Neuroanatomy Practice Questions

Q: Muscles spared by complete transection of the cranial part of the accessory nerve are:

Stylopharyngeus. ***Stylopharyngeus*** - The stylopharyngeus muscle is innervated by the **glossopharyngeal nerve (CN IX)**, not the cranial part of the accessory nerve. - Therefore, a complete transection of the cranial accessory nerve would spare its function. *Cricopharyngeus* - The cricopharyngeus muscle is innervated by the **pharyngeal plexus**, which receives input from the **vagus nerve (CN X)** and the cranial part of the accessory nerve. - Damage to the cranial accessory nerve would likely affect its function. *Palatopharyngeus* - The palatopharyngeus muscle is innervated by the **pharyngeal plexus**, which receives contributions from the **vagus nerve (CN X)** and the cranial part of the accessory nerve. - Its function would be compromised by a complete transection of the cranial accessory nerve. *Salpingopharyngeus* - The salpingopharyngeus muscle is innervated by the **pharyngeal plexus**, which includes fibers from the **vagus nerve (CN X)** and the cranial part of the accessory nerve. - Transection of the cranial accessory nerve would therefore affect this muscle.

Q: What does right 12th cranial nerve damage lead to?

Tongue deviation to right on protrusion. ***Tongue deviation to right on protrusion*** - Damage to the **right 12th cranial nerve (hypoglossal nerve)** causes weakness or paralysis of the **right genioglossus muscle**. - When the tongue is protruded, the **unopposed action of the left genioglossus muscle** pushes the tongue to the **right**, towards the side of the lesion. *Tongue deviation to left on protrusion* - This symptom would occur with damage to the **left 12th cranial nerve**, as the unopposed right genioglossus muscle would push the tongue to the left. - The **genioglossus muscle** is primarily responsible for tongue protrusion and moving the tongue to the opposite side. *Nasal twang to voice* - A **nasal twang** or **hypernasality** is typically associated with **palatal weakness**, often due to damage to the **vagus nerve (CN X)** or a **velopharyngeal insufficiency**. - The **hypoglossal nerve** (CN XII) does not directly control the muscles involved in soft palate movement or phonation in this manner. *Scanning speech defects* - **Scanning speech**, characterized by a slow, hesitant, and dysarthric pattern with abnormally long pauses, is a classic sign of **cerebellar dysfunction**. - It is not directly caused by isolated damage to the **hypoglossal nerve**, which primarily affects tongue movement and articulation.

Q: All of the following muscles are supplied by the accessory nerve except:

Stylopharyngeus. ***Stylopharyngeus*** - The stylopharyngeus muscle is supplied by the **glossopharyngeal nerve (CN IX)**, making it the exception. - This muscle is responsible for **elevating the pharynx and larynx** during swallowing. - **All other options are pharyngeal muscles supplied by the vagus nerve (CN X) via the pharyngeal plexus, NOT by the accessory nerve.** *Palatopharyngeus* - The palatopharyngeus muscle is supplied by the **vagus nerve (CN X)** via the **pharyngeal plexus**. - It depresses the **soft palate** and elevates the **pharynx and larynx**. - **Note:** The accessory nerve does NOT supply pharyngeal muscles. *Palatoglossus* - The palatoglossus muscle is supplied by the **vagus nerve (CN X)** via the **pharyngeal plexus**. - It elevates the **posterior part of the tongue** and depresses the **soft palate**. - **Note:** The accessory nerve does NOT supply pharyngeal muscles. *Musculus uvulae* - The musculus uvulae is supplied by the **vagus nerve (CN X)** via the **pharyngeal plexus**. - This muscle **shortens and elevates the uvula**. - **Note:** The accessory nerve does NOT supply pharyngeal muscles. **Clinical Pearl:** The accessory nerve (CN XI) actually supplies the **sternocleidomastoid** and **trapezius** muscles, not pharyngeal muscles. The cranial part of CN XI joins the vagus but does not independently innervate pharyngeal musculature.

Q: Which of the following cranial nerves is a pure sensory nerve?

CN 8. ***CN 8*** - The **vestibulocochlear nerve (CN VIII)** is a pure sensory cranial nerve responsible for **hearing** and **balance** [1]. - It consists of two main branches: the **cochlear nerve** (for hearing) and the **vestibular nerve** (for balance and spatial orientation) [1], [2]. *CN 3* - The **oculomotor nerve (CN III)** is primarily a **motor nerve**, controlling most extraocular muscles and the pupil. - It also carries **parasympathetic fibers** to the pupillary sphincter and ciliary muscles, but it is not purely sensory. *CN 5* - The **trigeminal nerve (CN V)** is a **mixed nerve**, containing both sensory and motor components. - Its sensory functions include sensation from the face, while its motor component innervates the muscles of mastication. *CN 9* - The **glossopharyngeal nerve (CN IX)** is a **mixed nerve** with diverse functions. - It carries sensory information from the posterior tongue (taste and general sensation) and pharynx, and motor fibers to the stylopharyngeus muscle, as well as parasympathetic fibers to the parotid gland.

Q: Intratemporal lesion of chorda tympani nerve results in -

Loss of taste sensations from anterior 2/3rd of tongue. Loss of taste sensations from anterior 2/3rd of tongue - The chorda tympani nerve, a branch of the facial nerve (CN VII), carries special visceral afferent (taste) fibers from the anterior two-thirds of the tongue. - An intratemporal lesion of the chorda tympani will result in loss of taste sensation from the anterior two-thirds of the tongue, which is a clinically significant and easily detectable finding [1]. - The chorda tympani exits the facial canal through the petrotympanic fissure and travels through the middle ear (intratemporal course) before joining the lingual nerve. Loss of secretomotor fibers to the submandibular salivary gland - While the chorda tympani also carries parasympathetic secretomotor fibers to the submandibular and sublingual salivary glands, this function is less clinically apparent. - Although secretomotor loss does occur with an intratemporal lesion, both taste loss and secretomotor loss occur together, but the question format requires selecting the most clinically significant and testable consequence. - In standard medical examinations, taste loss from the anterior 2/3 of tongue is the classic association tested with chorda tympani lesions. Loss of taste sensations from posterior 1/3rd of tongue - Taste sensation from the posterior one-third of the tongue is carried by the glossopharyngeal nerve (CN IX), not the chorda tympani. - An intratemporal lesion of the chorda tympani would not affect this region. Loss of taste sensations from papillae of tongue - This option is too vague and non-specific. - While taste loss does affect taste papillae, this option doesn't specify which part of the tongue, making it imprecise compared to the specific anatomical distribution (anterior 2/3) affected by the chorda tympani [1].

Q: The facial nerve supplies motor fibers to which of the following muscles?

Stapedius. ***Stapedius*** - The **facial nerve (CN VII)** provides motor innervation to the **stapedius muscle**, which plays a role in dampening loud sounds by pulling the stapes away from the oval window. - Dysfunction of this innervation can lead to **hyperacusis** (increased sensitivity to sound). *Mylohyoid* - The **mylohyoid muscle** is innervated by the **nerve to mylohyoid**, which is a branch of the **inferior alveolar nerve** (a branch of the mandibular division of the trigeminal nerve, CN V3). - It forms the floor of the mouth and elevates the **hyoid bone** and tongue during swallowing and speaking. *Anterior belly of the digastric* - The **anterior belly of the digastric muscle** is innervated by the **nerve to mylohyoid**, a branch of the **inferior alveolar nerve** (CN V3). - This muscle helps in depressing the mandible and elevating the hyoid bone. *Geniohyoid* - The **geniohyoid muscle** is innervated by fibers from the **C1 spinal nerve** that travel briefly with the **hypoglossal nerve (CN XII)**. - It elevates and protracts the hyoid bone, aiding in swallowing.

Q: Which one of the following structures is not a part of the auditory pathway?

Medial lemniscus. ***Medial lemniscus*** - The **medial lemniscus** is a major ascending sensory pathway responsible for transmitting **fine touch, vibration, and proprioception** from the body to the cerebral cortex [2]. - It is part of the **somatosensory system** and does not play a role in auditory processing. *Lateral lemniscus* - The **lateral lemniscus** is a key ascending auditory pathway in the brainstem that transmits information from the **cochlear nuclei** to higher auditory centers [1]. - It plays a crucial role in the processing of **auditory information**, including sound localization. *Inferior colliculus* - The **inferior colliculus** is a principal nucleus in the midbrain that serves as a major integrative and relay center for virtually all **auditory information** ascending from lower brainstem nuclei [1]. - It is involved in **sound localization**, frequency discrimination, and the startle reflex. *Medial geniculate body* - The **medial geniculate body (MGB)** is the auditory nucleus of the **thalamus** that serves as a crucial relay station for auditory information between the **inferior colliculus** and the primary auditory cortex [1]. - It is involved in various aspects of auditory processing, including **sound localization** and attention.

Q: Which of the following nuclei of the vagus receives special and general visceral afferents?

Nucleus of Solitary Tract. ### Nucleus of Solitary Tract - The **nucleus of the solitary tract** (NST) is the primary sensory nucleus for **general visceral afferents** (GVA) and **special visceral afferents** (SVA) from the vagus nerve (CN X) [1], [2]. - It receives taste sensation from the **epiglottis** and upper esophagus (SVA) and general sensation from the pharynx, larynx, and thoracic/abdominal viscera (GVA) [1], [2]. *Dorsal Nucleus of Vagus* - The **dorsal nucleus of the vagus** is primarily an **efferent (motor)** nucleus, providing **preganglionic parasympathetic innervation** to thoracic and abdominal viscera. - While it plays a role in visceral function, it is not the primary recipient of **afferent sensory information** from the vagus nerve. *Nucleus Ambiguous* - The **nucleus ambiguous** is a **motor nucleus** that provides **branchiomotor innervation** to muscles of the pharynx and larynx via the vagus nerve. - It is involved in processes like swallowing and speech, but it does **not receive visceral afferent input**. *Spinal nucleus of trigeminal nerve* - The **spinal nucleus of the trigeminal nerve** processes **pain and temperature sensation** for the face and oral cavity, primarily from the trigeminal nerve (CN V). - It is **not associated with the vagus nerve's visceral afferent functions**.

Q: In adults, the spinal cord normally ends at what level?

Lower border of L1. ***Lower border of L1*** - In adults, the **spinal cord** typically terminates at the level of the **L1 vertebral body**, or specifically, its lower border [1]. - This marks the anatomical transition from the solid spinal cord to the **conus medullaris**, which then continues as the **cauda equina** [1]. *Lower border of L3* - While the spinal cord in **newborns** can extend as low as L3, it retracts with growth, and this level is incorrect for adults. - An adult spinal cord ending at L3 would be considered an **abnormal finding**, potentially indicating a **tethered cord syndrome**. *Lower border of S1* - The spinal cord never extends to the S1 level in healthy individuals, even in newborns. - The **sacrum (S1-S5)** is well below the normal termination point of the spinal cord. *Lower border of L5* - The spinal cord typically terminates well above L5 in adults. - The **cauda equina**, not the spinal cord itself, extends through the lumbar and sacral regions to L5 and beyond.

Q: The fibers from the contralateral nasal hemiretina project to the following layers of the lateral geniculate nucleus:

Layers 1, 4 & 6.. ***Layers 1, 4 & 6.*** - The **contralateral nasal hemiretina** projects to layers 1, 4, and 6 of the lateral geniculate nucleus (LGN) [1]. - These layers receive input from the **magnocellular (layer 1)** and **parvocellular (layers 4 and 6)** pathways originating from the contralateral eye. *Layers 2, 3 & 5.* - This option incorrectly combines layers from both contralateral and ipsilateral projections. - Layers 2, 3, and 5 receive input from the **ipsilateral temporal hemiretina**, not the contralateral nasal hemiretina [1]. *Layers 1, 2 & 6.* - While layers 1 and 6 receive contralateral input, layer 2 specifically receives input from the **ipsilateral eye**. - This combination is not exclusively for contralateral nasal hemiretinal projection. *Layers 4, 5 & 6.* - This option includes layer 5, which receives input from the **ipsilateral temporal hemiretina**. - Layers 4 and 6 do receive contralateral input, but layer 5 makes this answer incorrect for an exclusive contralateral projection.

Question 1

Muscles spared by complete transection of the cranial part of the accessory nerve are:

Accepted Answer

Stylopharyngeus

Answer

Cricopharyngeus

Answer

Palatopharyngeus

Answer

Salpingopharyngeus

Question 2

What does right 12th cranial nerve damage lead to?

Accepted Answer

Tongue deviation to right on protrusion

Answer

Scanning speech defects

Answer

Tongue deviation to left on protrusion

Answer

Nasal twang to voice

Question 3

All of the following muscles are supplied by the accessory nerve except:

Accepted Answer

Stylopharyngeus

Answer

Palatopharyngeus

Answer

Musculus uvulae

Answer

Palatoglossus

Question 4

Which of the following cranial nerves is a pure sensory nerve?

Accepted Answer

CN 8

Answer

CN 3

Answer

CN 5

Answer

CN 9

Question 5

Intratemporal lesion of chorda tympani nerve results in -

Accepted Answer

Loss of taste sensations from anterior 2/3rd of tongue

Answer

Loss of secretomotor fibers to the submandibular salivary gland

Answer

Loss of taste sensations from posterior 1/3rd of tongue

Answer

Loss of taste sensations from papillae of tongue

Question 6

The facial nerve supplies motor fibers to which of the following muscles?

Accepted Answer

Stapedius

Answer

Mylohyoid

Answer

Anterior belly of the digastric

Answer

Geniohyoid

Question 7

Which one of the following structures is not a part of the auditory pathway?

Accepted Answer

Medial lemniscus

Answer

Inferior colliculus

Answer

Medial geniculate body

Answer

Lateral lemniscus

Question 8

Which of the following nuclei of the vagus receives special and general visceral afferents?

Accepted Answer

Nucleus of Solitary Tract

Answer

Dorsal Nucleus of Vagus

Answer

Nucleus Ambiguous

Answer

Spinal nucleus of trigeminal nerve

Question 9

In adults, the spinal cord normally ends at what level?

Accepted Answer

Lower border of L1

Answer

Lower border of L3

Answer

Lower border of S1

Answer

Lower border of L5

Question 10

The fibers from the contralateral nasal hemiretina project to the following layers of the lateral geniculate nucleus:

Accepted Answer

Layers 1, 4 & 6.

Answer

Layers 4, 5 & 6.

Answer

Layers 2, 3 & 5.

Answer

Layers 1, 2 & 6.

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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