The ninth (glossopharyngeal) nerve is both sensory and motor. Its only motor function is to the stylopharyngeus muscle. This cannot be tested clinically. The nerve supplies sensation to the tympanic cavity, the tonsils, the posterior aspect of the soft palate (as does the maxillary branch of the trigeminal nerve), the posterior third of the tongue, and the pharynx. It carries taste fibers from the posterior third of the tongue and supplies secretory fibers to the parotid gland.
How to Examine the Glossopharyngeal Nerve Sensation on the pharynx can be tested with an applicator stick that has no cotton on it.
• Compare the response of the right and left halves of the pharynx by touching them gently with the end of the stick.
• You can ask the patient whether touching the pharynx feels the same right and left, and you may provoke a gag reflex on one side, but not the other.
The motor side of this reflex is a prompt contraction of the pharynx with or without gagging. In many people pharyngeal contraction and gagging cannot be elicited from either side. Abnormalities of palatal and pharyngeal sensation are soft physical signs, and there is not a high diagnostic yield in this part of the examination. You cannot test the taste on the posterior part of the tongue.
Diseases of the ninth and tenth cranial nerves are considered together after the section on the tenth nerve.
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