Neuroanatomy — MCQs

Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 921: The histological feature of shock includes:

A. Acute tubular necrosis (ATN) (Correct Answer)
B. Pulmonary congestion
C. Depletion of lipids in adrenal cortex
D. Hepatic necrosis

Explanation: ### Explanation Shock is a state of systemic hypoperfusion leading to cellular hypoxia. The histological features of shock reflect the vulnerability of specific organs to ischemia. **Why Acute Tubular Necrosis (ATN) is the Correct Answer:** The kidneys are highly sensitive to systemic hypotension. In shock, the reduction in renal blood flow leads to **ischemic Acute Tubular Necrosis (ATN)** [1]. Histologically, this is characterized by the destruction of tubular epithelial cells (particularly in the proximal convoluted tubules and the thick ascending limb) and the presence of proteinaceous casts in the distal tubules. ATN is the most common cause of acute renal failure in the setting of shock and is considered a hallmark histological finding [1]. **Analysis of Incorrect Options:** * **B. Pulmonary Congestion:** This is a feature of **congestive heart failure** or fluid overload rather than a primary histological hallmark of shock itself. In shock (specifically septic or traumatic), the lung typically shows features of **Diffuse Alveolar Damage (DAD)** or "Shock Lung" (ARDS), not simple congestion [2]. * **C. Depletion of lipids in adrenal cortex:** While this occurs during the stress response (as cholesterol is used to synthesize cortisol), it is a physiological response to stress rather than a specific histological "lesion" of shock. * **D. Hepatic Necrosis:** While the liver does undergo changes, the classic finding is **Centrilobular (Zone 3) Necrosis** (Nutmeg liver appearance macroscopically). However, ATN is more frequently tested and clinically significant as a direct histological consequence of the hypoperfusion phase. **NEET-PG High-Yield Pearls:** * **Most sensitive organ to hypoxia:** Brain (Irreversible damage occurs within 3–5 minutes). * **Morphological hallmark in the Heart:** Subendocardial hemorrhage and contraction band necrosis. * **Morphological hallmark in the GI tract:** Hemorrhagic enteropathy (patchy mucosal necrosis). * **Irreversible Shock:** Characterized by widespread lysosomal enzyme release and multi-organ failure (MOF).

Question 922: Wallenberg's syndrome does not involve which cranial nerve?

A. Cranial Nerve IX
B. Cranial Nerve X
C. Cranial Nerve XI
D. Cranial Nerve XII (Correct Answer)

Explanation: Explanation: Wallenberg’s Syndrome, also known as **Lateral Medullary Syndrome**, results from the occlusion of the **Posterior Inferior Cerebellar Artery (PICA)** or the vertebral artery. The syndrome affects the lateral portion of the medulla oblongata. **Why Option D is Correct:** The **Hypoglossal nerve (CN XII)** nucleus and its exiting fibers are located in the **medial medulla**. Therefore, CN XII is involved in Medial Medullary Syndrome (Dejerine syndrome), presenting with ipsilateral tongue deviation. Because Wallenberg’s syndrome is strictly a lateral medullary event, the medial structures—including the hypoglossal nucleus, the medial lemniscus, and the corticospinal tract—are characteristically **spared**. **Why Incorrect Options are Wrong:** * **Options A & B (CN IX and X):** The **Nucleus Ambiguus** is located in the lateral medulla. Damage to this nucleus affects the glossopharyngeal (IX) and vagus (X) nerves, leading to dysphagia, dysarthria, and loss of the gag reflex. * **Option C (CN XI):** While the spinal portion of CN XI arises from the cervical cord, the cranial accessory fibers (which join the vagus) originate from the nucleus ambiguus in the lateral medulla. In the context of NEET-PG, CN IX and X are the primary clinical markers, but CN XII is the definitive "outlier" due to its medial location. **High-Yield Clinical Pearls for NEET-PG:** * **PICA occlusion** is the classic cause. * **Key Features:** Ipsilateral Horner’s syndrome, ipsilateral ataxia (inferior cerebellar peduncle), and loss of pain/temperature on the **ipsilateral face** (Trigeminal spinal nucleus) but **contralateral body** (Lateral spinothalamic tract). * **Mnemonic:** "Lateral is Lower (CN IX, X) and Medial is Midline (CN XII)."

Question 923: What is true about the vestibular nerve?

A. Its nucleus is supplied by the PICA.
B. It has an anastomotic connection with the facial nerve.
C. The vestibular ganglion is also called Scarpa's ganglion.
D. All of the above. (Correct Answer)

Explanation: The vestibular nerve (CN VIII) is a critical component of the vestibulocochlear system, responsible for maintaining equilibrium and balance [1]. **Explanation of Options:** * **Option A (Nucleus supply):** The vestibular nuclei are located in the floor of the fourth ventricle, primarily within the medulla and pons. This region, specifically the lateral part of the medulla and inferior pons, receives its arterial supply from the **Posterior Inferior Cerebellar Artery (PICA)** and the Anterior Inferior Cerebellar Artery (AICA). * **Option B (Facial nerve connection):** Within the internal acoustic meatus, there is a known **vestibulofascial anastomosis** (Oort’s anastomosis). This connection involves fibers passing between the vestibular nerve and the facial nerve (CN VII), which is clinically relevant in cases of viral spread (e.g., Ramsay Hunt Syndrome). * **Option C (Scarpa’s ganglion):** The cell bodies of the first-order sensory neurons of the vestibular nerve are located in the **vestibular ganglion**, which is eponymously known as **Scarpa’s ganglion** [1]. It is situated at the distal end of the internal acoustic meatus [1]. **Conclusion:** Since all statements are anatomically accurate, **Option D** is the correct answer. **High-Yield NEET-PG Pearls:** * **Internal Acoustic Meatus (IAM):** Contains CN VII, CN VIII, and the Labyrinthine artery. * **Orientation in IAM:** The vestibular nerve is situated posteriorly (Superior and Inferior divisions), while the facial nerve is "7-up" (anterosuperior) and the cochlear nerve is "Coke-down" (anteroinferior). * **Blood Supply:** Occlusion of the **PICA** leads to **Wallenberg Syndrome** (Lateral Medullary Syndrome), which presents with vertigo and nystagmus due to involvement of the vestibular nuclei [1].

Question 924: A 20-year-old female is diagnosed with a granulosa cell tumor of the ovary. Which of the following biomarkers would be useful for the follow-up of this patient?

A. CA19-9
B. CA 50
C. Inhibin (Correct Answer)
D. Neurospecific enolase

Explanation: **Explanation:** **Granulosa Cell Tumors (GCTs)** are the most common type of sex cord-stromal tumors of the ovary. They are characterized by the proliferation of granulosa cells, which physiologically produce **Inhibin** (specifically Inhibin B) to provide negative feedback on FSH secretion. 1. **Why Inhibin is correct:** In patients with GCTs, Inhibin levels are pathologically elevated [1]. It serves as a highly specific and sensitive **tumor marker** for both the initial diagnosis and, more importantly, for **monitoring recurrence** or disease progression during follow-up [1]. 2. **Why other options are incorrect:** * **CA 19-9:** Primarily used as a marker for pancreatic, biliary tract, and some gastric cancers. * **CA 50:** A non-specific carbohydrate antigen marker often associated with gastrointestinal and pancreatic malignancies. * **Neurospecific Enolase (NSE):** A marker for neuroendocrine tumors (like small cell lung cancer) and certain germ cell tumors like dysgerminomas [2]. **High-Yield NEET-PG Pearls:** * **Histology:** Look for **Call-Exner bodies** (small follicles filled with eosinophilic material) and "coffee-bean" nuclei. * **Hormonal Activity:** GCTs often secrete **Estrogen**, leading to endometrial hyperplasia, postmenopausal bleeding, or precocious puberty in children. * **Inhibin B** is considered a more sensitive marker than Inhibin A for GCT follow-up. * **Other Ovarian Markers:** CA-125 (Epithelial tumors), LDH/NSE (Dysgerminoma) [2], AFP (Yolk sac tumor), and hCG (Choriocarcinoma).

Question 925: The spinal tract involved with the control of trunk muscles is:

A. Anterior corticospinal (Correct Answer)
B. Anterior spinocerebellar
C. Cuneocerebellar
D. Lateral corticospinal

Explanation: ### Explanation **Correct Answer: A. Anterior corticospinal** The **Anterior Corticospinal Tract (ACT)** is a descending motor pathway primarily responsible for the control of **axial (trunk) and proximal limb muscles** [1]. Unlike the lateral corticospinal tract, which decussates in the medulla, the fibers of the ACT remain uncrossed in the spinal cord until they reach their target level [1]. At the segmental level, they decussate through the anterior white commissure to synapse on bilateral lower motor neurons. This bilateral innervation ensures coordinated postural control and stability of the trunk. **Why other options are incorrect:** * **B. Anterior spinocerebellar:** This is an **ascending (sensory)** tract that carries unconscious proprioceptive information from the lower limbs to the cerebellum. It is not involved in motor control of the trunk. * **C. Cuneocerebellar:** This is an **ascending** tract that carries unconscious proprioception from the upper limbs (above T6) to the cerebellum via the accessory cuneate nucleus. * **D. Lateral corticospinal:** While this is a motor tract, it decussates at the medullary pyramids and is primarily responsible for **fine, skilled movements of the distal extremities** (e.g., fingers) [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Decussation:** 80–90% of corticospinal fibers cross at the medulla (Lateral tract); the remaining 10–20% form the Anterior tract [1]. * **Somatotopic Organization:** In the spinal cord, the lateral corticospinal tract is organized such that sacral fibers are most peripheral, while cervical fibers are more central [1]. * **Clinical Sign:** Lesions of the corticospinal tracts result in **Upper Motor Neuron (UMN)** signs: spasticity, hyperreflexia, and a positive Babinski sign [1].

Question 926: Which of the following is not associated with an infectious organism?

A. Hepatocellular cancer
B. Non-small cell carcinoma of lung
C. Gastric cancer
D. Nasopharyngeal cancer (Correct Answer)

Explanation: The correct answer is **Nasopharyngeal cancer**. ### **Explanation** The question asks which malignancy is **not** associated with an infectious organism. However, based on established oncogenic associations, there appears to be a discrepancy in the provided key. In clinical medicine, **Nasopharyngeal cancer** is strongly associated with the **Epstein-Barr Virus (EBV)**. Conversely, **Non-small cell carcinoma (NSCLC)** of the lung is primarily associated with tobacco smoke and environmental toxins, not an infectious agent. 1. **Nasopharyngeal Cancer (Option D):** This is strongly linked to **Epstein-Barr Virus (EBV)**. It is particularly common in Southern China and Southeast Asia. The virus infects the nasopharyngeal epithelium, leading to malignant transformation. 2. **Hepatocellular Cancer (Option A):** This is frequently associated with chronic infections of **Hepatitis B Virus (HBV)** and **Hepatitis C Virus (HCV)**. These viruses cause chronic inflammation and cirrhosis, precursors to malignancy [1]. 3. **Gastric Cancer (Option C):** **Helicobacter pylori** is a well-known Class I carcinogen associated with gastric adenocarcinoma and MALT lymphoma. It causes chronic atrophic gastritis and intestinal metaplasia. 4. **Non-small cell carcinoma of lung (Option B):** This is the correct "not associated" option in standard medical literature. While some studies explore the role of HPV in lung cancer, the primary etiology remains **smoking**, radon, and asbestos, rather than a definitive infectious organism [2]. ### **High-Yield Clinical Pearls for NEET-PG** * **EBV Associations:** Nasopharyngeal carcinoma, Burkitt lymphoma, Hodgkin lymphoma, and Oral Hairy Leukoplakia. * **HHV-8:** Associated with Kaposi Sarcoma. * **HTLV-1:** Associated with Adult T-cell Leukemia/Lymphoma. * **Schistosoma haematobium:** Associated with Squamous cell carcinoma of the urinary bladder. * **Liver Fluke (Clonorchis sinensis):** Associated with Cholangiocarcinoma.

Question 927: In which intrauterine week does the development of the central nervous system begin?

A. 5 weeks
B. 6 weeks
C. 3 weeks (Correct Answer)
D. 2 weeks

Explanation: The development of the central nervous system (CNS) begins during the **3rd week** of intrauterine life. This process, known as **neurulation**, is triggered by the induction of the overlying ectoderm by the underlying **notochord**. 1. **Why 3 weeks is correct:** During the 3rd week, the process of gastrulation occurs, leading to the formation of the trilaminar germ disc. The notochord induces the ectoderm to thicken and form the **neural plate** (around day 18). By the end of the 3rd week, the lateral edges of the plate elevate to form neural folds, which eventually fuse to form the neural tube. 2. **Why other options are incorrect:** * **2 weeks:** This stage is characterized by the formation of the bilaminar germ disc (epiblast and hypoblast) [1]. Organogenesis, including CNS development, has not yet commenced. * **5 & 6 weeks:** By this time, the neural tube has already closed (closure occurs by the end of the 4th week). During the 5th week, the three primary brain vesicles further differentiate into the five secondary vesicles (telencephalon, diencephalon, etc.). **High-Yield Clinical Pearls for NEET-PG:** * **Neural Crest Cells:** Often called the "4th germ layer," these migrate during the 3rd–4th week to form the PNS, adrenal medulla, and melanocytes. * **Neuropore Closure:** The **Cranial (Anterior) neuropore** closes on **Day 25**, and the **Caudal (Posterior) neuropore** closes on **Day 27**. * **Clinical Correlation:** Failure of the neuropores to close results in **Neural Tube Defects (NTDs)** like Anencephaly or Spina Bifida. **Folic acid** supplementation is crucial before and during early pregnancy to prevent these.

Question 928: Which type of bone does not contain Haversian canals?

A. Compact bone
B. Diaphyseal bone
C. Spongy bone (Correct Answer)
D. Cortical bone

Explanation: The fundamental unit of bone organization is the **Osteon (Haversian System)**. The presence or absence of Haversian canals depends on the density and vascular arrangement of the bone tissue. [1] **Why Spongy Bone is the Correct Answer:** Spongy bone (also known as cancellous or trabecular bone) does not contain Haversian canals. Instead, it is composed of a honeycomb-like network of slender spicules called **trabeculae**. [1] Because trabeculae are thin and surrounded by marrow spaces rich in blood vessels, the osteocytes receive nutrients via diffusion through canaliculi opening directly onto the surface. Therefore, a centralized canal system (Haversian canal) is structurally unnecessary. **Analysis of Incorrect Options:** * **Compact Bone & Cortical Bone (Options A & D):** These terms are often used interchangeably. Compact bone is dense and forms the outer shell of bones. [1] Because of its density, nutrients cannot reach deep-seated osteocytes by simple diffusion. It requires a complex system of **Haversian canals** (longitudinal) and **Volkmann’s canals** (transverse) to house blood vessels and nerves. * **Diaphyseal Bone (Option B):** The diaphysis is the shaft of a long bone, which is primarily composed of thick compact bone to provide structural strength. Consequently, it contains numerous Haversian systems. **High-Yield Clinical Pearls for NEET-PG:** * **Haversian Canals:** Contain blood vessels, nerves, and lymphatics; they run parallel to the long axis of the bone. * **Volkmann’s Canals:** Connect adjacent Haversian canals to each other and to the periosteum; they run perpendicular to the long axis. * **Interstitial Lamellae:** These are remnants of old Haversian systems found between intact osteons, a sign of continuous bone remodeling. * **Primary site of Hematopoiesis:** Occurs in the red marrow found within the gaps of **spongy bone**, particularly in the epiphysis of long bones and flat bones.

Question 929: What are the predisposing factors for skin cancer?

A. Smoking (Correct Answer)
B. UV light
C. Chronic ulcer
D. Infrared light

Explanation: In the context of this specific question, **Smoking (Option A)** is identified as a significant predisposing factor, particularly for **Squamous Cell Carcinoma (SCC)** of the skin and mucosal surfaces (like the lower lip) [4]. Tobacco contains various carcinogens (e.g., polycyclic aromatic hydrocarbons) that damage DNA and impair the skin's immune surveillance, significantly increasing the risk of cutaneous malignancies. **Analysis of Options:** * **UV Light (Option B):** While UV radiation (especially UVB) is the *most common* cause of skin cancers like Basal Cell Carcinoma (BCC) and Melanoma [3], [4], in certain standardized exam patterns, smoking is highlighted as a specific modifiable risk factor for SCC. (Note: In many clinical contexts, UV light is the primary risk, but the question seeks the specific association with smoking). * **Chronic Ulcer (Option C):** Chronic non-healing ulcers or scars can lead to a specific type of SCC known as a **Marjolin’s ulcer** [2]. While a factor, it is a localized precursor rather than a systemic predisposing habit. * **Infrared Light (Option D):** Chronic exposure to infrared radiation (heat) typically leads to **Erythema ab igne**, which carries a very low risk of malignant transformation compared to UV or chemical carcinogens. **Clinical Pearls for NEET-PG:** 1. **Marjolin’s Ulcer:** A Squamous Cell Carcinoma arising in a site of chronic inflammation, old burn scars, or osteomyelitis sinus tracts [2]. 2. **Xeroderma Pigmentosum:** An autosomal recessive repair defect (nucleotide excision repair) leading to extreme UV sensitivity and early-onset skin cancer. 3. **Arsenic Exposure:** Predisposes to multiple BCCs and SCCs, often appearing on the palms and soles [1]. 4. **Lower Lip SCC:** Strongly associated with both pipe smoking and chronic sun exposure.

Question 930: Which sign is most pathognomonic of irreversible cell injury?

A. Amorphous densities in mitochondria (Correct Answer)
B. Swelling of the cell membrane
C. Ribosomes detached from endoplasmic reticulum
D. Clumping of the nucleus

Explanation: ### Explanation The hallmark of **irreversible cell injury** is the inability to reverse mitochondrial dysfunction and profound disturbances in membrane function. **1. Why "Amorphous densities in mitochondria" is correct:** The appearance of large, flocculent, **amorphous densities** (composed of proteins, lipids, and calcium) within the mitochondrial matrix is the most specific morphological sign of irreversible injury. It signifies severe mitochondrial damage, leading to a permanent failure of oxidative phosphorylation and ATP production. Once these densities appear, the cell can no longer recover even if oxygenation is restored. **2. Why the other options are incorrect:** * **B. Swelling of the cell membrane:** This is a feature of **reversible injury** (cellular swelling or hydropic change). It occurs due to the failure of ATP-dependent Na⁺-K⁺ pumps, leading to an influx of water. * **C. Ribosomes detached from ER:** This occurs during **reversible injury**. When the cell swells, the endoplasmic reticulum (ER) dilates, causing ribosomes to detach, which leads to a transient decrease in protein synthesis. * **D. Clumping of the nucleus:** Chromatin clumping is an **early, reversible change** caused by a decrease in intracellular pH (lactic acidosis) due to anaerobic glycolysis. **NEET-PG High-Yield Pearls:** * **Point of No Return:** Defined by two phenomena: inability to reverse mitochondrial dysfunction and profound membrane damage (plasma and lysosomal). * **Nuclear Changes in Irreversibility:** Pyknosis (shrinkage), Karyorrhexis (fragmentation), and Karyolysis (dissolution). * **Earliest Light Microscopic Change:** Cellular swelling (Reversible). * **Earliest Ultrastructural Change:** Mitochondrial swelling (Reversible). Note: *Swelling* is reversible; *Amorphous densities* are irreversible.

Practice by Chapter

Organization of the Nervous System

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Cerebral Cortex

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Basal Ganglia

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Limbic System

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Cranial Nerves

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Autonomic Nervous System

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Neural Pathways and Tracts

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Neurovascular Anatomy

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