Parasympathetic Component of CN IX: Glossopharyngeal Nerve
Preganglionic parasympathetic axons extend from the inferior salivatory nucleus located in the pontine tegmentum. These fibres terminate within the otic ganglion located inferiorly to the foramen ovale of the sphenoid bone, with subsequent postganglionic fibres travelling to the parotid gland via the auriculotemporal nerve, a branch of the mandibular division of the trigeminal nerve (CN V3) (figure 9). Innervation of the parotid gland by CN IX stimulates the secretion of a watery saliva to aid digestion.
Clinical Implications
Damage to CN IX is usually as a result of trauma or laceration to the neck, or consequential of a brainstem lesion. Isolated injury to CN IX is uncommon and usually not clinically significant. The parasympathetic implication of damage to the glossopharyngeal nerve presents as dysfunction of the watery saliva secretory action of the parotid gland.