Neuroanatomy — MCQs
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Which of the following cells is not present in the cerebellum?
A 64-year-old man presented to the clinic with a severely painful rash and skin eruptions localized entirely on one side of his body, closely following the dermatome level of spinal nerve C7, and was diagnosed with herpes zoster virus. In which structure has the virus most likely proliferated to cause the patient's current condition?
The facial nerve's first branch is?
Which tract fibers pass through the genu of the internal capsule?
Which of the following cranial nerves is NOT involved in superior orbital fissure syndrome?
Pain of stylalgia is mediated through which nerve?
What will be the consequence if the left optic nerve is severed?
Paralysis of the 3rd, 4th, and 6th nerves, with involvement of the ophthalmic division of the 5th nerve, localizes the lesion to:
Sensory fibers from the taste buds in the back of the tongue and soft palate travel along:
Neuroanatomy Indian Medical PG Practice Questions and MCQs
Question 1811: Which of the following cells is not present in the cerebellum?
- A. Stellate cells
- B. Basket cells
- C. Pyramidal cells (Correct Answer)
- D. Purkinje cells
Explanation: ### Pyramidal cells - Pyramidal cells are **excitatory neurons** found in the **cerebral cortex** and **hippocampus**, characterized by their triangular cell bodies and prominent apical dendrites. - They are not present in the cerebellum, which has its own distinct neuronal architecture. *Purkinje cells* - **Purkinje cells** [1] are large, flask-shaped neurons with extensive dendritic trees located in the **cerebellar cortex** [1]. - They are the **sole output neurons** of the cerebellar cortex, providing inhibitory projections to the deep cerebellar nuclei [1]. *Stellate cells* - **Stellate cells** are small **inhibitory interneurons** located in the **molecular layer** of the cerebellar cortex [1]. - They synapse onto the dendrites of Purkinje cells, modulating their activity [1]. *Basket cells* - **Basket cells** are another type of **inhibitory interneuron** found in the **molecular layer** of the cerebellar cortex [1]. - They form characteristic **basket-like plexuses** around the cell bodies of Purkinje cells, exerting powerful inhibition [1].
Question 1812: A 64-year-old man presented to the clinic with a severely painful rash and skin eruptions localized entirely on one side of his body, closely following the dermatome level of spinal nerve C7, and was diagnosed with herpes zoster virus. In which structure has the virus most likely proliferated to cause the patient's current condition?
- A. The sympathetic chain
- B. The dorsal root ganglion of the C7 spinal nerve (Correct Answer)
- C. The lateral horn of the C7 spinal cord segment
- D. The posterior cutaneous branch of the dorsal ramus of C7
Explanation: ***The dorsal root ganglion of the C7 spinal nerve*** - After primary infection (chickenpox), the **varicella-zoster virus (VZV)** lies dormant in the **dorsal root ganglia** [1]. - Reactivation occurs in these ganglia, leading to viral proliferation and axonal transport down the sensory nerves to the skin, causing the characteristic **dermatomal rash** of herpes zoster [1]. *The sympathetic chain* - The sympathetic chain primarily contains **autonomic postganglionic neurons** and is not the site of VZV latency or reactivation. - Reactivation in the sympathetic chain would lead to autonomic dysfunction, not the dermatomal rash seen in herpes zoster. *The lateral horn of the C7 spinal cord segment* - The **lateral horn** contains **preganglionic sympathetic neurons** and is part of the autonomic nervous system. - Herpes zoster specifically affects **sensory neurons**, not autonomic neurons located in the lateral horn. *The posterior cutaneous branch of the dorsal ramus of C7* - This nerve branch is a peripheral nerve that carries **sensory information** from the skin but is not the primary site of viral latency or initial reactivation. - The virus travels *to* this branch from the dorsal root ganglion to produce the rash.
Question 1813: The facial nerve's first branch is?
- A. Greater petrosal nerve (Correct Answer)
- B. Lesser petrosal nerve
- C. Chorda tympani nerve
- D. Nerve to stapedius
Explanation: ***Greater petrosal nerve*** - The **greater petrosal nerve** is the **first major branch** of the facial nerve, emerging from the geniculate ganglion. - It carries **preganglionic parasympathetic fibers** to the pterygopalatine ganglion, which innervates the lacrimal gland and glands of the nasal and palatal mucosa. *Lesser petrosal nerve* - The **lesser petrosal nerve** originates from the **glossopharyngeal nerve (CN IX)**, not the facial nerve. - It carries parasympathetic fibers to the **otic ganglion**, supplying the parotid gland. *Chorda tympani nerve* - The **chorda tympani nerve** is a branch of the facial nerve that arises within the **temporal bone**, but it is not the *first* branch. - It carries **taste fibers** from the anterior two-thirds of the tongue and **preganglionic parasympathetic fibers** to the submandibular and sublingual glands. *Nerve to stapedius* - The **nerve to stapedius** branches off the facial nerve within the facial canal, innervating the **stapedius muscle**. - It is a very small motor branch and arises **after** the greater petrosal nerve.
Question 1814: Which tract fibers pass through the genu of the internal capsule?
- A. Optic radiation
- B. Corticospinal
- C. Corticorubral tract
- D. Corticonuclear tract (Correct Answer)
Explanation: ***Corticonuclear tract*** - The **corticonuclear tract** (also known as the corticobulbar tract) conveys motor commands from the cerebral cortex to the motor nuclei of the **cranial nerves** in the brainstem [1]. These fibers precisely pass through the **genu of the internal capsule** [1]. - Damage to the corticonuclear tract at the genu can result in **contralateral weakness** or paralysis of the face, tongue, and pharyngeal muscles. *Optic radiation* - The **optic radiation** transmits visual information from the lateral geniculate nucleus to the primary visual cortex in the occipital lobe [3]. - These fibers typically course through the **retrolenticular** and **sublenticular parts** of the internal capsule, not the genu. *Corticospinal* - The **corticospinal tract** is responsible for voluntary motor control of the body, and its fibers pass through the **posterior limb of the internal capsule** [2]. - Lesions affecting the corticospinal tract in the posterior limb lead to **contralateral hemiparesis or hemiplegia** [1]. *Corticorubral tract* - The **corticorubral tract** connects the cerebral cortex to the red nucleus, which is involved in motor coordination and learning. - These fibers typically travel through the **midbrain**, separate from the internal capsule's genu.
Question 1815: Which of the following cranial nerves is NOT involved in superior orbital fissure syndrome?
- A. Abducens nerve (6th cranial nerve)
- B. Trochlear nerve (4th cranial nerve)
- C. Olfactory nerve (1st cranial nerve) (Correct Answer)
- D. Oculomotor nerve (3rd cranial nerve)
Explanation: ***Olfactory nerve (1st cranial nerve)*** - The **olfactory nerve (CN I)** passes through the **cribriform plate** of the ethmoid bone, not the superior orbital fissure [2]. - Its involvement is not a feature of superior orbital fissure syndrome, which affects structures passing through that fissure. *Trochlear nerve (4th cranial nerve)* - The **trochlear nerve (CN IV)** passes through the **superior orbital fissure** to innervate the superior oblique muscle [1]. - Its involvement can lead to **diplopia** and impaired downward and inward eye movement [1]. *Abducens nerve (6th cranial nerve)* - The **abducens nerve (CN VI)** travels through the **superior orbital fissure** to innervate the lateral rectus muscle [1]. - Damage to this nerve results in **esotropia** (medial deviation of the eye) and **diplopia** [1]. *Oculomotor nerve (3rd cranial nerve)* - The **oculomotor nerve (CN III)** passes through the **superior orbital fissure** and controls most extraocular muscles, as well as pupillary constriction and eyelid elevation. - Injury to CN III leads to **ptosis**, **mydriasis**, and an eye that is **down and out**.
Question 1816: Pain of stylalgia is mediated through which nerve?
- A. 9th cranial nerve (Correct Answer)
- B. 10th cranial nerve
- C. 11th cranial nerve
- D. 5th cranial nerve
Explanation: ***9th cranial nerve*** - **Stylalgia**, or Eagle syndrome, is characterized by pain along the styloid process and is often associated with an elongated styloid process or calcification of the stylohyoid ligament. - The **glossopharyngeal nerve** (9th cranial nerve) passes close to the styloid process and is frequently implicated in mediating the pain experienced in stylalgia [1]. *10th cranial nerve* - The **vagus nerve** (10th cranial nerve) primarily innervates structures in the neck, thorax, and abdomen, and is not directly responsible for pain associated with stylalgia [1]. - While it has broad sensory functions, its branches are less intimately involved with the styloid process itself compared to the glossopharyngeal nerve. *11th cranial nerve* - The **spinal accessory nerve** (11th cranial nerve) is chiefly a motor nerve, innervating the sternocleidomastoid and trapezius muscles. - It has no significant role in mediating sensory pain from the styloid process. *5th cranial nerve* - The **trigeminal nerve** (5th cranial nerve) is responsible for sensation in the face and mastication, and its branches do not directly mediate pain from the styloid process. - Though some atypical facial pain conditions exist, stylalgia pain is distinct and attributed to other cranial nerves.
Question 1817: What will be the consequence if the left optic nerve is severed?
- A. Left eye complete blindness with no effect on light reflexes.
- B. Bitemporal hemianopia due to optic chiasm involvement.
- C. Left eye complete blindness with intact direct reflex but loss of consensual reflex.
- D. Left eye complete blindness with loss of ipsilateral direct reflex and loss of contralateral consensual reflex. (Correct Answer)
Explanation: ***Left eye complete blindness with loss of ipsilateral direct reflex and loss of contralateral consensual reflex.*** - Severing the **left optic nerve** before the optic chiasm results in **complete blindness** in the left eye because all visual information from that eye is interrupted [1]. - The **ipsilateral direct light reflex** (pupillary constriction of the left eye when light is shone in the left eye) is lost because the afferent pathway from the left eye is damaged [1]. - The **contralateral consensual light reflex** (pupillary constriction of the right eye when light is shone in the left eye) is also lost because the afferent signal from the left eye cannot reach the brainstem to activate the efferent pathway to the right eye [1]. - **Note:** The right eye's direct and consensual reflexes (when light is shone in the right eye) remain intact because the right optic nerve is undamaged. *Left eye complete blindness with intact direct reflex but loss of consensual reflex.* - This is physiologically impossible. If the **optic nerve** is severed, the **afferent limb** of the pupillary light reflex is disrupted [2]. - Both the **direct reflex** (left eye stimulus → left pupil response) and the **consensual reflex** (left eye stimulus → right pupil response) depend on the same afferent pathway through the left optic nerve [1]. - You cannot have an intact direct reflex without an intact afferent pathway from that eye. *Left eye complete blindness with no effect on light reflexes.* - **Complete blindness** in the left eye would indeed occur, but the light reflexes **would be affected** because the **optic nerve** carries the afferent limb of the **pupillary light reflex** [1]. - Both the **direct** and **consensual light reflexes** involving the left eye as the stimulus eye would be lost. - This option is incorrect because it states there is "no effect" on reflexes. *Bitemporal hemianopia due to optic chiasm involvement.* - **Bitemporal hemianopia** occurs when there is damage at the **optic chiasm**, typically due to a pituitary tumor, which interrupts the crossing nasal fibers from both eyes [2]. - Severing a **single optic nerve** before the chiasm causes **monocular blindness**, not bitemporal hemianopia [2]. - The question specifically asks about optic nerve severance, not chiasm damage.
Question 1818: Paralysis of the 3rd, 4th, and 6th nerves, with involvement of the ophthalmic division of the 5th nerve, localizes the lesion to:
- A. Cavernous sinus (Correct Answer)
- B. Apex of orbit
- C. Brainstem
- D. Base of skull
Explanation: ***Cavernous sinus*** - The **cavernous sinus** contains cranial nerves **III (oculomotor)**, **IV (trochlear)**, **VI (abducens)**, and the **ophthalmic (V1)** and **maxillary (V2)** divisions of the trigeminal nerve (V). - A lesion here would therefore affect the function of most **extraocular muscles** and cause sensory disturbances in the distribution of V1, precisely matching the symptoms described. *Apex of orbit* - The **apex of the orbit** also contains cranial nerves III, IV, VI, the nasociliary branch of V1, and the optic nerve (II). - While it explains the CN III, IV, VI, and ophthalmic V involvement, a lesion at the apex of the orbit is more likely to also cause **optic neuropathy**, which is not mentioned. *Brainstem* - Lesions in the **brainstem** can affect these cranial nerves, but typically also involve long tracts (e.g., corticospinal, sensory pathways) leading to **contralateral weakness** or specific brainstem syndromes, which are not described. - Furthermore, brainstem lesions would not selectively affect the **ophthalmic division of the 5th nerve** in isolation without more widespread sensory or motor deficits in the face or body. *Base of skull* - Lesions at the **base of the skull** are broad and can affect multiple cranial nerves, but are generally less specific than a cavernous sinus lesion for this exact combination. - Involvement of CN III, IV, VI, and V1 together points more precisely to the anatomical confines of the **cavernous sinus** rather than a general base of skull lesion, which might affect other adjacent cranial nerves as well.
Question 1819: Sensory fibers from the taste buds in the back of the tongue and soft palate travel along:
- A. Facial nerve
- B. Trigeminal nerve
- C. Vagus nerve
- D. Glossopharyngeal nerve (Correct Answer)
Explanation: ***Glossopharyngeal nerve*** - The **glossopharyngeal nerve** (cranial nerve IX) innervates the **posterior one-third of the tongue** for general sensation and taste, as well as the **palatoglossal arch** and **soft palate** [1]. - This nerve carries taste sensations from taste buds located in these regions to the brainstem [1]. *Trigeminal nerve* - The **trigeminal nerve** (cranial nerve V) is primarily responsible for **general sensation** from the face, oral cavity, and anterior two-thirds of the tongue, but it does **not** carry taste fibers. - It also provides motor innervation to the muscles of mastication. *Facial nerve* - The **facial nerve** (cranial nerve VII) carries taste sensation from the **anterior two-thirds of the tongue** via the chorda tympani, not the posterior tongue or soft palate. - It also controls the muscles of facial expression. *Vagus nerve* - The **vagus nerve** (cranial nerve X) plays a minor role in taste, primarily innervating taste buds in the **epiglottis** and **pharynx**, which are not specified in this question [1]. - Its main functions include parasympathetic innervation to many visceral organs.
Practice by Chapter
Organization of the Nervous System
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Basal Ganglia
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Limbic System
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Cranial Nerves
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