Neuropathology Practice Questions

Q: Which of the following is involved in the pathogenesis of myasthenia gravis?

Autoantibodies against acetylcholine receptors. The hallmark of MG pathogenesis is the production of autoantibodies against the nicotinic acetylcholine receptors (AChR) at the post-synaptic membrane [1]. These antibodies lead to a reduction in the number of functional receptors through three mechanisms: * Complement-mediated damage to the post-synaptic folds [2]. * Increased endocytosis and degradation of receptors (antigenic modulation). * Direct blockade of the ACh binding site. This results in a decreased end-plate potential, failing to trigger muscle fiber action potentials. **2. Why the Other Options are Incorrect:** * **Option A:** Mutations in **ryanodine receptors (RyR1)** are associated with **Malignant Hyperthermia** and Central Core Disease, not MG. * **Option C:** **Synaptobrevin** is a SNARE protein involved in vesicle docking. It is the target of **Tetanus toxin** and **Botulinum toxins (B, D, F, G)**, which prevent neurotransmitter release. * **Option D:** Autoantibodies against **P/Q-type voltage-gated calcium channels (VGCC)** are the cause of **Lambert-Eaton Myasthenic Syndrome (LEMS)** [4]. Unlike MG, LEMS is a presynaptic disorder [4]. **High-Yield Clinical Pearls for NEET-PG:** * **Associated Antibodies:** 85% of patients have anti-AChR antibodies. Of the remaining "seronegative" patients, many have antibodies against **MuSK** (Muscle-Specific Kinase) or **LRP4**. * **Thymus Involvement:** 75% of MG patients have thymus abnormalities (65% hyperplasia, 10% thymoma) [2]. * **Clinical Presentation:** Ptosis and diplopia are the most common initial symptoms (Ocular MG). Weakness typically worsens with activity and improves with rest [3].

Q: Which of the following statements is false with respect to demyelinating disorders?

Involves biochemical abnormality of myelin. To understand this question, one must distinguish between **Demyelinating** and **Dysmyelinating** disorders. ### **Explanation of the Correct Answer** **Option C is false** because demyelinating disorders (like Multiple Sclerosis) involve the **destruction of normally formed myelin** due to inflammation or toxins. The myelin itself is biochemically healthy until it is attacked. In contrast, **Dysmyelinating disorders** (Leukodystrophies) involve a **biochemical abnormality** where myelin is either not formed correctly or is chemically unstable due to genetic enzyme deficiencies. ### **Analysis of Other Options** * **Option A (True):** Increased blood-brain barrier (BBB) permeability is a hallmark of demyelinating diseases [1]. In MS, T-cells cross a "leaky" BBB to attack myelin basic protein, leading to inflammatory plaques. * **Option B (True):** Most autoimmune demyelinating disorders, especially Multiple Sclerosis, show a strong female predilection (typically a 3:1 ratio) [1]. * **Option C (True):** Multiple Sclerosis is indeed the most common primary demyelinating disease of the Central Nervous System (CNS) worldwide. ### **NEET-PG High-Yield Pearls** * **McDonald Criteria:** Used for the diagnosis of MS, focusing on "dissemination in time and space" [1]. * **CSF Findings:** Look for **Oligoclonal bands** (IgG) and an increased IgG index [1]. * **MRI Gold Standard:** Periventricular white matter lesions, specifically **Dawson’s Fingers** (oriented perpendicular to the lateral ventricles) [1]. * **Lhermitte’s Sign:** An electric shock-like sensation down the spine upon neck flexion, common in MS. * **Drug of Choice:** IV Methylprednisolone for acute attacks; Disease-Modifying Therapies (DMTs) like Ocrelizumab or Natalizumab for long-term management.

Q: Which of the following conditions classically shows a rosette-shaped arrangement of cells?

Ependymoma. **Explanation:** The correct answer is **Ependymoma**. In pathology, a "rosette" refers to a circular or flower-like arrangement of cells. Ependymomas are neuroepithelial tumors that classically exhibit two types of rosette formations [1]: 1. **Perivascular Pseudorosettes:** Tumor cells are arranged around a central blood vessel, separated by a fibrillary zone (cytoplasmic processes) [1]. This is a hallmark feature found in almost all ependymomas. 2. **True Ependymal Rosettes (True Rosettes):** Tumor cells surround a central lumen (resembling a small duct), mimicking the structure of 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 typically show a diffuse or fascicular growth pattern, not rosettes. * **C. Neurofibroma:** These are peripheral nerve sheath tumors characterized by a "shredded carrot" appearance due to wavy collagen bundles and spindle cells in a myxoid background. * **D. Lymphoma:** Malignant lymphomas generally present as a diffuse sheet of discohesive, monomorphic round cells. They do not form organized architectural patterns like rosettes. **High-Yield Clinical Pearls for NEET-PG:** * **Homer Wright Rosettes:** Cells surround a central fibrillary core (no lumen/vessel). Seen in **Neuroblastoma**, Medulloblastoma, and Retinoblastoma. * **Flexner-Wintersteiner Rosettes:** Cells surround a central lumen. Highly specific for **Retinoblastoma**. * **Call-Exner Bodies:** Small follicles filled with eosinophilic material, seen in **Granulosa Cell Tumors** (often confused with rosettes). * **Ependymoma Location:** Most common in the fourth ventricle in children and the spinal cord in adults [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1312-1313.

Q: Cowden syndrome is associated with which of the following findings?

Dysplastic gangliocytoma. **Explanation:** **Cowden Syndrome** (Multiple Hamartoma Syndrome) is an autosomal dominant disorder caused by a mutation in the **PTEN gene** on chromosome 10q23. PTEN is a tumor suppressor gene that inhibits the PI3K/AKT/mTOR pathway. **Why the correct answer is right:** The pathognomonic CNS manifestation of Cowden syndrome is **Lhermitte-Duclos Disease (LDD)**, also known as **Dysplastic Gangliocytoma of the cerebellum**. It is a rare, slowly progressing tumor characterized by the replacement of the internal granular layer of the cerebellum with large, dysplastic ganglion cells. On MRI, it classically presents as a "tiger-striped" cerebellar mass. **Why the incorrect options are wrong:** * **Medulloblastoma:** While associated with familial syndromes like **Gorlin syndrome** (PTCH1 mutation) [1] and **Turcot syndrome** (APC mutation), it is not a feature of Cowden syndrome. * **Astrocytoma:** These are common primary brain tumors but are more typically associated with **Neurofibromatosis type 1 (NF1)** and **Li-Fraumeni syndrome** (TP53). * **PNET:** These aggressive embryonal tumors are not specifically linked to the PTEN mutation or Cowden syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **PTEN Hamartoma Tumor Syndrome (PHTS):** Includes Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome. * **Associated Malignancies:** Patients have a significantly increased risk of **Breast cancer** (most common), **Follicular Thyroid cancer**, and **Endometrial cancer**. * **Mucocutaneous findings:** Trichilemmomas (benign hair follicle tumors) and oral papillomas are hallmark diagnostic features. * **Lhermitte-Duclos Disease** is now considered a Grade I WHO tumor and is often the first clinical sign leading to a Cowden syndrome diagnosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 306-307.

Question 1

Which of the following is involved in the pathogenesis of myasthenia gravis?

Accepted Answer

Autoantibodies against acetylcholine receptors

Answer

Mutation in ryanodine receptors

Answer

Autoantibodies against synaptobrevin

Answer

Autoantibodies against presynaptic calcium channels

Question 2

Which of the following statements is false with respect to demyelinating disorders?

Accepted Answer

Involves biochemical abnormality of myelin

Answer

Increased blood-brain barrier permeability

Answer

More common in females

Answer

Multiple Sclerosis is the most common type of demyelinating disorder

Question 3

Which of the following conditions classically shows a rosette-shaped arrangement of cells?

Accepted Answer

Ependymoma

Answer

Thecoma of ovary

Answer

Neurofibroma

Answer

Lymphoma

Question 4

Rosettes are not seen in which of the following conditions?

Accepted Answer

Neurocysticercosis

Answer

Retinoblastoma

Answer

Medulloblastoma

Answer

Primitive neuroectodermal tumor (PNET)

Question 5

Verocay bodies are seen in which of the following tumors?

Accepted Answer

Schwannoma

Answer

Meningioma

Answer

Glioma

Answer

Medulloblastoma

Question 6

Dumbbell tumors are characteristic of which of the following neoplasms?

Accepted Answer

Neurofibroma

Answer

Meningioma

Answer

Ependymoma

Answer

Thymoma

Question 7

Negri bodies are characteristically seen in which of the following anatomical locations?

Accepted Answer

Hippocampus

Answer

Hypothalamus

Answer

Medulla

Answer

Midbrain

Question 8

Cowden syndrome is associated with which of the following findings?

Accepted Answer

Dysplastic gangliocytoma

Answer

Medulloblastoma

Answer

Astrocytoma

Answer

Primitive neuroectodermal tumor (PNET)

Question 9

Which type of glial cell is commonly found to be malfunctioning in Alzheimer's disease?

Accepted Answer

Microglia

Answer

Radial glia

Answer

Dendrites

Answer

Oligodendrocytes

Question 10

Shearing damage is seen in which of the following organs?

Accepted Answer

Brain

Answer

Heart

Answer

Liver

Answer

Spinal cord

Neuropathology — MCQs

Neuropathology — MCQs

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