Advanced Hypoglossal Canal Quiz

Q1. Why can a lesion of the hypoglossal canal cause ipsilateral tongue weakness?

• It selectively damages taste fibers of CN VII
• It damages the lower motor neuron pathway of CN XII on that side
• It paralyzes the contralateral facial nerve
• It interrupts bilateral optic pathways

Q2. In a unilateral lower motor neuron hypoglossal lesion, toward which side does the protruded tongue typically deviate?

• Away from the side of the lesion
• Straight upward
• Posteriorly without lateral deviation
• Toward the side of the lesion

Q3. Why can chronic CN XII injury produce tongue atrophy and fasciculations?

• Denervation produces lower motor neuron changes in tongue muscles
• Loss of sensory input enlarges the tongue
• Parasympathetic denervation causes isolated taste loss
• Corticospinal injury directly causes ipsilateral fasciculations

Q4. Why should an occipital condyle fracture raise concern for CN XII injury?

• The nerve lies entirely within the orbit
• CN XII passes through the mandibular condyle
• The canal is closely related to the occipital condyle
• The canal is located in the frontal bone

Q5. Why can a skull-base mass near the hypoglossal canal cause an isolated motor speech or swallowing-related deficit?

• CN XII controls tongue muscles important for speech and bolus handling
• CN XII is the main sensory nerve of the pharynx
• The canal contains the primary taste pathway
• CN XII supplies the vocal folds directly

Q6. How can a hypoglossal canal lesion be distinguished anatomically from a jugular foramen lesion?

• The hypoglossal canal contains CN IX, X, and XI
• The jugular foramen contains only CN XII
• The two openings transmit different cranial nerve groups
• Both openings transmit exactly the same structures

Q7. Why is the hypoglossal canal important in surgery around the occipital condyle?

• The canal is remote from the condyle
• The canal lies only within the mandible
• Condylar surgery can endanger the adjacent canal and CN XII
• The canal contains the optic nerve

Q8. Why can lesions near the foramen magnum produce CN XII deficits even when the hypoglossal canal itself is not destroyed?

• CN XII rootlets traverse the posterior cranial fossa before entering the canal
• The nerve enters the skull through the stylomastoid foramen
• CN XII begins in the parotid gland
• CN XII travels through the orbit before reaching the canal

Q9. Why is imaging of the hypoglossal canal useful when evaluating unexplained unilateral tongue atrophy?

• The canal is a potential site of focal CN XII pathology
• Tongue atrophy is caused only by dental disease
• The canal contains only veins
• CN XII never passes through bone

Q10. Which statement best integrates the anatomy of the hypoglossal canal?

• It is a mandibular opening transmitting the inferior alveolar nerve
• It is a temporal canal carrying the internal carotid artery
• It integrates CN XII passage, occipital condylar anatomy, venous communication, and skull-base relationships
• It is a sphenoid canal transmitting the optic nerve