Brain and Neuroanatomy — MCQs

Brain and Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 391: Area numbers for the somatosensory area include:

A. 5 & 7
B. 1, 2 & 3 (Correct Answer)
C. 4 & 6
D. 16 & 18

Explanation: ***1, 2 & 3*** - These Brodmann areas (1, 2, and 3) collectively represent the **primary somatosensory cortex**, located in the postcentral gyrus [1]. - This region is responsible for processing **tactile** and **proprioceptive information** from the body [1]. *5 & 7* - Brodmann areas 5 and 7 are part of the **posterior parietal cortex**, involved in **multimodal sensory association** and spatial awareness [1]. - While they process sensory information, they are considered **somatosensory association areas**, not the primary somatosensory cortex [1]. *4 & 6* - Brodmann area 4 is the **primary motor cortex**, responsible for initiating voluntary movements. - Brodmann area 6 is the **premotor and supplementary motor cortex**, involved in planning and coordinating movements [2]. *16 & 18* - Areas 16 and 18 are not associated with somatosensory function. - Brodmann area 18 is a **visual association area** (secondary visual cortex), involved in processing and interpreting visual information.

Question 392: Hemiballismus is due to lesion of

A. Putamen
B. Subthalamic nucleus (Correct Answer)
C. Caudate nucleus
D. Globus pallidus

Explanation: Subthalamic nucleus [1] - **Hemiballismus** is characterized by **unilateral, involuntary, violent, flinging movements** of the proximal musculature, primarily affecting the limbs. - This symptom complex is classically associated with a lesion in the **contralateral subthalamic nucleus (STN)**, which is part of the basal ganglia circuit [1]. *Putamen* - Lesions of the putamen are more commonly associated with other movement disorders such as **dystonia** or **parkinsonian symptoms**, not hemiballismus. - The putamen plays a key role in **motor learning and habit formation**, and its dysfunction leads to a range of motor control problems. *Caudate nucleus* - Damage to the caudate nucleus is often linked to **Huntington's disease**, which involves **chorea** (irregular, rapid, uncontrolled movements) and cognitive decline [1]. - While it is part of the basal ganglia loop, its primary role in movement control is distinct from the STN's involvement in hemiballismus. *Globus pallidus* - Lesions of the globus pallidus are associated with different movement disorders, such as **dystonia** and **bradykinesia**. [1] - The globus pallidus (particularly the internal segment) is the primary output nucleus of the basal ganglia, but its dysfunction does not typically produce hemiballismus.

Question 393: A 68-year-old man has many months history of progressive hearing loss, unsteady gait, tinnitus, and facial pain. An MRI scan reveals a tumor at the cerebellopontine angle. Which of the following cranial nerves is this tumor most likely to affect?

A. sixth cranial nerve
B. eighth cranial nerve (Correct Answer)
C. tenth cranial nerve
D. fourth cranial nerve

Explanation: ***eighth cranial nerve*** - The **eighth cranial nerve (vestibulocochlear nerve)** is located in the **cerebellopontine angle** and is responsible for **hearing and balance**. [1], [2] - Symptoms like **progressive hearing loss, tinnitus, and unsteady gait (vertigo)** are classic signs of compression or damage to this nerve, often caused by an **acoustic neuroma (vestibular schwannoma)** in this region. [2], [3] - **CN VIII is the FIRST and MOST COMMONLY affected nerve** in cerebellopontine angle tumors, making it the correct answer. - The **facial pain** mentioned suggests compression of the **trigeminal nerve (CN V)** by a large tumor, which can occur as the tumor expands, but CN VIII remains the primary nerve affected. *sixth cranial nerve* - The **sixth cranial nerve (abducens nerve)** innervates the **lateral rectus muscle**, responsible for **abduction of the eye**. - Damage would typically result in **diplopia** and an inability to move the eye laterally, which is not described. - This nerve is **rarely affected** by CPA tumors due to its anatomical location. *tenth cranial nerve* - The **tenth cranial nerve (vagus nerve)** controls **pharyngeal and laryngeal muscles**, as well as **parasympathetic innervation to many organs**. - Damage would typically cause **dysphagia**, **hoarseness**, or autonomic dysfunction, none of which are presented. - The vagus nerve is **not typically affected** by CPA tumors. *fourth cranial nerve* - The **fourth cranial nerve (trochlear nerve)** innervates the **superior oblique muscle**, aiding in **eye movement**. - Damage would primarily lead to **vertical diplopia**, particularly when looking down and in, which is not mentioned as a symptom. - This nerve is **not affected** by CPA tumors due to its location.

Question 394: Most common route for transmission of meningitis from CNS to inner ear is -

A. Endolymphatic sac
B. Cochlear Aqueduct (Correct Answer)
C. Vestibular Aqueduct
D. Hyrtl's fissure

Explanation: Cochlear Aqueduct - The cochlear aqueduct is a narrow bony canal that connects the subarachnoid space (containing cerebrospinal fluid) directly to the perilymphatic space of the cochlea, making it a direct route for pathogen spread. - This anatomical connection allows bacteria or inflammatory agents from meningitis to easily access the inner ear, leading to sensorineural hearing loss [1]. *Endolymphatic sac* - The endolymphatic sac is involved in the fluid balance of the inner ear but is not a primary or direct conduit between the CNS and the inner ear chambers. - While infections can spread, it's not the most direct or common initial pathway for meningitis pathogens. *Vestibular Aqueduct* - The vestibular aqueduct houses the endolymphatic duct and sac, but it does not directly connect the subarachnoid space to the perilymphatic space like the cochlear aqueduct. - Its role is mainly in the fluid dynamics of the endolymphatic system, distinct from the perilymphatic communication with the CNS. *Hyrtl's fissure* - Hyrtl's fissure (or tympanomeningeal fissure) is a potential pathway connecting the posterior cranial fossa to the middle ear, not directly the inner ear from the CNS. - While it can be a route for infection into the middle ear, it is a less direct or frequent route for meningitis pathogens to reach the inner ear compared to the cochlear aqueduct.

Question 395: Blood supply to spinal nerve roots is derived from?

A. Posterior spinal artery
B. Anterior spinal artery
C. Ascending cervical artery
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - The **spinal nerve roots** receive their blood supply from a **complex vascular network** involving multiple arterial sources. - All three arteries listed contribute to the perfusion of nerve roots at different levels of the spinal cord. **Each contributing artery:** ***Anterior spinal artery*** - Forms from the union of branches from the **vertebral arteries** - Supplies the **anterior two-thirds** of the spinal cord and gives off branches to the **ventral (anterior) nerve roots** - Provides the primary blood supply to motor nerve roots ***Posterior spinal arteries*** - Typically arise from the **vertebral arteries** or **PICA** (posterior inferior cerebellar artery) - Supply the **posterior one-third** of the spinal cord and contribute to the **dorsal (posterior) nerve roots** - Provide vascular support to sensory nerve roots ***Ascending cervical artery*** - Branch of the **inferior thyroid artery** (from the thyrocervical trunk of the subclavian artery) - Provides **segmental radicular branches** that reinforce the blood supply to the **cervical spinal cord and nerve roots** - Part of the extensive collateral circulation supporting the spinal vasculature **Key concept:** The spinal nerve roots are supplied by a **redundant vascular network** to ensure continuous perfusion, involving longitudinal vessels (ASA, PSA) and segmental feeders (radicular arteries including ascending cervical).

Question 396: A child presented with weakness of limbs, cannot sit properly and swaying both sides while walking. The lesion is in

A. Neocerebellum
B. Cerebellopontine area
C. Cerebellar vermis (Correct Answer)
D. Cerebellar hemisphere

Explanation: ***Cerebellar vermis*** - Lesions in the **cerebellar vermis** typically cause **truncal ataxia**, leading to difficulty sitting upright and a wide-based gait with swaying [1]. - The vermis is responsible for coordinating **proximal and trunk movements**, which are essential for maintaining balance and posture. *Neocerebellum* - The neocerebellum (lateral hemispheres) is primarily involved in **fine motor coordination** and planning of voluntary movements [1]. - Lesions here typically result in **appendicular ataxia**, affecting movements of the limbs (e.g., dysmetria, dysdiadochokinesia), rather than truncal instability [1]. *Cerebellopontine area* - The cerebellopontine angle (CPA) is a region at the base of the brain where the cerebellum, pons, and medulla meet. - Lesions in this area often present with **cranial nerve palsies** (especially CNs VII and VIII), along with ataxia, but not specifically isolated truncal ataxia. *Cerebellar hemisphere* - Similar to the neocerebellum, the cerebellar hemispheres are primarily involved in **coordinating limb movements**. - Lesions here would typically cause **ipsilateral appendicular ataxia**, affecting the limbs on the same side as the lesion, rather than severe truncal instability [1].

Question 397: Acoustic neuroma commonly arises from which of the following nerves?

A. IXth nerve
B. Cochlear nerve
C. Inferior division of vestibular nerve (Correct Answer)
D. Superior division of vestibular nerve

Explanation: ***Inferior division of vestibular nerve*** - Acoustic neuromas, also known as **vestibular schwannomas**, originate from the **Schwann cells** lining the vestibular portion of the **eighth cranial nerve (CN VIII)** [1]. - Approximately **60-70%** of acoustic neuromas arise from the **inferior division of the vestibular nerve**, making it the most common site of origin. - The inferior vestibular nerve innervates the saccule and posterior semicircular canal. *Superior division of vestibular nerve* - While acoustic neuromas can arise from the **superior division of the vestibular nerve**, this is **less common** than the inferior division. - The superior division innervates the utricle and anterior/lateral semicircular canals. - When tumors do arise here, they present with similar symptoms of hearing loss and balance disturbance. *Cochlear nerve* - The **cochlear nerve** is responsible for transmitting auditory information to the brain. - Although it is part of the **vestibulocochlear nerve (CN VIII)**, acoustic neuromas rarely arise primarily from the cochlear portion. - However, auditory symptoms (hearing loss, tinnitus) commonly occur due to tumor compression of the cochlear nerve. *IXth nerve* - The **IXth cranial nerve** is the **glossopharyngeal nerve**, which is involved in taste, swallowing, and sensation from the pharynx. - Tumors of the glossopharyngeal nerve are extremely rare and are not classified as acoustic neuromas. - Acoustic neuromas are specific to the vestibulocochlear nerve (CN VIII).

Question 398: Auditory pathway passes through -

A. Fornix
B. Lateral geniculate body
C. Medial geniculate body (Correct Answer)
D. Reticular formation

Explanation: ***Medial geniculate body*** - The **medial geniculate body (MGB)** is the **thalamic relay nucleus** for the **auditory pathway** [1] - It receives input from the **inferior colliculus** and projects to the **primary auditory cortex** (Heschl's gyrus) in the temporal lobe [1], [3] - Essential for processing and relaying auditory information from the brainstem to the cortex *Fornix* - The **fornix** is a C-shaped white matter tract that is part of the **limbic system**, connecting the hippocampus to the mammillary bodies and septal nuclei [2] - It is primarily involved in **memory consolidation** and emotional processing, not auditory function - Not a component of the auditory pathway *Lateral geniculate body* - The **lateral geniculate body (LGB)** is the **thalamic relay nucleus** for the **visual pathway** - It receives input from the retina via the optic tract and projects to the primary visual cortex - Dedicated exclusively to visual processing, not auditory information *Reticular formation* - The **reticular formation** is a diffuse network of neurons in the brainstem involved in **arousal, consciousness, sleep-wake cycles**, and autonomic regulation [2] - While it can modulate attention to auditory stimuli through ascending reticular activating system (ARAS), it is not part of the **primary ascending auditory pathway** - The dedicated auditory pathway goes: cochlear nuclei → superior olivary complex → lateral lemniscus → inferior colliculus → medial geniculate body → auditory cortex [1], [3]

Question 399: Dysmetria is due to lesion of ______________

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

Explanation: Cerebellum * **Dysmetria** is a cardinal sign of **cerebellar dysfunction**, specifically referring to the inability to accurately move an intended distance [1]. * The cerebellum is crucial for coordinating voluntary movements, balance, and motor learning, and lesions here impair the **accuracy and smoothness of movement** [1], [2]. Pons * The **pons** primarily serves as a relay station between the cerebrum and cerebellum, and contains nuclei for cranial nerves (V, VI, VII, VIII) [3]. * Lesions in the pons typically cause symptoms like **paralysis**, sensory deficits, and problems with eye movements, rather than dysmetria [3]. Midbrain * The **midbrain** is involved in motor control, visual and auditory processing, and sleep-wake cycles [3]. * Lesions here can cause **oculomotor deficits**, parkinsonian symptoms, or consciousness disturbances, but dysmetria is not a primary symptom [3]. Medulla * The **medulla oblongata** controls vital autonomic functions such as breathing, heart rate, and blood pressure. * Damage to the medulla is often life-threatening and can cause respiratory failure or swallowing difficulties, but **dysmetria is not a direct result of medullary lesions**.

Question 400: Wallenberg syndrome involves which artery?

A. Subclavian artery
B. Posterior cerebral artery
C. Posterior inferior cerebellar artery (Correct Answer)
D. Anterior inferior cerebellar artery

Explanation: ***Posterior inferior cerebellar artery*** - **Wallenberg syndrome**, also known as **lateral medullary syndrome**, is most commonly caused by an infarction in the territory supplied by the **posterior inferior cerebellar artery (PICA)**. - The PICA supplies the **lateral medulla**, which contains several crucial nuclei and tracts, including the nucleus ambiguus, trigeminal nucleus, vestibular nuclei, and spinothalamic tract, leading to the characteristic clinical presentation of Wallenberg syndrome. *Subclavian artery* - The **subclavian artery** is a large artery in the upper thorax that supplies blood to the upper limbs, head, and neck. - While it can be involved in conditions like **subclavian steal syndrome**, it does not directly supply the lateral medulla responsible for Wallenberg syndrome. *Posterior cerebral artery* - The **posterior cerebral artery** primarily supplies the occipital lobe, temporal lobe, and parts of the thalamus and midbrain. - Infarction in the PCA territory typically leads to symptoms like **hemianopia**, visual field defects, and memory deficits, not the constellation of symptoms seen in Wallenberg syndrome. *Anterior inferior cerebellar artery* - The **anterior inferior cerebellar artery (AICA)** supplies the anterior and lateral parts of the cerebellum and the pontomedullary junction, leading to **lateral pontine syndrome** when infarcted. - Symptoms of AICA infarction include ipsilateral facial paralysis, hearing loss, and cerebellar ataxia, which are distinct from Wallenberg syndrome.

Practice by Chapter

Cerebral Hemispheres

Practice Questions

Diencephalon

Practice Questions

Brainstem

Practice Questions

Cerebellum

Practice Questions

Basal Ganglia

Practice Questions

Limbic System

Practice Questions

Ventricular System and CSF

Practice Questions

Blood Supply of the Brain

Practice Questions

Cranial Nerves and Nuclei

Practice Questions

Functional Systems and Pathways

Practice Questions

Applied Neuroanatomy

Practice Questions

Neuroimaging Correlations

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free