A benign tumor that develops from the Schwann cells forming the sheaths of the vestibular nerves. Vestibular schwannomas most commonly arise in or immediately medial to the internal auditory canal; with growth, they present as a cerebellopontine angle mass.
Patients usually complain of a unilateral hearing loss accompanied by tinnitus and, occasionally, disequilibrium. Large tumors may also affect cranial nerves V and lower and may produce hydrocephalus. Since physical examination may disclose only a unilateral or asymmetric hearing loss, assessing cranial nerve function is mandatory.
A complete audiogram generally shows an asymmetric sensorineural hearing loss with disproportionately poor speech discrimination scores. The acoustic reflex may be absent or may show abnormal decay, and rollover may be found on performance intensity function testing for phonetically balanced words (see under TESTS OF AUDITORY FUNCTION, below). Auditory brain stem response testing shows abnormalities consistent with a retrocochlear lesion. Radiologic investigation consists of contrast-enhanced CT scan or MRI directed toward the cerebellopontine angle and the internal auditory canals.
Treatment of acoustic tumors in the elderly is controversial. Complete surgical excision, as performed in younger patients, is recommended by some surgeons, while others believe that a palliative subtotal resection is wiser. Radiation therapy (eg, with a gamma knife or linear accelerator [LINAC]) may be an alternative in selected cases. The tumor’s size, its associated symptoms, and the patient’s overall medical condition should be considered when deciding on appropriate therapy.