66 - 70 SBAs for the Final FRCA
Question 66
A patient struggling to swallow has their gag reflex tested by a well-intentioned speech and language therapist, who notes there is no gag response to touching the right posterior pharyngeal wall.
Upon touching the left posterior wall, however, the palate elevates and moves to the left.
Which of the following is the most likely location of the lesion?
- Left vagal and hypoglossal nerves
- Right glossopharyngeal nerve
- Right glossopharyngeal and vagus nerves
- Left hypoglossal and glossopharyngeal nerves
- Right hypoglossal nerve
Answer
- Right glossopharyngeal and vagus nerves
If the muscles are pulling to the left, then the problem is probably on the right.
The afferent limb of the gag reflex is via the glossopharyngeal, and the efferent is via the vagus.
The response should be bilateral, regardless of which side is touched, so there's clearly a motor problem here, in the right vagus, as the response is unilateral.
There is also no response at all when the right side is touched, meaning there's a sensory issue with the right glossopharyngeal nerve as well.
If both nerves are affected then the lesion may be in one of the brainstem nuclei that they both share.