Neuroanatomy Practice Questions

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

Cranial Nerve XII. 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)."

Q: What is true about the vestibular nerve?

All of the above.. 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].

Q: 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?

Inhibin. **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).

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

Anterior corticospinal. ### 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].

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

3 weeks. 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.

Q: Which type of bone does not contain Haversian canals?

Spongy bone. 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.

Q: What are the predisposing factors for skin cancer?

Smoking. 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.

Q: Which sign is most pathognomonic of irreversible cell injury?

Amorphous densities in mitochondria. ### 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.

Question 1

The histological feature of shock includes:

Accepted Answer

Acute tubular necrosis (ATN)

Answer

Pulmonary congestion

Answer

Depletion of lipids in adrenal cortex

Answer

Hepatic necrosis

Question 2

Wallenberg's syndrome does not involve which cranial nerve?

Accepted Answer

Cranial Nerve XII

Answer

Cranial Nerve IX

Answer

Cranial Nerve X

Answer

Cranial Nerve XI

Question 3

What is true about the vestibular nerve?

Accepted Answer

All of the above.

Answer

Its nucleus is supplied by the PICA.

Answer

It has an anastomotic connection with the facial nerve.

Answer

The vestibular ganglion is also called Scarpa's ganglion.

Question 4

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?

Accepted Answer

Inhibin

Answer

CA19-9

Answer

CA 50

Answer

Neurospecific enolase

Question 5

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

Accepted Answer

Anterior corticospinal

Answer

Anterior spinocerebellar

Answer

Cuneocerebellar

Answer

Lateral corticospinal

Question 6

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

Accepted Answer

Nasopharyngeal cancer

Answer

Hepatocellular cancer

Answer

Non-small cell carcinoma of lung

Answer

Gastric cancer

Question 7

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

Accepted Answer

3 weeks

Answer

5 weeks

Answer

6 weeks

Answer

2 weeks

Question 8

Which type of bone does not contain Haversian canals?

Accepted Answer

Spongy bone

Answer

Compact bone

Answer

Diaphyseal bone

Answer

Cortical bone

Question 9

What are the predisposing factors for skin cancer?

Accepted Answer

Smoking

Answer

UV light

Answer

Chronic ulcer

Answer

Infrared light

Question 10

Which sign is most pathognomonic of irreversible cell injury?

Accepted Answer

Amorphous densities in mitochondria

Answer

Swelling of the cell membrane

Answer

Ribosomes detached from endoplasmic reticulum

Answer

Clumping of the nucleus

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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