The glossopharyngeal and vagus nerves pass through the area of the cerebellopontine angle, formed by the junction of the pons, medulla, and cerebellum, before exiting the skull through the jugular foramen. In this area, both nerves may be compromised by an expanding mass lesion, most commonly a schwannoma originating from the vestibular portion of the eighth cranial nerve within the internal auditory canal. The syndrome of a cerebellopontine angle tumor generally begins as tinnitus with hearing loss, and dysequilibrium or frank vertigo, which may be episodic. As the tumor expands, the fifth cranial nerve becomes involved, resulting in ipsilateral facial pain and numbness and loss of the corneal reflex. The cerebellum or cerebellar peduncles may become compressed, producing ataxia. Unilateral impingement upon the vagus nerve causes mild
hoarseness and asymmetrical elevation of the soft palate. Schwannoma arising from the glossopharyngeal nerve is a rare occurrence, but, interestingly, the presenting symptom of patients with this tumor is most commonly hearing loss.y This occurs because the mass emanating from the glossopharyngeal nerve is clinically silent until it has enlarged to the point that it is impinging upon adjacent structures.
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