Brain and Neuroanatomy — MCQs

Brain and Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 371: Occlusion of blood supply of the area marked in red will lead to all of the following except:

A. Urinary incontinence
B. Rectal incontinence
C. Apraxia (Constructional) (Correct Answer)
D. Peri-anal anaesthesia

Explanation: ***Apraxia (Constructional)*** - The area marked in red represents the **medial portion of the precentral gyrus (motor cortex)** and **postcentral gyrus (sensory cortex)**, as well as the **paracentral lobule**, which are supplied by the **anterior cerebral artery (ACA)**. - Constructional apraxia is typically associated with **posterior parietal lobe lesions**, particularly in the non-dominant hemisphere, which is supplied by the posterior cerebral artery and middle cerebral artery branches, not the ACA. *Urinary incontinence* - The **paracentral lobule**, located in the area supplied by the ACA (marked in red), contains centers for **bladder control** and voluntary micturition. - Damage to this region can lead to **urinary incontinence** due to disrupted cortical control over bladder function. *Rectal incontinence* - Similar to bladder control, the **paracentral lobule** also plays a role in **voluntary bowel control**. - Ischemia in this region due to ACA occlusion can therefore result in **rectal incontinence**. *Peri-anal anaesthesia* - The **somatosensory cortex** representing the lower limbs and perineum is located in the **paracentral lobule** (postcentral gyrus part). - Occlusion of the ACA, supplying this region, can lead to **sensory deficits**, including **anaesthesia** in the peri-anal area.

Question 372: What is the name of the marked blood vessel in the Circle of Willis?

A. Middle cerebral artery
B. Posterior communicating artery (Correct Answer)
C. Internal carotid artery
D. Posterior cerebral artery

Explanation: ***Posterior communicating artery*** - The image displays the Circle of Willis, and the vessel marked with 'X' is connecting the **internal carotid artery** (which branches into the middle and anterior cerebral arteries) to the **posterior cerebral artery**. - This connecting artery is the **posterior communicating artery**, an essential component of the Circle of Willis, ensuring collateral blood flow to the brain. *Middle cerebral artery* - The **middle cerebral artery** branches off the internal carotid artery and typically extends laterally into the Sylvian fissure, supplying a large part of the lateral cerebral cortex. - The marked vessel is clearly connecting proximal arteries within the Circle of Willis, not extending into the cerebral cortex peripherally. *Internal carotid artery* - The **internal carotid artery** enters the skull and gives rise to several branches, including the middle cerebral artery and the posterior communicating artery. - While it's part of the supply to the Circle of Willis, the 'X' points specifically to the **communicating segment** connecting the anterior and posterior circulations, not the main trunk of the internal carotid. *Posterior cerebral artery* - The **posterior cerebral artery** is formed by the bifurcation of the basilar artery and supplies the occipital lobe and parts of the temporal lobe. - The marked vessel is connecting to the posterior cerebral artery, but it is not the posterior cerebral artery itself; rather, it is the vessel **communicating** with it from the anterior circulation.

Question 373: What is the name of the marked blood vessel shown in brain circulation?

A. Middle cerebral artery
B. Posterior communicating artery (Correct Answer)
C. Internal carotid artery
D. Anterior communicating artery

Explanation: ***Posterior communicating artery*** - The arrow points to a vessel connecting the **anterior circulation** (internal carotid artery system) with the **posterior circulation** (vertebrobasilar system) within the **Circle of Willis**. - This specific location and function are characteristic of the **posterior communicating artery**, which typically arises from the internal carotid and joins the posterior cerebral artery. *Middle cerebral artery* - The middle cerebral artery is a large artery that branches off the **internal carotid artery** and typically extends laterally and superiorly to supply a large part of the **cerebral hemispheres**. - It would appear more prominent and more laterally positioned, not forming a direct "communicating" link in the central Circle of Willis as shown. *Internal carotid artery* - The internal carotid artery ascends from the neck into the skull and bifurcates into the **anterior and middle cerebral arteries**. - While visible in the image, the arrow is pointing to a smaller anastomotic branch, not the main trunk of the internal carotid artery. *Anterior communicating artery* - The **anterior communicating artery** connects the two **anterior cerebral arteries** at the anterior aspect of the Circle of Willis. - This is a distinct location from that indicated by the arrow, which shows a vessel connecting anterior to posterior circulation, not linking the two anterior cerebral arteries.

Question 374: Which one of the following is the myelinating cell of Central Nervous System?

A. Astrocyte
B. Oligodendrocyte (Correct Answer)
C. Microglia
D. Schwann cell

Explanation: ***Oligodendrocyte*** - **Oligodendrocytes** are the primary cells responsible for producing and maintaining the **myelin sheath** around axons in the **Central Nervous System (CNS)** [2], [3]. - Each oligodendrocyte can myelinate multiple axons or multiple segments of the same axon [3]. *Astrocyte* - **Astrocytes** are star-shaped glial cells that provide structural and metabolic support to neurons in the CNS [1]. - They are involved in forming the **blood-brain barrier** and regulating the chemical environment around neurons, but they do not produce myelin. *Microglia* - **Microglia** are the resident **immune cells** of the CNS, functioning as macrophages [1]. - They are primarily involved in immune surveillance, phagocytosis of cellular debris and pathogens, and inflammatory responses, not myelination [1]. *Schwann cell* - **Schwann cells** are the myelinating cells of the **Peripheral Nervous System (PNS)** [2], [3]. - Unlike oligodendrocytes, each Schwann cell typically myelinates only a single axon segment [3].

Question 375: The glymphatic system is the lymphatic-like structure of which system?

A. Central Nervous System (Correct Answer)
B. Gastrointestinal
C. Respiratory
D. Renal

Explanation: ***Central Nervous System*** - The **glymphatic system** is a specialized waste clearance pathway unique to the **central nervous system (CNS)**. - It facilitates the removal of metabolic waste products, including **amyloid-beta**, from the brain, playing a crucial role in CNS health. *Gastro-intestinal* - The gastrointestinal system has its own extensive lymphatic network, including **Peyer's patches** and **mesenteric lymph nodes**, for immune surveillance and lipid absorption. - These structures differ significantly in function and anatomy from the brain's glymphatic system. *Respiratory* - The respiratory system is equipped with **bronchial lymphatics** and **pulmonary lymph nodes** that drain fluid and immune cells from the lungs. - This system is involved in immune responses and fluid balance in the lungs, not directly related to brain waste clearance. *Renal* - The renal system has lymphatic drainage associated with the kidneys, which helps in the return of interstitial fluid and immune cells [1]. - This system is distinct from the glymphatic system and primarily involved in kidney function and fluid balance [1].

Question 376: Contralateral Homonymous upper quadrantanopia is the type of visual loss seen when the lesion is located at which one of the following anatomical locations?

A. Temporal lobe (Correct Answer)
B. Parietal lobe
C. Frontal lobe
D. Occipital lobe

Explanation: ***Temporal lobe*** - Lesions in the **temporal lobe** disrupt the **Meyer's loop**, which carries contralateral inferior retinal (superior visual field) fibers. - This specific disruption leads to a **contralateral homonymous upper quadrantanopia**, affecting the upper visual field on the side opposite the lesion [1]. *Parietal lobe* - Lesions in the **parietal lobe** typically cause a **contralateral homonymous inferior quadrantanopia**. - This is because the parietal optic radiations carry fibers from the contralateral superior retina (inferior visual field) [1]. *Frontal lobe* - The **frontal lobe** is primarily involved in **eye movements** and **saccades**, not direct processing of visual fields. - Lesions here might cause gaze preferences or motor deficits, but generally not specific quadrantanopias. *Occipital lobe* - Lesions in the **occipital lobe**, especially the visual cortex, result in **contralateral homonymous hemianopia** with **macular sparing** [1]. - A quadrantanopia from an occipital lesion would typically be inferior, and a complete hemianopia is more common.

Question 377: A fracture of the middle cranial fossa may result in an injury of the

A. Sixth cranial nerve (Correct Answer)
B. Tenth cranial nerve
C. Eighth cranial nerve
D. Eleventh cranial nerve

Explanation: ***Sixth cranial nerve*** - The **abducens nerve (CN VI)** passes through the **Dorello's canal (or petroclival ligament)**, located in the vicinity of the middle cranial fossa. - Fractures in this region can lead to **stretching or compression** of the abducens nerve, resulting in **lateral rectus palsy** and *diplopia*. *Tenth cranial nerve* - The **vagus nerve (CN X)** exits the skull via the **jugular foramen**, located in the **posterior cranial fossa**. - Injury to this nerve is less likely with a fracture specifically confined to the middle cranial fossa. *Eighth cranial nerve* - The **vestibulocochlear nerve (CN VIII)** courses through the **internal auditory meatus** in the **petrous part of the temporal bone**, which is part of the posterior cranial fossa. - While acoustic trauma or petrous bone fractures can affect it, it's not a primary concern with general middle cranial fossa fractures. *Eleventh cranial nerve* - The **spinal accessory nerve (CN XI)** exits the skull through the **jugular foramen**, similar to the vagus nerve, placing it in the **posterior cranial fossa**. - Damage to this nerve would primarily cause weakness in the **sternocleidomastoid** and **trapezius muscles**, and is not typically associated with isolated middle cranial fossa fractures.

Question 378: Which one of the following cranial nerves does NOT supply the external ear?

A. Cranial nerve V
B. Cranial nerve IX
C. Cranial nerve VII
D. Cranial nerve VI (Correct Answer)

Explanation: ***Cranial nerve VI*** - Cranial nerve VI, the **abducens nerve**, solely innervates the **lateral rectus muscle** of the eye, responsible for eye abduction. - It has no known role in the sensory or motor innervation of the external ear. *Cranial nerve V* - The **auriculotemporal nerve**, a branch of the **mandibular division of the trigeminal nerve (V3)**, provides sensory innervation to the anterior aspect of the external ear and the temporomandibular joint. - Therefore, cranial nerve V contributes to the innervation of the external ear. *Cranial nerve IX* - The **glossopharyngeal nerve (IX)** contributes to the innervation of the external ear through its **auricular branch**, which supplies a small area of skin near the external auditory meatus. - This provides some sensory input from the external ear. *Cranial nerve VII* - The **facial nerve (VII)** supplies motor innervation to the **auricular muscles** and provides sensory innervation to a small area of the concha via the **nervus intermedius**. - Its involvement is evident in various reflexes and sensations related to the ear.

Question 379: A 50-year-old male patient presented with left -sided hemiparesis. Damage to which part of the internal capsule leads to this presentation?

A. Anterior limb
B. Posterior limb (Correct Answer)
C. Retrolentiform
D. Sublentiform

Explanation: Posterior limb - The posterior limb of the internal capsule contains the corticospinal tracts, which carry motor commands from the brain to the spinal cord [1]. - Damage to this area typically results in contralateral hemiparesis or hemiplegia, matching the patient's left-sided weakness. Anterior limb - The anterior limb of the internal capsule primarily contains tracts connecting the thalamus to the frontal lobe and the pontine nuclei to the cerebellum. - Lesions here typically cause dysarthria or behavioral changes, not hemiparesis. Retrolentiform - The retrolentiform part of the internal capsule carries visual (optic radiation) and auditory pathways. - Damage to this area would primarily cause contralateral visual field deficits or auditory agnosia, not motor weakness. Sublentiform - The sublentiform part of the internal capsule contains auditory radiations and temporopontine fibers. - Injury here would result in auditory symptoms or potentially aphasia if dominant hemisphere is affected, not hemiparesis.

Question 380: Which structure is supplied by the nerve causing this elevation?

A. Risorius
B. Masseter
C. Lateral rectus
D. Superior oblique (Correct Answer)

Explanation: ***Superior oblique*** - The **trochlear nerve (CN IV)** causes the elevation visible in the image at the **dorsal midbrain** level, supplying the **superior oblique muscle**. - This nerve is unique as it **decussates completely** and has the longest intracranial course, making it prone to injury. *Risorius* - The **risorius muscle** is innervated by the **facial nerve (CN VII)**, which exits at the **pontomedullary junction**. - This nerve does not cause elevations at the **dorsal midbrain** level where the arrow is pointing. *Masseter* - The **masseter muscle** is one of the muscles of mastication innervated by the **mandibular division of the trigeminal nerve (CN V)**. - The trigeminal nerve has its motor nucleus in the **pons**, not at the dorsal midbrain level where the elevation is visible in the image. *Lateral rectus* - The **lateral rectus muscle** is supplied by the **abducens nerve (CN VI)**, which exits at the **pontomedullary sulcus**. - The abducens nerve pathway does not create the elevation seen at the **dorsal midbrain** in this image.

Practice by Chapter

Cerebral Hemispheres

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Diencephalon

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Brainstem

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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

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Functional Systems and Pathways

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Applied Neuroanatomy

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Neuroimaging Correlations

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