9th Cranial Nerve – Tests for the Glossopharyngeal nerve

Definition:

The use and interpretation of medical examinations to determine the integrity and adequate function of the glossopharyngeal nerve (ninth cranial nerve).

This nerve provides the innervation for one of the special senses: taste.

Test procedure:

This cranial nerve can be tested by assessing the gag reflex, which is performed by gently stroking the patient’s back of the throat with a tongue depressor.

Following this, instruct the patient to say Ahh and assess the patient’s soft and hard palates, uvula and tongue looking for any signs of deviations and/or asymmetries.

Test findings (inc Positive & Negative results):

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.

A normal reaction to the gag reflex is for the patient to gag or wrench as the practitioner strokes the patient’s pharynx. An abnormal response to this examination would be an absent reflex.

In unilateral Glossopharyngeal nerve lesions, there will be no reflexive response when assessing the pharynx on the ipsilateral side to the damaged nerve.

If both the Vagus and Glossopharyngeal nerve are lesioned on one side, stimulation of the normal side elicits only a unilateral response, with deviation of the soft palate to that same side; with no consensual response observed. Probing the damaged side produces no response.

Considerations:

The most common causes of glossopharyngeal nerve lesions are;

  • brainstem lesions,
  • trauma
  • cerebellopotine angle & neck tumours,
  • polio
  • Guillain “Barr” syndrome