By: Catherine Joachin

Cranial Nerve IX

Anatomy and Function

Cranial nerve IX, also known as the glossopharyngeal nerve, emerges from the lower part of the brainstem (medulla oblongata) and relays motor, parasympathetic, and sensory information to the mouth and throat muscles that control taste and swallowing (Cleveland Clinic, 2026).

It exits the skull through an opening known as the jugular foramen (Cleveland Clinic, 2026). Outside of the jugular foramen are two ganglia (the superior and inferior ganglia) containing the cell bodies of the sensory fibers in cranial nerve IX (Anderson, 2020). The glossopharyngeal then travels down the neck, passing behind the styloid process, descending to the stylopharyngeus muscle before finally reaching the throat (Cleveland Clinic, 2026). The styloid process is a bone associated with tongue and larynx muscles, controlling taste and swallowing, while the stylopharyngeus, which runs down the throat, helps lift the larynx and pharynx to facilitate swallowing (Cleveland Clinic, 2026).

The glossopharyngeal nerve plays a role in regulating muscles, organs, and body processes in the throat area, including salivary glands, tongue, and tonsils (Cleveland Clinic, 2026). Thus, glossopharyngeal nerve palsy, i.e., partial or complete paralysis of CN IX, which can be attributable to a stroke or post-head or neck surgery complications, can lead to important issues in this same area (Cleveland Clinic, 2026). Professional help should be sought if experiencing any of the following symptoms:

• Discomfort or inability to open the mouth
• Dry mouth
• Pain in the ears, mouth, or throat
• Reduced or lack of feeling in the back of the mouth
• Difficulty swallowing
• Weakened or absent gag reflex

(Cleveland Clinic, 2026)

Cranial Nerve Stimulation – Nerve of Hering

While damage to the glossopharyngeal nerve is unlikely to cause seizures, it remains of interest because of its neuromodulatory potential.

In fact, researchers have explored the potential for electrical stimulation of the nerve of Hering (HN), a branch of the ninth cranial nerve which innervates the carotid sinus and carotid body, as a means of controlling seizure activity. The glossopharyngeal nerve supports the carotid sinus, an area located in the neck region responsible for regulating blood pressure by draining blood from the brain into the carotid artery (Cleveland Clinic, 2026).

A less invasive technique than vagus nerve stimulation (VNS) of the tenth cranial nerve, HN stimulation would be a good treatment option for patients for whom current medical, surgical, or other neuromodulation techniques have failed (Tubbs, Patwardhan & Oakes, 2002). To date, pilot studies have reported minor side effects such as difficulty swallowing or throat hoarseness, but have observed no significant side effects for either left- or right-sided stimulation,  unlike VNS, which is restricted to the left side out of concern for cardiac side effects caused by right-sided stimulation (Tubbs, Patwardhan & Oakes, 2002). Finally, preliminary results indicate that HN stimulation can control focal seizures in most patients, suggesting that this technique could represent a therapeutic option to control refractory epilepsy (Tubbs, Patwardhan & Oakes, 2002).

Conclusion

Cranial nerve IX is a mixed sensory and motor nerve that supports important neck, throat and mouth functions. Although not yet established as a clinical treatment, glossopharyngeal nerve stimulation may be of interest to address medically and/or surgically refractory epilepsy seizures via stimulation of the nerve of Hering.

References

Anderson, T. D. (2020). 10 – Cranial Nerves IX and X: Glossopharyngeal and Vagus. In Netter’s Neurology (Third Edition, pp. 113–121). Elsevier Inc. https://doi.org/10.1016/B978-0-323-55476-3.00010-8

Glossopharyngeal Nerve: Cranial Nerve 9: Anatomy & Function. (2026). Cleveland Clinic. Retrieved July 19, 2026, from https://my.clevelandclinic.org/health/body/22269-glossopharyngeal-nerve#anatomy

Tubbs, R. S., Patwardhan, R. V., & Oakes, W. J. (2002). Ninth Cranial Nerve Stimulation for Epilepsy Control. Pediatric Neurosurgery, 36(5), 244–247. https://doi.org/10.1159/000058427