The pharyngeal reflex or gag reflex is elicited by stimulating the posterior pharyngeal wall and results in bilateral contraction of the pharyngeal muscles and brief elevation of the soft palate. The sensory limb is mediated by the glossopharyngeal nerve via the petrosal ganglion. The efferent limb is mediated by the vagus nerve and glossopharyngeal nerve. The vagus nerve originates in the rostral nucleus ambiguus of the medulla, then exits the brainstem dorsolateral to the inferior olive, and exits the skull via the jugular foramen and innervates the stylopharyngeus muscle and superior pharyngeal constrictors. If there is a glossopharyngeal nerve lesion, there is no response when touching the affected side of the pharynx. If there is vagal nerve damage, the soft palate elevates and pulls toward the intact side.
Lesions of the glossopharyngeal nerve rarely occur in isolation and usually are associated with vagus and spinal accessory nerve dysfunction, manifesting as dysphagia and dysphonia, ipsilateral palatal weakness, loss of gag reflex, homolateral vocal cord paralysis, altered taste and oropharyngeal sensation, decreased parotid secretion, and sternocleidomastoid and trapezius weakness. The major causes are trauma and tumors (especially paragangliomas), metastatic lesions to the skull base, extension of mastoid infections, or autoimmune disorders, such as giant cell arteritis.
Glossopharyngeal neuralgia is a disorder characterized by paroxysms of severe unilateral pain in the tongue, throat, ear, and tonsils. Symptoms of pain typically last from seconds to a few minutes and are triggered by chewing, talking, coughing, yawning, swallowing, and eating particular foods. The etiology is often unclear, but, some cases may be due to vascular compression of the nerve. There is usually no associated impairment of the glossopharyngeal nerve (e.g., no dysphagia) or any abnormal findings on the neurologic examination. The symptomatic treatment approaches are similar to those employed for trigeminal neuralgia. Surgical decompression of the nerve or rhizotomy is a second-line option.