Neuroanatomy — MCQs

Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 831: Which of the following is NOT a cause of granular contracted kidney?

A. Benign nephrosclerosis
B. Diabetes mellitus (Correct Answer)
C. Chronic pyelonephritis
D. Chronic glomerulonephritis

Explanation: **Explanation** The term **"Granular Contracted Kidney"** refers to a kidney that has become shrunken, firm, and possesses a rough, pebbly surface due to chronic parenchymal scarring and interstitial fibrosis. **Why Diabetes Mellitus is the Correct Answer:** In **Diabetes Mellitus**, the kidneys typically undergo **enlargement** (hypertrophy) in the early stages due to hyperfiltration [1]. In advanced Diabetic Nephropathy (Kimmelstiel-Wilson disease), while the kidneys may eventually scar, they characteristically **remain normal in size or are enlarged** and have a **smooth surface**, rather than a granular contracted one [2]. This is a classic radiological and pathological distinction used in exams. **Analysis of Other Options:** * **Benign Nephrosclerosis:** Caused by long-standing hypertension, leading to hyaline arteriolosclerosis. This results in diffuse ischemia, producing a symmetrical, finely granular "leather-grain" appearance. * **Chronic Pyelonephritis:** Characterized by irregular, asymmetric contraction with coarse, U-shaped scars over dilated calyces. This is a classic cause of a contracted kidney. * **Chronic Glomerulonephritis:** Represents the end-stage of various glomerular diseases. It leads to symmetrical, diffuse destruction of nephrons, resulting in small, contracted kidneys with a finely granular surface. **NEET-PG High-Yield Pearls:** * **Large Kidneys in Renal Failure:** Usually, chronic renal failure (CRF) presents with small kidneys. Exceptions (Large/Normal kidneys in CRF) include **Diabetes**, **Amyloidosis**, **Polycystic Kidney Disease (PKD)**, and **Multiple Myeloma**. * **Fine Granularity:** Seen in Benign Nephrosclerosis and Chronic Glomerulonephritis. * **Coarse Granularity/Scars:** Seen in Chronic Pyelonephritis. * **Fleabitten Kidney:** Seen in Malignant Hypertension and Bacterial Endocarditis.

Question 832: Which of the following is NOT a feature of AIDS-related lymphadenopathy?

A. Florid reactive hyperplasia
B. Follicle lysis
C. Haematoxylin bodies (Correct Answer)
D. Collection of monocytoid B cells in sinuses

Explanation: **Explanation:** The question asks for the feature **not** associated with AIDS-related lymphadenopathy. **Correct Option: C. Haematoxylin bodies** Haematoxylin bodies (also known as Gross bodies) are rounded, amorphous, lilac-colored structures found in the heart, kidneys, or lymph nodes. They represent denatured nuclear material coated with antibodies and are a **pathognomonic feature of Systemic Lupus Erythematosus (SLE)**, not HIV/AIDS. **Analysis of Incorrect Options (Features of AIDS Lymphadenopathy):** The lymph node changes in HIV progress through stages known as **PGL (Persistent Generalized Lymphadenopathy)**: * **Option A (Florid reactive hyperplasia):** This is the hallmark of the early stage of HIV infection, where HIV preferentially targets CD4+ cells, leading to eventual lymphocyte depletion [1]. Lymph nodes show massive, irregularly shaped germinal centers. * **Option B (Follicle lysis):** This is a characteristic finding where small lymphocytes from the mantle zone "invade" and break up the germinal centers (the "moth-eaten" appearance). It signifies the transition toward follicular involution. * **Option D (Monocytoid B cells):** In the early stages of HIV, there is often a prominent proliferation of monocytoid B cells within the subcapsular and trabecular sinuses. **NEET-PG High-Yield Pearls:** 1. **Stages of HIV Lymphadenopathy:** Hyperplasia (Stage I) → Follicle Lysis (Stage II) → Follicular Involution/Depletion (Stage III) [1]. 2. **Warthin-Finkeldey Giant Cells:** While classically associated with Measles, these can also be seen in the hyperplastic lymph nodes of HIV patients. 3. **Castleman Disease:** HIV-positive patients have an increased risk of the multicentric variant of Castleman disease, often associated with HHV-8.

Question 833: The geniculate ganglion is associated with which function?

A. Lacrimation
B. Taste sensation (Correct Answer)
C. Salivation
D. Sweating

Explanation: **Explanation:** The **Geniculate Ganglion** is the sensory ganglion of the **Facial Nerve (CN VII)**, located in the facial canal of the temporal bone. It contains the cell bodies of pseudo-unipolar neurons responsible for two primary sensory functions: **taste sensation** from the anterior two-thirds of the tongue (via the chorda tympani) and general somatic sensation from the external auditory canal. **Why Option B is Correct:** Taste fibers from the anterior 2/3 of the tongue travel via the chorda tympani to join the facial nerve [1]. The cell bodies for these special visceral afferent (SVA) fibers are located in the geniculate ganglion. From here, fibers project to the *nucleus tractus solitarius* in the medulla. **Analysis of Incorrect Options:** * **A & C (Lacrimation & Salivation):** These are parasympathetic (secretomotor) functions. While the preganglionic fibers pass *through* the geniculate ganglion, they **do not synapse** there. Lacrimation involves the Pterygopalatine ganglion, and salivation (submandibular/sublingual) involves the Submandibular ganglion. * **D (Sweating):** This is a sympathetic function. Facial sweating is mediated by postganglionic sympathetic fibers arising from the Superior Cervical Ganglion, traveling along the external carotid artery plexus. **High-Yield Clinical Pearls for NEET-PG:** * **Ramsay Hunt Syndrome:** Herpes Zoster infection involving the geniculate ganglion, presenting with facial palsy and vesicles in the external auditory canal/auricle. * **Nerve of Pterygoid Canal (Vidian Nerve):** Formed by the junction of the Great Petrosal Nerve (branch from geniculate ganglion) and Deep Petrosal Nerve. * **First branch of CN VII:** The Greater Petrosal Nerve arises directly from the geniculate ganglion.

Question 834: Which region begins the closure of the neural tube?

A. Cranial end
B. Caudal end
C. Cervical region (Correct Answer)
D. Lumbar region

Explanation: **Explanation:** The formation of the neural tube (neurulation) occurs during the 4th week of development. The process begins when the neural folds elevate and fuse in the midline. This fusion does not occur simultaneously along the entire length of the embryo; instead, it initiates in the **cervical region** (specifically at the level of the 5th somite). From this starting point, the closure proceeds like a "zipper" in both cranial and caudal directions. **Analysis of Options:** * **Cervical region (Correct):** This is the primary site of initial fusion. By the end of the 3rd week/start of the 4th week, the neural folds meet here first. * **Cranially (Incorrect):** While closure proceeds toward the head, the cranial end (Anterior Neuropore) is actually one of the last parts to close (around Day 25). * **Caudally (Incorrect):** Similarly, the caudal end (Posterior Neuropore) closes after the cervical and cervical regions, typically around Day 27-28 [1]. * **Lumbar region (Incorrect):** This region is located near the caudal end and is one of the final areas to undergo primary neurulation. **High-Yield Clinical Pearls for NEET-PG:** * **Neuropore Closure:** Anterior neuropore closes on **Day 25** (failure leads to Anencephaly); Posterior neuropore closes on **Day 27-28** [1]. * **Folic Acid:** Supplementation (400 mcg/day) is critical pre-conception to prevent Neural Tube Defects (NTDs) by ensuring proper closure. * **Alpha-Fetoprotein (AFP):** Elevated levels in maternal serum or amniotic fluid are a key screening marker for open NTDs [1].

Question 835: Which of the following is not a cyclin-dependent kinase (CDK) inhibitor?

A. p21
B. p27
C. p53 (Correct Answer)
D. p57

Explanation: **Explanation:** The cell cycle is strictly regulated by **Cyclin-Dependent Kinases (CDKs)** and their inhibitors (CKIs). CKIs are categorized into two families: the **Cip/Kip family** (p21, p27, p57) and the **INK4 family** (p15, p16, p18, p19). **Why p53 is the Correct Answer:** **p53** is a **tumor suppressor protein**, often called the "Guardian of the Genome." It is not a direct CDK inhibitor itself [1]. Instead, it acts as a transcription factor. When DNA damage occurs, p53 levels rise and trigger the transcription of **p21**, which then binds to and inhibits CDK complexes to arrest the cell cycle [1]. Thus, while p53 *regulates* inhibitors, it does not belong to the biochemical class of CDK inhibitors. **Analysis of Incorrect Options:** * **p21 (Cip1):** A potent CDK inhibitor induced by p53. it inhibits a wide range of CDK-cyclin complexes (especially CDK2), leading to cell cycle arrest in the G1 phase. * **p27 (Kip1):** Responds to growth inhibitory signals (like TGF-β). It binds to and inhibits Cyclin E-CDK2 and Cyclin D-CDK4 complexes. * **p57 (Kip2):** A member of the Cip/Kip family primarily involved in embryogenesis. Mutations in the p57 gene are associated with **Beckwith-Wiedemann syndrome**. **High-Yield NEET-PG Pearls:** * **INK4 Family:** Specifically inhibits **CDK4 and CDK6** (involved in G1 progression). * **p16:** A member of the INK4 family; its expression is a marker for HPV-related cervical and oropharyngeal cancers. * **Rb Protein:** The "molecular brake" of the cell cycle; when phosphorylated by CDKs, it releases E2F to allow S-phase entry [1]. p53 and Rb are the two most commonly mutated genes in human cancers.

Question 836: Which Brodmann area corresponds to the premotor cortex?

A. Area 6 (Correct Answer)
B. Area 7
C. Area 8
D. Area 12

Explanation: The **Premotor Cortex** is located in the posterior part of the frontal lobe, immediately anterior to the primary motor cortex (Area 4) [1]. It corresponds to **Brodmann Area 6** [1]. **1. Why Area 6 is Correct:** Area 6 is divided into the **Premotor Cortex** (lateral surface) and the **Supplementary Motor Area** (medial surface) [1]. Its primary function is the planning and sequencing of complex movements and the regulation of posture [1]. It receives sensory input from the posterior parietal cortex and sends signals to the primary motor cortex to execute voluntary actions [2]. **2. Analysis of Incorrect Options:** * **Area 7:** Located in the **Superior Parietal Lobule** [3]. It is a sensory association area involved in visuospatial processing and hand-eye coordination [3]. * **Area 8:** Located anterior to Area 6, it contains the **Frontal Eye Field (FEF)**. It controls conjugate voluntary scanning movements of the eyes to the opposite side. * **Area 12:** Located on the orbitofrontal surface of the frontal lobe. It is part of the **Prefrontal Cortex**, involved in executive functions and emotional regulation. **High-Yield Clinical Pearls for NEET-PG:** * **Lesion of Area 6:** Results in **Apraxia** (inability to perform learned purposeful movements despite having normal muscle power). * **Lesion of Area 8:** Causes the eyes to deviate **towards** the side of the lesion (due to unopposed action of the opposite FEF). * **Jacksonian March:** Typically originates in Area 4 (Primary Motor Cortex), but Area 6 contributes to the refinement of these motor outputs. * **Giant Pyramidal Cells (Betz cells):** These are characteristic of Area 4, whereas Area 6 lacks these large cells.

Question 837: Which virus is associated with Hodgkin's lymphoma?

A. EBV (Epstein-Barr virus) (Correct Answer)
B. CMV (Cytomegalovirus)
C. HHV6 (Human herpesvirus 6)
D. HHV8 (Human herpesvirus 8)

Explanation: **Explanation:** The correct answer is **EBV (Epstein-Barr virus)**. Epstein-Barr virus (Human Gammaherpesvirus 4) is a potent oncogenic virus with a strong tropism for B-lymphocytes. In the pathogenesis of **Hodgkin’s Lymphoma (HL)**, EBV is found in approximately 40-50% of cases (particularly the Mixed Cellularity subtype). The virus expresses the **LMP-1 (Latent Membrane Protein-1)** oncogene, which mimics CD40 signaling, activating the NF-κB and JAK/STAT pathways. This promotes the survival and proliferation of the characteristic **Reed-Sternberg cells**. **Analysis of Incorrect Options:** * **CMV (Cytomegalovirus):** While a member of the Herpesviridae family, it is primarily associated with congenital infections and infectious mononucleosis-like syndromes in immunocompromised patients, not lymphomas. * **HHV-6:** This virus causes Roseola Infantum (Exanthema Subitum). Although it can remain latent in T-cells, it has no established causative link to Hodgkin’s Lymphoma. * **HHV-8:** Also known as KSHV, this virus is specifically associated with **Kaposi Sarcoma**, Primary Effusion Lymphoma (PEL), and Multicentric Castleman Disease, but not classic Hodgkin’s Lymphoma. **High-Yield Clinical Pearls for NEET-PG:** * **EBV Associations:** Burkitt Lymphoma (t(8;14)), Nasopharyngeal Carcinoma, Oral Hairy Leukoplakia (in HIV), and Post-transplant Lymphoproliferative Disorder (PTLD). * **HL Subtypes:** EBV is most commonly associated with the **Mixed Cellularity** subtype and least commonly with the Lymphocyte Predominant subtype. * **Reed-Sternberg Cells:** Look for "Owl’s eye" appearance; these cells are typically **CD15+ and CD30+** (except in the Nodular Lymphocyte Predominant variant).

Question 838: What is the investigation of choice in the early phase of renal transplant?

A. X-ray
B. Intravenous pyelogram (IVP)
C. CT scan
D. Ultrasonography (Correct Answer)

Explanation: **Explanation:** **Ultrasonography (USG)**, specifically with **Color Doppler**, is the investigation of choice in the early post-operative phase of a renal transplant [1]. Its primary utility lies in its ability to non-invasively assess both the anatomical integrity and the vascular status of the graft at the bedside. **Why Ultrasonography is the Correct Choice:** 1. **Vascular Assessment:** It is the gold standard for detecting early vascular complications such as renal artery thrombosis or renal vein thrombosis. 2. **Perigraft Collections:** It easily identifies early surgical complications like hematomas, urinomas, or lymphoceles [1]. 3. **Non-Nephrotoxic:** Unlike CT or IVP, it does not require contrast agents, which is critical since early graft function may be suboptimal. **Why Other Options are Incorrect:** * **X-ray:** Provides no information regarding soft tissue status, vascularity, or acute graft dysfunction. * **Intravenous Pyelogram (IVP):** Requires iodinated contrast, which is **nephrotoxic**. It is contraindicated in the early phase where the graft is vulnerable to acute tubular necrosis (ATN) or rejection. * **CT Scan:** While useful for complex anatomy, standard CT lacks the real-time hemodynamic data provided by Doppler. Contrast-enhanced CT (CECT) carries a high risk of contrast-induced nephropathy in a newly transplanted kidney. **High-Yield Clinical Pearls for NEET-PG:** * **Resistive Index (RI):** A high RI (>0.8) on Doppler is a sensitive (though non-specific) indicator of graft dysfunction, often seen in acute rejection or ATN. * **Urinoma vs. Lymphocele:** Urinomas typically appear within the first 1–2 weeks; lymphoceles usually appear later (2–6 weeks post-op). * **Gold Standard for Rejection:** While USG is the initial screening tool, **Renal Biopsy** remains the definitive gold standard for diagnosing graft rejection [1].

Question 839: Oil red O staining is used for which type of specimen preparation?

A. Frozen section (Correct Answer)
B. Glutaraldehyde fixed specimen
C. Alcohol fixed specimen
D. Formalin fixed specimen

Explanation: **Explanation:** **Oil Red O** is a lysochrome (fat-soluble) dye used for the histological visualization of **lipids** (triglycerides and neutral fats) in tissue sections. **Why Frozen Section is Correct:** The fundamental principle of lipid staining is that the lipids must remain preserved within the tissue. In standard paraffin embedding, tissues undergo dehydration with **alcohol** and clearing with **xylene**. These organic solvents dissolve lipids, leaving behind empty vacuoles (as seen in adipocytes on H&E stains). To prevent this loss, the tissue must be processed using **frozen sections** (cryostat), which bypasses the use of lipid-dissolving organic solvents, thereby keeping the fat droplets intact for the dye to color. **Why Other Options are Incorrect:** * **B, C, & D:** Glutaraldehyde, Alcohol, and Formalin-fixed specimens are typically processed for paraffin embedding. Alcohol, in particular, is a potent lipid solvent. While formalin-fixed tissue can technically be used if cut on a freezing microtome, the standard "specimen preparation" required for successful Oil Red O staining in a clinical or exam context is the **frozen section**. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Application:** Oil Red O is used to diagnose **Fat Embolism Syndrome** (identifying fat globules in lung tissue or sputum) and to identify lipid-laden macrophages in **Atherosclerosis**. * **Other Lipid Stains:** Sudan Black B (stains myelin and phospholipids) and Osmium Tetroxide. * **Staining Result:** Lipids appear **bright red**, while nuclei (if counterstained with Hematoxylin) appear blue/black. * **Neuroanatomy Link:** It is used to demonstrate myelin breakdown products in Wallerian degeneration.

Question 840: Which of the following is NOT a function of the rough endoplasmic reticulum?

A. Protein synthesis
B. Protein folding
C. Degradation of misfolded proteins
D. Steroid synthesis (Correct Answer)

Explanation: The **Rough Endoplasmic Reticulum (RER)** is characterized by the presence of ribosomes on its surface, making it the primary site for the synthesis and processing of proteins destined for secretion, membrane integration, or lysosomal enzymes [1]. **Why Steroid Synthesis is the Correct Answer:** Steroid synthesis is a primary function of the **Smooth Endoplasmic Reticulum (SER)**, not the RER. The SER lacks ribosomes and contains enzymes (like cytochrome P450) necessary for lipid metabolism, steroid hormone production (e.g., in the adrenal cortex and gonads), and detoxification of drugs/toxins (e.g., in the liver) [3]. **Analysis of Incorrect Options:** * **Protein Synthesis:** This is the hallmark function of RER. Ribosomes attached to the RER translate mRNA into polypeptide chains [1], [2]. * **Protein Folding:** After synthesis, the RER provides a specialized environment for proteins to achieve their native 3D conformation, assisted by molecular chaperones like BiP. * **Degradation of Misfolded Proteins:** The RER is central to "Quality Control." Misfolded proteins are identified and exported back to the cytosol for degradation via the **ER-associated degradation (ERAD)** pathway and the ubiquitin-proteasome system. **High-Yield Clinical Pearls for NEET-PG:** * **Nissl Bodies:** In neurons, the RER is seen as Nissl bodies (found in the soma and dendrites, but **absent in the axon hillock** and axon). * **Organelle Distribution:** RER is abundant in protein-secreting cells (e.g., Pancreatic acinar cells, Plasma cells), while SER is abundant in steroid-secreting cells (e.g., Leydig cells) and the liver [1]. * **Sarcoplasmic Reticulum:** A specialized form of SER in muscle cells responsible for calcium sequestration.

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