Which test corresponds to cranial nerve IX (glossopharyngeal nerve)?

The glossopharyngeal nerve, also known as cranial nerve IX, primarily has a role in both sensory and motor functions related to the throat and the back of the tongue. One of its key functions is to provide motor innervation to the stylopharyngeus muscle, which helps in swallowing, and it also contributes to the sensory component of the gag reflex.

Testing the gag reflex assesses both the sensory function (via the glossopharyngeal nerve) and the motor response related to the swallowing action. This makes the gag reflex and the ability to swallow important indicators of cranial nerve IX integrity.

In contrast, the ability to taste sweet on the anterior tongue is associated with cranial nerve VII (facial nerve), which is responsible for taste sensations from the anterior two-thirds of the tongue. Turning the head against resistance evaluates the function of cranial nerve XI (accessory nerve), which innervates the sternocleidomastoid and trapezius muscles. Symmetry of facial movements relates to cranial nerve VII as well, since it controls the muscles of facial expression.

Understanding these functions and their corresponding tests helps to clarify the roles of the various cranial nerves in both sensory and motor pathways.