Fact Friday: CATaloging the Cranial Nerves - The Glossopharyngeal 9
CATaloging the Cranial Nerves: The Glossopharyngeal 9
The glossopharyngeal is basically that guy in every high school movie you’ve ever seen. Strong (has some important motor responsibilities, sensitive (lots of sensory input) and a little mysterious (really can’t assess well at bedside). He probably has good hair too.
The glossopharyngeal provides motor innervations to the Stylopharyngeus, which lifts up the entire pharyngeal wall and assists with the relaxing and opening of the cricopharyngeus. It is responsible for all sensation, including taste, to the posterior 1/3 of the tongue and pain/touch/temperature to the muscosa of the soft palate and upper pharynx, as well as innervation to the parotid saliva glands.
Because of the close proximity to the Vagus (why does the Vagus ALWAYS gotta be involved? Diva!) as well as the multiple cross innervations, it is impossible to test the glossopharyngeal by itself at bedside. Which doesn’t really matter, because isolated lesions to this nerve are basically nonexistant.
Historically, often this nerve was “tested” by assessing gag reflex, because of the sensory innervation in provides to the upper pharynx and posterior tongue, but it’s not accurate since the MOTOR component of the gag is provided by the Vagus (Vagus AGAIN!)-so if there is “no gag” present, we don’t really know if it’s because the sensation or motor is impaired. (Plus: see other posts on the usefulness of testing the gag anyway.)
The glossopharyngeal nerve can be the good boy of the group-helpful to others, probably wears a nice sweater and has secret crush on the quirky, smart girl. Read the links below for more information!
The Neurology of Swallowing | Neurology of Swallowing (wordpress.com)
Cranial Nerves IX and X: The Glossopharyngeal and Vagus Nerves - Clinical Methods - NCBI Bookshelf (nih.gov)
Glossopharyngeal Nerve: Anatomy, Function, Treatment (verywellhealth.com)