Anatomy: USMLE Q No. 6

[Cardiac Arrest]

During an examination of a 75-year-old woman, the physician notices that when the patient is asked to say “ah,” the soft palate does not move symmetrically, and the uvula deviates to the right side. This movement most likely indicates a lesion involving which of the following nerves?

A. Left glossopharyngeal (CN IX)
B. Left vagus (CN X)
C. Right hypoglossal (CN XII)
D. Right vagus (CN X)

[dr-kenzy]

salam ..

the answer is :

B. Left vagus (CN X)

cuz : if the uvula is drawn to one side this indicates a unilateral tenth nerve palsy and the uvula is drawn towards the normal side ..

[Cardiac Arrest]

Option B (Left vagus (CN X)) is correct. The pharyngeal branch of the vagus nerve (CN X) innervates all muscles of the soft palate, except the tensor veli palatini. A lesion involving the left vagus nerve would leave the muscles on the right unopposed, resulting in deviation of the uvula to the right. Innervation of the soft palate is normally tested by asking the patient to say “ah.”

Option A (Left glossopharyngeal (CN IX)) is incorrect. The glossopharyngeal nerve (CN IX) carries only sensory information from structures near the soft palate.

Option C (Right hypoglossal (CN XII)) is incorrect. The hypoglossal nerve (CN XII) innervates all muscles of the tongue, except the palatoglossus muscle. It does not affect function of the uvula.

Option D (Right vagus (CN X)) is incorrect. The right vagus nerve (CN X) is functional in the soft palate. A lesion involving the right vagus would leave the muscles on the left unopposed; hence, the uvula would deviate to the left.

[uday]

Left vagus is correct. Remenber rule of 17 ( 10th & 7th nerves pull the musce, where as 12th & 5th push it)

[f_ameer376]

thanx for the question