Isolated lesions of either the glossopharyngeal or vagus nerves are unusual. As noted earlier, glossopharyngeal nerve abnormalities may be clinically undetectable unless adjacent structures are also involved. Perhaps the most common vagus nerve lesion is that involving the recurrent laryngeal nerve, resulting in ipsilateral vocal cord paresis and hoarseness of voice. The left nerve has a longer course, with its looped recurrence in the chest rather than in the neck, as on the right. The nerve passes around the aorta before returning rostrally to the larynx. The left recurrent laryngeal nerve may be compromised by an expanding aortic arch aneurysm or other intrathoracic processes, such as enlargement of the left atrium of the heart, pulmonary neoplasm, or mediastinal adenopathy. Both right and left superior or recurrent laryngeal nerves may be injured during the course of neck surgery such as thyroidectomy. Vocal cord paralysis has been described with vagal neuropathy attributed to diabetes or alcohol consumption, and with vagal neuritis in association with herpes simplex and herpes zoster. y Superior laryngeal branch neuralgia produces pain in the area of the thyroid cartilage radiating to the ear, and it is triggered by talking or swallowing. This is a rare disorder; treatment is with carbamazepine. Immaturity of the cervical vagus fibers may play a role in sudden infant death syndrome. y
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