A 68-year-old woman had suffered from an infectious disorder for several weeks. Following recovery from this disorder, she experienced some loss of taste and an increase in salivation, together with pain spasms in the region of the pharynx, which extended into the ear. She also experienced some bradycardia and cardiac arrhythmia, as well as deviation of the uvula to the unaffected side.
The cranial nerve most directly involved in this deficit is
a. Cranial nerve VII
b. Cranial nerve IX
c. Cranial nerve X
d. Cranial nerve XI
e. Cranial nerve XII
Correct Answer: b. Cranial nerve IX
Explanation: The cranial nerve that was directly affected was the glossopharyngeal nerve (cranial nerve IX). This is a mixed and complex nerve containing: (1) special visceral efferents from the nucleus ambiguus that supply the stylopharyngeus muscle (for elevation of pharynx in speech); (2) special visceral afferent fibers that transmit taste impulses from the posterior third of the tongue, general visceral afferent fibers associated with the inferior ganglion whose receptors lie in the carotid sinus that regulates cardiovascular functions; (3) general somatic afferents whose cell bodies lie in the superior ganglion of cranial nerve IX, and which mediate somatosensory information, including pain from the pharynx; and (4) general visceral efferent fibers that originate in the inferior salivatory nucleus, which are preganglionic and synapse in the otic ganglion. The postganglionic fiber from the otic ganglion innervates the parotid gland and mediates, in part, salivation. Thus, when this nerve is affected by an infectious agent, it results in the constellation of symptoms presented earlier in this case.
(Afifi, pp 130–134; Gilroy, pp 590–591; Simon et al, pp 92–93.)