Test Sensory Function

Examination of the glossopharyngeal nerve involves the gag reflex. The examiner may use either a tongue blade or an applicator stick. By touching the posterior third of the tongue, the soft palate, or the posterior pharyngeal wall, the examiner should elicit a gag reflex. The sensory portion of the loop is through the glossopharyngeal nerve;the motor portion is mediated through the vagus nerve.

Another way to test the nerve is to ask the patient to open the mouth widely and to say, ''Ah ... ah.'' Symmetric elevation of the soft palate demonstrates normal function of cranial nerves IX and X. The uvula should remain in the midline.

Taste sensation of the posterior third of the tongue is not routinely tested.

RIGHT

LEFT

RIGHT

LEFT

Corticobulbar fibers

Facial nerve nucleus in pons

Facial nerve to upper face

Facial nerve to lower face

Corticobulbar fibers

Facial nerve nucleus in pons

Facial nerve to upper face

Facial nerve to lower face

Figure 21-16 Innervations of the facial nerve and types of facial weakness. Lesion A produces an upper motor nerve palsy that causes contralateral weakness of the lower face but spares the contralateral forehead. Lesion B produces a lower motor nerve palsy that causes total paralysis of the ipsilateral face.

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