Brain and Neuroanatomy — MCQs

Brain and Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 151: Cerebellar cortex contains which of the following cells?

A. Pyramidal cells
B. Purkinje cells (Correct Answer)
C. Stromal cells
D. Kupffer cells

Explanation: ### Explanation **Correct Option: B. Purkinje cells** The cerebellar cortex is organized into three distinct histological layers. From superficial to deep, these are the **Molecular layer**, the **Purkinje cell layer**, and the **Granular layer** [2]. * **Purkinje cells** are the functional units of the cerebellum [1]. They are large, flask-shaped neurons whose extensive dendrites fan out into the molecular layer, while their axons provide the **sole output** from the cerebellar cortex to the deep cerebellar nuclei [1]. They are primarily inhibitory (GABAergic) [2]. **Analysis of Incorrect Options:** * **A. Pyramidal cells:** These are the hallmark neurons of the **cerebral cortex** (specifically layers III and V) and the hippocampus [3]. They are excitatory neurons and are not found in the cerebellum. * **C. Stromal cells:** These are connective tissue cells that form the structural framework of various organs (like the bone marrow or ovaries). The central nervous system lacks traditional stroma; its support framework is provided by **neuroglia**. * **D. Kupffer cells:** These are specialized macrophages located in the **liver sinusoids**, forming part of the reticuloendothelial system. **High-Yield Facts for NEET-PG:** * **Layers of Cerebellar Cortex:** Remember the mnemonic **M-P-G** (Molecular, Purkinje, Granular). * **Cell Types:** The Granular layer contains **Granule cells** (the most numerous neurons in the brain) and **Golgi cells** [2]. The Molecular layer contains **Stellate** and **Basket cells** [2]. * **Afferent Fibers:** All afferent inputs to the cerebellum are excitatory. **Climbing fibers** (from the inferior olive) synapse directly on Purkinje cells, while **Mossy fibers** synapse on Granule cells [2]. * **Clinical Correlation:** Damage to Purkinje cells often results in **ipsilateral ataxia**, hypotonia, and dysmetria.

Question 152: Which of the following is NOT a common site for intracranial aneurysms?

A. Posterior inferior cerebellar artery (Correct Answer)
B. Bifurcation of the middle cerebral artery (MCA)
C. Junction of the internal carotid artery (ICA) and posterior communicating artery
D. Anterior communicating artery

Explanation: **Explanation:** Intracranial (berry) aneurysms typically occur at the **bifurcations or junctions** of the arteries within the **Circle of Willis**, where hemodynamic stress is highest due to turbulent blood flow and structural weakness in the tunica media [1]. **1. Why Option A is the Correct Answer:** While aneurysms can occur in the posterior circulation, the **Posterior Inferior Cerebellar Artery (PICA)** is a much less common site compared to the anterior circulation. Statistically, approximately **85-90%** of berry aneurysms are found in the anterior part of the Circle of Willis [1]. PICA involvement is more frequently associated with specific clinical syndromes (like Wallenberg syndrome) or dissections rather than being a primary "common" site for berry aneurysms. **2. Analysis of Incorrect Options (Common Sites):** * **Anterior Communicating Artery (Option D):** This is the **most common** overall site (approx. 30-35%) for intracranial aneurysms [1]. * **ICA and Posterior Communicating Junction (Option C):** This is the **second most common** site (approx. 30-35%). Aneurysms here are high-yield because they often present with **ipsilateral 3rd nerve palsy** (mydriasis and ptosis). * **MCA Bifurcation (Option B):** This is the third most common site (approx. 20%). These are clinically significant as they are more likely to cause intracerebral hemorrhage into the Sylvian fissure. **Clinical Pearls for NEET-PG:** * **Risk Factors:** Polycystic Kidney Disease (ADPKD), Ehlers-Danlos syndrome, and Coarctation of the Aorta are strongly associated with berry aneurysms. * **Presentation:** Rupture leads to **Subarachnoid Hemorrhage (SAH)**, classically described as the "worst headache of my life" (Thunderclap headache) [2]. * **Diagnosis:** Non-contrast CT is the initial investigation; Digital Subtraction Angiography (DSA) is the gold standard for localization [3].

Question 153: Which of the following is NOT a constituent of the inferior cerebellar peduncle?

A. Anterior spinocerebellar tract (Correct Answer)
B. Cuneocerebellar tract
C. Olivocerebellar fibers
D. Paraolivary nucleus fibers

Explanation: The **Inferior Cerebellar Peduncle (ICP)**, also known as the restiform body, primarily connects the medulla oblongata to the cerebellum. It contains both afferent and efferent fibers, but the majority are afferent. ### Why Option A is Correct The **Anterior Spinocerebellar Tract (ASCT)** is the exception. Unlike most spinocerebellar fibers, the ASCT ascends to the level of the midbrain and enters the cerebellum through the **Superior Cerebellar Peduncle (SCP)**. It is unique because it "double crosses"—once in the spinal cord and again within the cerebellum—to provide information about whole-limb movements. ### Analysis of Incorrect Options * **B. Cuneocerebellar tract:** These fibers carry unconscious proprioception from the upper limbs (above T6) and enter via the ICP. * **C. Olivocerebellar fibers:** These are the largest component of the ICP [1]. They originate from the contralateral inferior olivary nucleus and terminate as **climbing fibers** in the cerebellar cortex [1]. * **D. Paraolivary nucleus fibers:** These (along with the accessory olivary nuclei) contribute to the olivocerebellar system and pass through the ICP [1]. ### High-Yield NEET-PG Pearls * **Mnemonic for ICP Constituents:** "Always Take My Dog Outside" (plus others) * **A**rcuate fibers (External) * **T**rigeminocerebellar tract * **M**argin of the 4th ventricle * **D**orsal (Posterior) spinocerebellar tract * **O**livocerebellar tract (Climbing fibers) [1] * *Also: Vestibulocerebellar and Cuneocerebellar tracts.* * **Clinical Correlation:** Damage to the ICP (often seen in **Wallenberg Syndrome/Lateral Medullary Syndrome**) leads to ipsilateral cerebellar ataxia. * **The Rule of Three:** Remember that the **Middle Cerebellar Peduncle** is the largest and contains *only* afferent fibers (Pontocerebellar).

Question 154: Which of the following is NOT a paired venous sinus?

A. Superior petrosal sinus
B. Inferior petrosal sinus
C. Superior sagittal sinus (Correct Answer)
D. Transverse sinus

Explanation: The dural venous sinuses are endothelium-lined channels located between the periosteal and meningeal layers of the dura mater. They are categorized into **paired** and **unpaired** sinuses. [1] **1. Why Superior Sagittal Sinus is the Correct Answer:** The **Superior Sagittal Sinus (SSS)** is an **unpaired** sinus. It runs along the superior attached border of the falx cerebri, beginning at the crista galli and terminating at the internal occipital protuberance (confluence of sinuses). Because it is a midline structure, it does not have a bilateral counterpart. **2. Analysis of Incorrect Options (Paired Sinuses):** * **Superior Petrosal Sinus:** Paired. It runs along the superior border of the petrous temporal bone, connecting the cavernous sinus to the transverse sinus. * **Inferior Petrosal Sinus:** Paired. It drains the cavernous sinus into the internal jugular vein through the jugular foramen. * **Transverse Sinus:** Paired. These run laterally from the confluence of sinuses along the attachment of the tentorium cerebelli. **High-Yield NEET-PG Clinical Pearls:** * **Unpaired Sinuses:** Superior sagittal, Inferior sagittal, Straight, Occipital, and Anterior/Posterior intercavernous sinuses. [1] * **Paired Sinuses:** Cavernous, Superior petrosal, Inferior petrosal, Transverse, Sigmoid, and Sphenoparietal sinuses. * **The Confluence of Sinuses (Torcular Herophili):** The meeting point of the Superior Sagittal, Straight, and Occipital sinuses. * **Clinical Correlation:** Obstruction of the Superior Sagittal Sinus (e.g., via thrombosis) can lead to bilateral hemorrhagic infarcts due to impaired venous drainage of the cerebral hemispheres. [1]

Question 155: A person has inability to look downward and laterally. Which nerve is injured?

A. Oculomotor
B. Trochlear (Correct Answer)
C. Abducent
D. Trigeminal

Explanation: **Explanation:** The correct answer is **Trochlear Nerve (CN IV)**. This nerve provides motor innervation to a single muscle: the **Superior Oblique (SO)**. 1. **Why Trochlear is Correct:** The primary action of the Superior Oblique muscle is **depression** (looking down) and **intorsion**. However, its ability to depress the eye is maximal when the eye is adducted (looking medially). When testing the nerve clinically, the patient is asked to look **downward and laterally** (or medially depending on the clinical test context, but functionally, the SO is the only muscle that can depress the eye while in an adducted position) [1]. A lesion results in vertical diplopia, and patients often tilt their head to the opposite side to compensate. 2. **Why Incorrect Options are Wrong:** * **Oculomotor (CN III):** Supplies the Superior, Inferior, and Medial Recti, and the Inferior Oblique [1]. Injury would cause "Down and Out" positioning due to the unopposed action of the Lateral Rectus and Superior Oblique, along with ptosis and mydriasis. * **Abducent (CN VI):** Supplies the **Lateral Rectus** [1]. Injury results in an inability to abduct the eye (look laterally), leading to medial strabismus. * **Trigeminal (CN V):** This is primarily a sensory nerve for the face and motor nerve for muscles of mastication; it does not control extraocular eye movements. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** **LR6SO4** (Lateral Rectus by CN VI, Superior Oblique by CN IV, all others by CN III). * The Trochlear nerve is the **thinnest** cranial nerve and the only one to exit from the **dorsal aspect** of the brainstem. * It has the longest intracranial course, making it highly susceptible to trauma.

Question 156: The hypoglossal nucleus is located in which part of the brainstem?

A. Midbrain
B. Pons
C. Medulla (Correct Answer)
D. Lower pons

Explanation: **Explanation:** The **hypoglossal nucleus** is a motor nucleus that gives rise to the **Hypoglossal nerve (CN XII)**. It is located in the **Medulla Oblongata**, specifically in the floor of the fourth ventricle. On the dorsal surface of the open medulla, it creates a visible elevation known as the **hypoglossal triangle**, situated medial to the vagal triangle. **Why the other options are incorrect:** * **Midbrain:** This region contains the nuclei for the Oculomotor (CN III) and Trochlear (CN IV) nerves. * **Pons:** The main nuclei located here are the Trigeminal (CN V), Abducens (CN VI), Facial (CN VII), and Vestibulocochlear (CN VIII) nuclei. [1] * **Lower Pons:** While the Abducens and Facial nuclei are located in the lower pons, the Hypoglossal nucleus remains strictly within the medullary territory. [1] **Clinical Pearls & High-Yield Facts for NEET-PG:** 1. **Functional Component:** The hypoglossal nucleus is classified as **GSE (General Somatic Efferent)** because it supplies the muscles of the tongue (except the Palatoglossus, which is supplied by the Pharyngeal plexus/CN X). 2. **Blood Supply:** It is supplied by the **Paramedian branches of the Vertebral artery**. 3. **Medial Medullary Syndrome (Dejerine Syndrome):** An infarct here involves the hypoglossal nerve fibers, leading to **ipsilateral paralysis and atrophy of the tongue**, with the tongue deviating toward the side of the lesion upon protrusion. 4. **Rule of 4:** Cranial nerves IX, X, XI, and XII are all associated with the Medulla. [1]

Question 157: Which of the following arteries supplies blood to the trigeminal ganglion?

A. Basilar artery
B. Anterior cerebral artery
C. Posterior communicating artery
D. Cavernous part of internal carotid artery (Correct Answer)

Explanation: **Explanation:** The **trigeminal (Gasserian) ganglion** is located in the Meckel’s cave (trigeminal cave) on the floor of the middle cranial fossa. Its blood supply is derived primarily from branches of the **internal carotid artery (ICA)** and the **middle meningeal artery**. 1. **Why Option D is Correct:** The **cavernous part of the ICA** gives off small ganglionic branches that directly supply the trigeminal ganglion. Additionally, the **accessory meningeal artery** and the **middle meningeal artery** (branches of the maxillary artery) provide significant contributions. 2. **Why Other Options are Incorrect:** * **Basilar Artery:** Supplies the brainstem (pons and medulla) and the cerebellum. While it gives rise to the Superior Cerebellar Artery (SCA) which may contact the trigeminal nerve root, it does not supply the ganglion itself. * **Anterior Cerebral Artery (ACA):** Supplies the medial surface of the cerebral hemispheres (frontal and parietal lobes). * **Posterior Communicating Artery:** Forms part of the Circle of Willis and connects the ICA with the Posterior Cerebral Artery; it does not extend to the floor of the middle cranial fossa to supply the ganglion. **High-Yield NEET-PG Pearls:** * **Location:** The ganglion sits in a dural recess called **Meckel’s Cave**, lateral to the cavernous sinus. * **Clinical Correlation:** Trigeminal neuralgia is often caused by vascular compression of the nerve root (most commonly by the **Superior Cerebellar Artery**), but the ganglion’s blood supply remains a distinct anatomical entity. * **Surgical Note:** During procedures on the cavernous sinus or Gasserian ganglion, surgeons must be mindful of these small ICA branches to prevent hemorrhage.

Question 158: Which of the following sites is not typically involved in a posterior cerebral artery infarct?

A. Midbrain
B. Thalamus
C. Temporal lobe
D. Anterior cerebral cortex (Correct Answer)

Explanation: The **Posterior Cerebral Artery (PCA)** is the terminal branch of the basilar artery. It primarily supplies the posterior aspects of the brain, including the brainstem, diencephalon, and the inferomedial aspects of the temporal and occipital lobes [1]. **Why the Correct Answer is Right:** * **Anterior Cerebral Cortex:** This region is supplied by the **Anterior Cerebral Artery (ACA)** (medial aspect) and the **Middle Cerebral Artery (MCA)** (lateral aspect) [1]. The PCA does not extend its supply to the frontal or anterior parietal regions; therefore, an infarct in the PCA territory will spare the anterior cortex. **Why the Other Options are Wrong:** * **Midbrain:** The PCA gives off small perforating branches (paramedian and short circumflex) that supply the midbrain. A PCA infarct can lead to **Weber’s Syndrome** (ipsilateral CN III palsy and contralateral hemiplegia). * **Thalamus:** The **Thalamoperforating** and **Thalamogeniculate** arteries are branches of the PCA [1]. Occlusion leads to Dejerine-Roussy syndrome (thalamic pain syndrome). * **Temporal Lobe:** The PCA supplies the inferior and medial surfaces of the temporal lobe (including the hippocampus). Damage here can result in memory deficits. **NEET-PG High-Yield Pearls:** 1. **Visual Field Defect:** The most common finding in a PCA infarct is **contralateral homonymous hemianopia with macular sparing** (due to collateral supply to the occipital pole from the MCA) [2]. 2. **Alexia without Agraphia:** Occurs when the dominant PCA territory (including the splenium of the corpus callosum) is involved. 3. **Cortical Blindness (Anton Syndrome):** Bilateral PCA infarction leads to blindness where the patient denies their vision loss.

Question 159: Absence of the corpus callosum leads to which of the following?

A. Hemiparesis
B. Hemisensory loss
C. Astereognosis
D. No neurological manifestations (Correct Answer)

Explanation: **Explanation:** The **corpus callosum** is the largest commissural fiber bundle connecting the two cerebral hemispheres. Interestingly, in cases of **congenital agenesis** (complete or partial absence) of the corpus callosum, patients typically present with **no overt neurological manifestations** or focal deficits [2]. This is due to **neuroplasticity** and the compensatory development of alternative pathways, such as the **Probst bundles** (longitudinal white matter tracts) and the enlargement of the anterior and posterior commissures, which maintain interhemispheric communication. **Why other options are incorrect:** * **A & B (Hemiparesis and Hemisensory loss):** These are "vertical" deficits resulting from damage to the corticospinal tracts or thalamocortical projections (e.g., internal capsule lesions). Since the corpus callosum handles "horizontal" interhemispheric transfer rather than primary motor or sensory output, its absence does not cause paralysis or loss of sensation. * **C (Astereognosis):** This refers to the inability to identify objects by touch, usually localized to the **parietal lobe** (superior parietal lobule) [1]. While callosal lesions can cause "tactile anomia" (inability to name an object held in the left hand), the basic ability to recognize the object's form remains intact. **High-Yield Facts for NEET-PG:** * **Probst Bundles:** These are the characteristic longitudinal fibers seen in imaging of callosal agenesis. * **Ventricles:** Agenesis often leads to **Colpocephaly** (disproportionate enlargement of the occipital horns of the lateral ventricles), giving a "racing car" appearance on axial imaging. * **Acquired Lesions:** Unlike congenital absence, *acute* surgical sectioning of the corpus callosum (commissurotomy) leads to **"Split-brain syndrome,"** characterized by alexia without agraphia and hemi-neglect.

Question 160: Which artery is a branch of the basilar artery?

A. Posterior inferior cerebellar artery
B. Posterior cerebral artery (Correct Answer)
C. Middle cerebral artery
D. Posterior communicating artery

Explanation: The **Basilar Artery** is formed by the union of the two vertebral arteries at the lower border of the pons. It terminates at the upper border of the pons by dividing into its two terminal branches: the **Posterior Cerebral Arteries (PCA)**. ### **Explanation of Options:** * **B. Posterior Cerebral Artery (Correct):** This is the terminal branch of the basilar artery. It supplies the visual cortex (occipital lobe) and the inferior surface of the temporal lobe. * **A. Posterior Inferior Cerebellar Artery (PICA):** This is a branch of the **Vertebral Artery**, not the basilar artery. It is the most common site for strokes leading to Lateral Medullary (Wallenberg) Syndrome. * **C. Middle Cerebral Artery (MCA):** This is the largest terminal branch of the **Internal Carotid Artery (ICA)**. It is the most common artery involved in ischemic strokes. * **D. Posterior Communicating Artery:** This is a branch of the **Internal Carotid Artery**. It connects the ICA system with the PCA (vertebrobasilar system) to complete the Circle of Willis. ### **High-Yield NEET-PG Facts:** 1. **Branches of the Basilar Artery (Mnemonic: APPS):** * **A**nterior Inferior Cerebellar Artery (AICA) * **P**ontine branches * **P**osterior Cerebral Artery (Terminal branch) * **S**uperior Cerebellar Artery 2. **Labyrinthine Artery:** Usually a branch of the AICA (from the basilar artery), it supplies the inner ear. 3. **Circle of Willis:** The basilar artery contributes to the posterior part of the circle via the PCAs. Note that the **Anterior Cerebral Artery** and **Middle Cerebral Artery** are both branches of the Internal Carotid Artery.

Practice by Chapter

Cerebral Hemispheres

Practice Questions

Diencephalon

Practice Questions

Brainstem

Practice Questions

Cerebellum

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Basal Ganglia

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Limbic System

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Ventricular System and CSF

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Blood Supply of the Brain

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Cranial Nerves and Nuclei

Practice Questions

Functional Systems and Pathways

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Applied Neuroanatomy

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Neuroimaging Correlations

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