Question
A 55-year-old woman with a 1-year history of left-sided tinnitus is diagnosed with a tumor of the left jugular fossa. Sialometry shows decreased production of saliva from the left parotid gland. The finding on sialometry is best explained by a lesion of the nerve that is also responsible for which of the following?
| A. |
Protrusion of the tongue
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| B. |
Taste sensation of tip of the tongue
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| C. |
Afferent limb of the gag reflex
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| D. |
Afferent limb of the cough reflex
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Show Answer
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Correct Answer � C
Explanation
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Answer C) Afferent limb of the gag reflex
Explanation:
The most common tumor of the jugular foramen is a paraganglioma (glomus jugulare), which typically presents with pulsatile tinnitus. The parotid gland is innervated by the tympanic branch of the glossopharyngeal nerve (CN IX), which exits the skull at the jugular foramen, posterior to the jugular fossa
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Protrusion of the tongue- Protrusion of the tongue is mediated by the hypoglossal nerve (CN XII) through the left and right genioglossus muscles. CN XII does not pass through the jugular foramen, but rather through the hypoglossal canal of the occipital bone.
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Taste sensation of tip of the tongue- Taste sensation of the anterior two-thirds of the tongue is supplied by the chorda tympani branch of the facial nerve (CN VII). Parasympathetic fibers from the chorda tympani also stimulate the sublingual and submandibular salivary glands, but not the parotid. Furthermore, the chorda tympani exits the skull through the petrotympanic fissure, not the jugular foramen.
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Afferent limb of the gag reflex-The afferent sensory limb of the gag reflex is formed by the glossopharyngeal nerve (CN IX) and the efferent motor limb formed by the vagus nerve (CN X). Upon irritation of the posterior pharyngeal wall, the reflex elicits elevation of the soft palate and bilateral contraction of the pharyngeal muscles.
Afferent limb of the cough reflex- The afferent impulses of the cough reflex are carried from the trachea and pharynx along the superior laryngeal nerve, which is a branch of the vagus nerve. Although the vagus nerve does pass through the jugular foramen, neither the vagus nor its branches innervate the parotid gland. The vagus nerve is, instead, responsible for increasing secretion in the gastrointestinal tract (e.g. gastric acid secretion).
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