Neuroanatomy Practice Questions

Q: Which of the following is the largest branch of the vertebral artery?

Posterior inferior cerebellar artery. **Explanation:** The **Posterior Inferior Cerebellar Artery (PICA)** is the largest and most significant branch of the fourth (V4) segment of the vertebral artery. It typically arises near the lower end of the medulla oblongata and follows a tortuous course around the medulla to supply the postero-inferior surface of the cerebellum and the choroid plexus of the fourth ventricle. **Analysis of Options:** * **Option A (Correct):** PICA is the largest branch. It is clinically vital as it supplies the lateral part of the medulla; its occlusion leads to Lateral Medullary Syndrome (Wallenberg Syndrome). * **Option B (Incorrect):** The **Anterior Spinal Artery** is formed by the union of two small branches from the vertebral arteries. While it is long and supplies the anterior two-thirds of the spinal cord, it is smaller in caliber than the PICA. * **Option C (Incorrect):** **Meningeal branches** are small vessels that supply the bone and dura mater of the posterior cranial fossa. They are significantly smaller than the major cerebellar branches. **High-Yield Facts for NEET-PG:** 1. **Origin:** The vertebral artery is the first branch of the first part of the subclavian artery. 2. **Course:** It enters the transverse foramen of the **C6 vertebra** (not C7). 3. **Basilar Artery:** The two vertebral arteries join at the lower border of the pons to form the basilar artery. 4. **Clinical Correlation:** **Wallenberg Syndrome** (PICA occlusion) presents with "crossed anesthesia" (ipsilateral loss of pain/temp on the face and contralateral loss on the body), dysphagia, and ataxia.

Q: To which of the following thalamic nuclei do the cerebellar fibers project?

Ventral lateral nucleus. ### Explanation The thalamus acts as the primary relay station for sensory and motor pathways [1]. The **Ventral Lateral (VL) nucleus** is the specific motor relay nucleus that receives input from the **cerebellum** (specifically the dentate nucleus via the dentatothalamic tract) and the basal ganglia [2]. It then projects these signals to the primary motor cortex (Brodmann area 4) and premotor cortex, playing a crucial role in the coordination and planning of movement [2]. **Analysis of Options:** * **Ventral Lateral (VL) Nucleus (Correct):** Receives input from the contralateral cerebellum and projects to the motor cortex. It is essential for motor control. * **Anterior Nucleus:** Part of the **Limbic System**. It receives input from the mammillary bodies (via the mammillothalamic tract) and projects to the cingulate gyrus. It is involved in memory and emotion. * **Lateral Dorsal (LD) Nucleus:** Also part of the limbic system; it functions similarly to the anterior nucleus and projects to the cingulate gyrus. * **Lateral Posterior (LP) Nucleus:** Acts as an integration nucleus for sensory information, having strong connections with the sensory association areas of the parietal lobe. **High-Yield Facts for NEET-PG:** 1. **Ventral Posterolateral (VPL) Nucleus:** Relays sensory information from the body (DCML and Spinothalamic tracts). 2. **Ventral Posteromedial (VPM) Nucleus:** Relays sensory information from the face (Trigeminal pathway) and taste (Solitariothalamic tract). Remember: **M** for **M**outh/Face. 3. **Medial Geniculate Body (MGB):** Relay for **Hearing** (M for Music) [3]. 4. **Lateral Geniculate Body (LGB):** Relay for **Vision** (L for Light). 5. **Lesion of VL/Cerebellar pathways:** Results in intention tremors and ataxia.

Q: Bitemporal hemianopia is seen in which of the following lesions?

Optic chiasmal lesion. **Explanation:** **1. Why Optic Chiasmal Lesion is Correct:** Bitemporal hemianopia is the classic visual field defect resulting from a lesion at the **optic chiasm**, most commonly due to a pituitary adenoma or craniopharyngioma [2]. At the chiasm, the nerve fibers from the **nasal retina** of both eyes decussate (cross over) [1]. Since the nasal retina is responsible for perceiving the **temporal (peripheral) visual fields**, a midline compression of these crossing fibers leads to the loss of the outer half of the vision in both eyes [2]. **2. Why the Other Options are Incorrect:** * **Optic Nerve Lesion:** Damage here occurs distal to the chiasm and results in **ipsilateral monocular blindness** (total vision loss in one eye) [2]. * **Optic Tract Lesion:** This involves fibers from the ipsilateral temporal retina and contralateral nasal retina [1]. Lesions here result in **contralateral homonymous hemianopia** (loss of the same side of the visual field in both eyes) [2]. * **Optic Radiation Lesion:** Depending on the location, these cause contralateral homonymous hemianopia. Specifically, a temporal lobe lesion (Meyer’s loop) causes "pie in the sky" (superior quadrantanopia), while a parietal lobe lesion causes "pie on the floor" (inferior quadrantanopia). **3. NEET-PG High-Yield Clinical Pearls:** * **Pituitary Adenoma:** Compresses the chiasm from **below**, often affecting the superior temporal quadrants first [3]. * **Craniopharyngioma:** Compresses the chiasm from **above**, often affecting the inferior temporal quadrants first. * **Meyer’s Loop:** Fibers pass through the temporal lobe; damage leads to Contralateral Superior Quadrantanopia. * **Macular Sparing:** Characteristically seen in posterior cerebral artery (PCA) strokes affecting the primary visual cortex (Area 17) due to collateral supply from the middle cerebral artery (MCA) [2].

Q: A patient is brought to the emergency department following a road traffic accident. MRI shows injury to the corpus striatum. This patient is MOST likely to suffer from which of the following movement disorders?

Chorea. The **corpus striatum** (composed of the caudate nucleus and the putamen) is a key component of the basal ganglia circuitry. It serves as the primary input station, receiving excitatory signals from the cortex and projecting inhibitory signals to the globus pallidus [2]. **Why Chorea is the Correct Answer:** Injury to the corpus striatum, particularly the **caudate nucleus**, leads to the loss of GABAergic inhibitory neurons [3]. This results in the disinhibition of the thalamus, causing involuntary, jerky, "dance-like" movements known as **Chorea**. This is classically seen in Huntington’s disease, where atrophy of the caudate nucleus is the hallmark [1]. **Analysis of Incorrect Options:** * **Parkinsonism:** This is primarily caused by the degeneration of dopaminergic neurons in the **Substantia Nigra pars compacta (SNpc)**, leading to a deficiency of dopamine in the striatum [3]. * **Hemiballismus:** This characterized by violent, flinging movements of the limbs and is specifically associated with a lesion in the **Subthalamic Nucleus (STN)**. * **Athetosis:** This involves slow, writhing, "snake-like" movements, typically resulting from lesions in the **Globus Pallidus**. **High-Yield Clinical Pearls for NEET-PG:** * **Corpus Striatum** = Caudate Nucleus + Lentiform Nucleus (Putamen + Globus Pallidus). * **Neostriatum (Striatum)** = Caudate + Putamen. * **Lentiform Nucleus** = Putamen + Globus Pallidus. * **Wilson’s Disease:** Characterized by cavitation and degeneration of the **Putamen**. * **Huntington’s Disease:** Characterized by **Caudate** atrophy and **Chorea** [3].

Q: In lateral medullary syndrome (Wallenberg), where is the lesion located?

Spinal tract of the trigeminal nerve. **Explanation:** **Lateral Medullary Syndrome (Wallenberg Syndrome)** occurs due to an infarct in the territory of the **Posterior Inferior Cerebellar Artery (PICA)** or the vertebral artery. It involves the dorsolateral portion of the medulla. 1. **Why Option B is correct:** The **Spinal tract and nucleus of the Trigeminal nerve** are located in the lateral medulla. Damage to these structures results in the classic clinical finding of **ipsilateral loss of pain and temperature sensation over the face**. This is a hallmark of the syndrome, alongside contralateral loss of pain/temperature in the body (due to lateral spinothalamic tract involvement). 2. **Why incorrect options are wrong:** * **A. Trigeminal motor nucleus:** This nucleus is located in the **Pons**, not the medulla. Its involvement would affect the muscles of mastication. * **C. Medial lemniscus:** This structure is located **medially** in the medulla. Its involvement occurs in **Medial Medullary Syndrome (Dejerine Syndrome)**, leading to loss of vibration and proprioception. * **D. Pyramidal tract:** Also located **medially** (forming the pyramids), its involvement in Medial Medullary Syndrome causes contralateral hemiplegia. Lateral medullary syndrome characteristically **spares** motor function. **High-Yield Clinical Pearls for NEET-PG:** * **Nucleus Ambiguus involvement:** Leads to dysphagia, dysarthria, and loss of gag reflex (CN IX, X). * **Vestibular Nuclei involvement:** Causes vertigo, nystagmus, and nausea. * **Sympathetic tract involvement:** Leads to **ipsilateral Horner’s syndrome** (miosis, ptosis, anhidrosis). * **Inferior Cerebellar Peduncle:** Causes ipsilateral ataxia. * **Rule of 4s:** Remember that "Lateral" syndromes (Wallenberg) involve cranial nerve nuclei that do not divide evenly into 12 (V, VII, IX, X, XI), whereas "Medial" syndromes involve those that do (III, IV, VI, XII).

Q: All of the following are components of Horner's syndrome except?

Exophthalmos. Explanation: Horner’s syndrome is caused by a lesion in the **oculosympathetic pathway** (a three-neuron chain). The sympathetic nervous system is responsible for pupillary dilation, eyelid elevation (via the superior tarsal muscle), and facial sweating. **Why Exophthalmos is the correct answer:** In Horner’s syndrome, the patient actually presents with **Enophthalmos** (the appearance of a sunken eye), not exophthalmos (protruding eye). This is a "pseudo-enophthalmos" caused by the narrowing of the palpebral fissure due to eyelid drooping. Exophthalmos is typically associated with conditions like Graves' ophthalmopathy, not sympathetic paralysis. **Analysis of incorrect options:** * **Ptosis:** Occurs due to paralysis of **Müller’s muscle** (superior tarsal muscle). It is a "partial ptosis" compared to the complete ptosis seen in 3rd nerve palsy. * **Anhidrosis:** Loss of sympathetic supply to the sweat glands of the face leads to a lack of sweating on the affected side. * **Loss of ciliospinal reflex:** This reflex involves pupillary dilation in response to pain applied to the neck skin. Since the sympathetic pathway is disrupted, this reflex is characteristically absent. **NEET-PG High-Yield Pearls:** * **The Classic Triad:** Ptosis, Miosis (constricted pupil), and Anhidrosis. * **Pancoast Tumor:** A common cause of Horner’s syndrome due to compression of the stellate ganglion by an apical lung tumor. * **Pharmacological Testing:** Cocaine eye drops fail to dilate a Horner’s pupil, confirming the diagnosis. * **Heterochromia Iridum:** If Horner’s is congenital, the affected eye may have a lighter-colored iris due to the role of sympathetics in melanin deposition.

Q: Which nucleus is primarily involved in Alzheimer's disease?

Basal nucleus of Meynert. **Explanation:** **1. Why the Basal Nucleus of Meynert is correct:** The **Basal Nucleus of Meynert (BNM)**, located in the substantia innominata of the basal forebrain, is the primary source of **cholinergic (Acetylcholine)** innervation to the entire cerebral cortex and amygdala. In **Alzheimer’s Disease**, there is a profound and selective degeneration of these cholinergic neurons. This loss leads to a significant deficit in acetylcholine levels, which is directly correlated with the cognitive decline and memory impairment seen in patients [1]. Most current pharmacological treatments (Cholinesterase inhibitors like Donepezil) aim to compensate for this loss [2]. **2. Why the other options are incorrect:** * **Raphe Nucleus:** These nuclei are located in the brainstem and are the primary source of **Serotonin**. While serotonin levels may fluctuate in various dementias, it is not the primary site of pathology in Alzheimer's. * **Superior Salivary Nucleus:** This is a parasympathetic nucleus of the **Facial Nerve (CN VII)** located in the pons. It controls lacrimation and salivation (submandibular/sublingual glands) and has no role in cognitive function. * **Basal Lobe of Cerebellum:** This is an anatomical misnomer; the cerebellum consists of anterior, posterior, and flocculonodular lobes. The cerebellum is primarily involved in motor coordination, not the pathogenesis of Alzheimer's. **3. Clinical Pearls for NEET-PG:** * **Neurotransmitter involved:** Acetylcholine (ACh). * **Histopathological Hallmarks:** Amyloid plaques (extracellular) and Neurofibrillary tangles (intracellular Tau protein) [1]. * **Hirano Bodies:** Eosinophilic, rod-like inclusions often found in the hippocampus of Alzheimer’s patients. * **Imaging:** MRI typically shows **Hippocampal atrophy** and compensatory ventricular enlargement (hydrocephalus ex-vacuo).

Q: True regarding the lateral spinothalamic tract is:

Lower most fibers are lateral. The **Lateral Spinothalamic Tract (LSTT)** is the primary pathway for transmitting pain and temperature sensations. ### **Why Option D is Correct** The LSTT exhibits specific **somatotopic organization** (lamination). As the tract ascends the spinal cord, new fibers from higher segments are added to the **medial** aspect. Consequently: * **Sacral and Lumbar fibers** (lower body) are pushed to the **lateral** periphery. * **Cervical fibers** (upper body) are located most **medially**. This "Sacral-out, Cervical-in" arrangement is crucial for understanding clinical syndromes like syringomyelia. ### **Analysis of Incorrect Options** * **A. Transmits contralateral touch:** Incorrect. The LSTT transmits pain and temperature. Crude touch is carried by the **Anterior Spinothalamic Tract**, while fine touch is carried by the **Dorsal Columns**. * **B. Transmits ipsilateral pain:** Incorrect. The LSTT transmits **contralateral** sensations. Second-order neurons decussate (cross) almost immediately at the level of the spinal cord. * **C. Crosses at the thalamus:** Incorrect. The fibers cross in the **spinal cord** (via the anterior white commissure), usually within 1-2 segments of entry. The thalamus (VPL nucleus) is where the second-order neurons synapse with third-order neurons. ### **High-Yield Clinical Pearls** * **Brown-Séquard Syndrome:** Hemisection of the cord results in **contralateral** loss of pain and temperature (LSTT) 1-2 segments below the lesion. * **Intramedullary Tumors:** These expand from the center of the cord, affecting medial (cervical) fibers first, leading to "sacral sparing." * **Syringomyelia:** Classically causes a "cape-like" distribution of sensory loss because it damages the decussating fibers in the anterior white commissure.

Q: Which of the following is NOT an association fiber?

Corona radiata. To master neuroanatomy for NEET-PG, it is essential to classify white matter fibers into three types: **Association**, **Commissural**, and **Projection** fibers. ### **Explanation of the Correct Answer** **A. Corona radiata** is the correct answer because it consists of **Projection fibers**. These fibers connect the cerebral cortex with lower centers such as the thalamus, brainstem, or spinal cord [2]. They travel vertically, passing through the internal capsule [1], [3]. Since they connect different levels of the central nervous system (superior to inferior) rather than areas within the same hemisphere, they are not association fibers. ### **Analysis of Incorrect Options** Association fibers connect different cortical areas within the **same cerebral hemisphere**. * **B. Arcuate fasciculus:** A long association fiber connecting the frontal lobe (Broca’s area) with the temporal lobe (Wernicke’s area). * **C. Cingulum:** A curved bundle of association fibers located within the cingulate gyrus, connecting the frontal and parietal lobes to the parahippocampal gyrus. * **D. Uncinate fasciculus:** A hook-shaped association fiber connecting the orbitofrontal cortex to the anterior temporal lobe. ### **High-Yield Clinical Pearls for NEET-PG** * **Short Association Fibers:** Also called "U-fibers," they connect adjacent gyri. * **Long Association Fibers:** Include the Superior/Inferior Longitudinal Fasciculi, Cingulum, and Uncinate Fasciculus. * **Clinical Correlation:** Damage to the **Arcuate Fasciculus** leads to **Conduction Aphasia**, characterized by poor repetition but intact comprehension and fluent speech. * **Commissural Fibers:** Connect corresponding areas of the two hemispheres (e.g., Corpus Callosum, Anterior Commissure, Hippocampal Commissure).

Q: What is true about the medial lemniscus?

It is a continuation of the dorsal column.. The **Medial Lemniscus** is a key component of the **Dorsal Column-Medial Lemniscus (DCML) pathway**, which is responsible for conveying fine touch, vibration, and conscious proprioception [1]. ### Why Option B is Correct The DCML pathway begins with first-order neurons in the dorsal root ganglia, which ascend ipsilaterally in the spinal cord as the **Gracile and Cuneate fasciculi**. These synapse in the medulla at the **Nucleus Gracilis and Nucleus Cuneatus** [1]. The second-order neurons then emerge as **internal arcuate fibers**, which decussate (cross over) in the lower medulla. After crossing, these fibers ascend through the brainstem as the **Medial Lemniscus** to reach the Thalamus (VPL nucleus) [1]. Thus, the medial lemniscus is the direct rostral continuation of the dorsal column system after decussation. ### Why Other Options are Incorrect * **Option A:** Pain and temperature sensations are carried by the **Lateral Spinothalamic Tract**, not the medial lemniscus [1], [2]. * **Option C:** The fibers of the DCML pathway cross in the **Medulla** (Sensory Decussation), not the spinal cord [1]. In contrast, the spinothalamic tract crosses at the level of the spinal cord [2]. ### NEET-PG High-Yield Pearls * **Somatotopy:** In the Medulla, the medial lemniscus is oriented "standing up" (feet anterior/ventral). In the Pons and Midbrain, it rotates and "lies down" (feet lateral) [1]. * **Blood Supply:** The medial lemniscus in the medulla is supplied by the **Anterior Spinal Artery**. Occlusion leads to **Medial Medullary Syndrome**, characterized by contralateral loss of vibration and position sense. * **Termination:** All fibers of the medial lemniscus terminate in the **Ventral Posterolateral (VPL) nucleus** of the Thalamus [1].

Question 1

Which of the following is the largest branch of the vertebral artery?

Accepted Answer

Posterior inferior cerebellar artery

Answer

Anterior spinal artery

Answer

Meningeal branches

Answer

None of the above

Question 2

To which of the following thalamic nuclei do the cerebellar fibers project?

Accepted Answer

Ventral lateral nucleus

Answer

Anterior nucleus

Answer

Lateral dorsal nucleus

Answer

Lateral posterior nucleus

Question 3

Bitemporal hemianopia is seen in which of the following lesions?

Accepted Answer

Optic chiasmal lesion

Answer

Optic nerve lesion

Answer

Optic tract lesion

Answer

Optic radiation lesion

Question 4

A patient is brought to the emergency department following a road traffic accident. MRI shows injury to the corpus striatum. This patient is MOST likely to suffer from which of the following movement disorders?

Accepted Answer

Chorea

Answer

Parkinsonism

Answer

Hemiballismus

Answer

Athetosis

Question 5

In lateral medullary syndrome (Wallenberg), where is the lesion located?

Accepted Answer

Spinal tract of the trigeminal nerve

Answer

Trigeminal motor nucleus

Answer

Medial lemniscus

Answer

Pyramidal tract

Question 6

All of the following are components of Horner's syndrome except?

Accepted Answer

Exophthalmos

Answer

Ptosis

Answer

Anhidrosis

Answer

Loss of ciliospinal reflex

Question 7

Which nucleus is primarily involved in Alzheimer's disease?

Accepted Answer

Basal nucleus of Meynert

Answer

Raphe nucleus

Answer

Superior salivary nucleus

Answer

Basal lobe of cerebellum

Question 8

True regarding the lateral spinothalamic tract is:

Accepted Answer

Lower most fibers are lateral

Answer

Transmits contralateral touch

Answer

Transmits ipsilateral pain

Answer

Crosses at the thalamus

Question 9

Which of the following is NOT an association fiber?

Accepted Answer

Corona radiata

Answer

Arcuate fasciculus

Answer

Cingulum

Answer

Uncinate fasciculus

Question 10

What is true about the medial lemniscus?

Accepted Answer

It is a continuation of the dorsal column.

Answer

It carries pain and temperature sensations.

Answer

It crosses to the opposite side in the spinal cord.

Answer

All of the above.

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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