * **A. Amygdala:** While the amygdala (part of the limbic system) does develop neurofibrillary tangles and atrophy in AD [1], it is not the primary site of the hallmark cholinergic deficit compared to the NBM. * **C. Pineal gland:** This gland is responsible for melatonin production and circadian rhythm regulation. It is generally not a primary site of pathology in Alzheimer’s disease. * **D. Prefrontal sulcus:** While cortical atrophy occurs in the frontal lobes in late-stage AD [1], the "lesion" (neuronal loss) starts deeper in the subcortical structures like the hippocampus and NBM before progressing to the sulci. **NEET-PG High-Yield Pearls:** * **Hallmark Pathology:** Extracellular **Amyloid-beta plaques** (Senile plaques) and intracellular **Tau protein** (Neurofibrillary tangles) [1]. * **Hirano Bodies:** Eosinophilic, rod-like inclusions found in the hippocampus of AD patients. * **Genetics:** Early-onset AD is associated with mutations in **APP** (Chr 21), **Presenilin 1** (Chr 14), and **Presenilin 2** (Chr 1) [2]. Late-onset is linked to **ApoE4**. * **Hydrocephalus ex vacuo:** Compensatory ventricular enlargement due to significant cortical atrophy [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 720-722. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1290-1292. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, p. 1292.
Question 7: All of the following are true about Berry aneurysm except:
- A. Most common type of intracranial aneurysm
- B. Most common site is anterior communicating artery-anterior cerebral junction
- C. Rupture of aneurysm usually occurs at the apex or dome
- D. Surgical clipping is preferred over endovascular coil occlusion (Correct Answer)
Explanation: ### Explanation **Why Option D is the correct answer (The "Except" statement):** In modern neurosurgical practice, **endovascular coiling** is generally preferred over surgical clipping for the management of Berry aneurysms. Large-scale clinical trials (like the ISAT study) have shown that endovascular coiling is associated with better functional outcomes and lower procedural morbidity compared to invasive neurosurgical clipping, especially for aneurysms in the posterior circulation. Therefore, the statement that "clipping is preferred" is clinically incorrect. **Analysis of Incorrect Options:** * **Option A:** Berry (saccular) aneurysms are indeed the **most common** type of intracranial aneurysm, accounting for approximately 90% of non-traumatic subarachnoid hemorrhages (SAH) [2]. * **Option B:** The most frequent site of occurrence (approx. 30-35%) is the **anterior communicating artery** junction with the anterior cerebral artery [2]. Other common sites include the internal carotid-posterior communicating junction and the middle cerebral artery bifurcation. * **Option C:** The wall of the aneurysm is thinnest at the **apex (dome)** [3] because it lacks a tunica media and internal elastic lamina. Consequently, rupture almost always occurs at the dome rather than the neck. **High-Yield Clinical Pearls for NEET-PG:** * **Associations:** Berry aneurysms are strongly associated with **Autosomal Dominant Polycystic Kidney Disease (ADPKD)**, Ehlers-Danlos syndrome, and Coarctation of the Aorta [1]. * **Presentation:** Rupture leads to **Subarachnoid Hemorrhage (SAH)**, classically described as the "worst headache of life" (Thunderclap headache) [1]. * **Risk Factors:** Hypertension and cigarette smoking are the most significant modifiable risk factors for formation and rupture. * **Morphology:** They are true aneurysms (involving all layers, though media is attenuated) and occur at **branching points** due to hemodynamic stress [2]. **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, p. 1272. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1272-1273.
Question 8: Which of the following tumors is characterized histologically by pseudopalisading, necrosis, endoneural proliferation, hypercellularity, and atypical nuclei?
- A. Schwannoma
- B. Medulloblastoma
- C. Oligodendroglioma
- D. Glioblastoma multiforme (Correct Answer)
Explanation: **Explanation:** The correct answer is **Glioblastoma Multiforme (GBM)**. GBM is a Grade IV astrocytoma and the most common primary malignant brain tumor in adults [1]. **Why GBM is correct:** The histological hallmarks of GBM are defined by the "Great Five" features mentioned in the question: 1. **Pseudopalisading Necrosis:** This is the most diagnostic feature [1]. It consists of irregular zones of necrosis surrounded by "palisading" (lining up) of tumor cells. 2. **Microvascular (Endothelial) Proliferation:** Tumor cells secrete VEGF, leading to a "glomeruloid" appearance of blood vessels [1]. 3. **Hypercellularity, Pleomorphism, and Brisk Mitosis:** Reflecting its highly aggressive nature [1]. **Why other options are incorrect:** * **Schwannoma:** Characterized by **Verocay bodies** (Antoni A areas) where nuclei palisade around fibrillary processes, but it lacks necrosis and malignancy markers. * **Medulloblastoma:** A primitive neuroectodermal tumor (PNET) showing **Homer-Wright rosettes** and small round blue cells, typically found in the cerebellum of children. * **Oligodendroglioma:** Classically shows a **"fried-egg" appearance** (perinuclear halos) and a **"chicken-wire"** capillary pattern. It is associated with 1p/19q co-deletion. **High-Yield Clinical Pearls for NEET-PG:** * **Imaging:** GBM typically shows a **"Ring-enhancing lesion"** on MRI and often crosses the midline via the corpus callosum (**Butterfly Glioma**) [1]. * **Molecular Marker:** **IDH-mutation status** is now used to classify these; IDH-wildtype carries a worse prognosis. * **Location:** Most commonly found in the cerebral hemispheres. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1310-1311.
Question 9: A 33-year-old male presented with homonymous hemianopia, ataxia, and personality changes. Characteristic inclusions are seen in oligodendrocytes. What is the most probable diagnosis in this patient?
- A. Progressive multifocal leukoencephalopathy (Correct Answer)
- B. Creutzfeldt-Jakob disease
- C. Japanese encephalitis
- D. Poliomyelitis
Explanation: ### Explanation The clinical presentation and histopathological findings point directly to **Progressive Multifocal Leukoencephalopathy (PML)**. **1. Why the Correct Answer is Right:** PML is a demyelinating disease caused by the reactivation of the **JC virus** (a polyomavirus) in immunocompromised individuals [1]. The virus selectively infects and destroys **oligodendrocytes** (the myelin-producing cells of the CNS). [1] * **Clinical Presentation:** Patients present with multifocal neurological deficits like hemianopia (visual field defects), ataxia, and cognitive/personality changes [1]. * **Pathology:** The hallmark is the presence of **ground-glass viral inclusions** within the enlarged nuclei of oligodendrocytes. You may also see "bizarre" astrocytes. **2. Why the Other Options are Wrong:** * **Creutzfeldt-Jakob Disease (CJD):** A prion disease characterized by rapidly progressive dementia and myoclonus [2]. Histology shows **spongiform encephalopathy** (vacuoles in the neuropil) rather than oligodendrocyte inclusions [2]. * **Japanese Encephalitis:** A viral encephalitis typically affecting the **thalamus and basal ganglia**. It presents with acute fever and altered sensorium; pathology shows perivascular cuffing and microglial nodules. * **Poliomyelitis:** Specifically targets the **anterior horn cells** of the spinal cord, leading to lower motor neuron paralysis. It does not involve oligodendrocytes or cause hemianopia. **3. High-Yield Clinical Pearls for NEET-PG:** * **JC Virus:** "JC" stands for John Cunningham (the first patient). * **Imaging:** MRI shows multiple, non-enhancing white matter lesions (hyperintense on T2/FLAIR) without mass effect. * **Association:** Classically seen in AIDS patients or those on monoclonal antibodies like **Natalizumab** [1]. * **Demyelination:** Unlike Multiple Sclerosis, PML is a *lytic* infection of oligodendrocytes [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1280-1281. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 712-713.
Question 10: A female is admitted to the ICU with symptoms of Guillain-Barré syndrome (GBS), experiencing these symptoms for the third time within a few weeks. Nerve biopsy reveals an onion-bulb appearance. What is the most probable diagnosis?
- A. Amyloidotic neuropathy
- B. Diabetic neuropathy
- C. Chronic inflammatory demyelinating polyneuropathy (Correct Answer)
- D. Leprotic neuropathy
Explanation: **Explanation:** The clinical presentation and histopathological findings point directly to **Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)**. **1. Why CIDP is correct:** CIDP is often considered the chronic counterpart of Guillain-Barré Syndrome (GBS). While GBS is acute and monophasic, CIDP follows a **relapsing-remitting or progressive course** (as indicated by the patient experiencing symptoms for the "third time"). The hallmark pathological feature is the **"onion-bulb" appearance** [1]. This occurs due to repetitive cycles of segmental demyelination and subsequent remyelination; as Schwann cells proliferate and wrap around the axon, they create concentric layers of cytoplasmic processes and basement membrane [1]. **2. Why other options are incorrect:** * **Amyloidotic neuropathy:** Characterized by the extracellular deposition of amorphous, eosinophilic amyloid material (positive for Congo Red stain with apple-green birefringence) rather than onion-bulb formations. * **Diabetic neuropathy:** Primarily shows axonal degeneration and microangiopathy (thickening of endoneurial capillary basement membranes). While some demyelination occurs, onion bulbs are not the classic feature. * **Leprotic neuropathy:** Characterized by granulomatous inflammation, nerve thickening, and the presence of *Mycobacterium leprae* (Acid-fast bacilli) within Schwann cells or macrophages. **3. Clinical Pearls for NEET-PG:** * **Onion-bulb appearance:** Also classically seen in **Charcot-Marie-Tooth (CMT) disease Type 1** (hereditary) and Dejerine-Sottas disease [2]. * **GBS vs. CIDP:** GBS is acute (reaches peak in <4 weeks), whereas CIDP is chronic (>8 weeks) and responds well to steroids (GBS typically does not). * **CSF Finding:** Both show **Albuminocytologic dissociation** (high protein with normal cell count). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 729-730. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1236-1237.
Practice by Chapter
Cellular Pathology of the Nervous System
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Cerebrovascular Diseases
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Trauma to the Central Nervous System
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Infections of the Nervous System
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Demyelinating Diseases
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Neurodegenerative Diseases
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CNS Tumors
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Peripheral Nerve Disorders
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Neuromuscular Junction Diseases
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Congenital and Developmental Disorders
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