9th Cranial Nerve – Glossopharyngeal nerve Lesions

Definition:

A pathological process involving the ninth cranial nerve.

Causes:

The common causes are;

brainstem lesions, trauma, cerebellopotine angle and neck tumours, polio, and Guillain Barré  syndrome.

 

Examination:

Unilateral lesions to the ninth cranial nerve do not cause any deficit due to the bilateral corticobulbar connections. Bilateral lesions result in pseudobulbar palsy. Glossopharyngeal nerve lesions produce difficulty in swallowing; impairment of taste over the posterior one-third of the tongue and palate; impaired sensation over the posterior one-third of the tongue, palate, and pharynx; an absent gag reflex; and dysfunction of the parotid gland. Episodes may be triggered by cough, sneeze, swallowing, or pressure on the tragus.

This cranial nerve can be tested by assessing the gag reflex. Instruct the patient to open their mouth and say ‘Aaah’, look for a uniform soft palate, and a mid-line uvula. Any deviation from this may be pathological. The gag reflex itself consists of gently touching the soft palate of the patient with an appropriate instrument. A normal reflex is when the patient gags upon having their palate touched. An absent gag reflex is pathological