Anatomy and clinical signs of the lesion of the glossopharyngeal nerve

1. Big picture

The glossopharyngeal nerve, cranial nerve IX, is a mixed cranial nerve of the medulla. In the exam, it is rarely tested completely alone because its clinical examination overlaps strongly with the vagus nerve, cranial nerve X. Together, CN IX and CN X are important for swallowing, gag reflex, taste from the posterior tongue, pharyngeal sensation, and autonomic reflexes from the carotid sinus and carotid body.

The examiner usually wants you to know three things:

1. CN IX provides the afferent limb of the gag reflex.

2. It carries taste and general sensation from the posterior one-third of the tongue and pharynx.

3. Its lesion causes dysphagia, loss of gag reflex, loss of posterior tongue taste/sensation, and is often associated with CN X and CN XI lesions at the jugular foramen.