Tumors that affect hearing include paraganglioma and vestibular schwannoma.
PARAGANGL?OMA
Tumors of the middle ear and mastoid are rare. Of these, the most common tumors are paragangliomas, derived from paraganglion tissue (eg, the carotid body). Otherwise known as glomus tumors, these benign lesions generally cause a conductive hearing loss and pulsatile tinnitus. Tumors originating in the middle ear (glomus tympanicum) are clinically evident even when small; those arising in the jugular vein at the mastoid (glomus jugulare) become clinically apparent relatively late and may produce symptoms such as paralysis of cranial nerves IX through XII.
Physical examination may reveal a pulsatile red mass in the middle ear. The integrity of the cranial nerves should be assessed. Audiometric evaluation usually documents a conductive hearing loss; in more widespread tumors, a sensorineural component may also be detected. Because of the multicentricity of these lesions, four-vessel cerebral angiography or magnetic resonance angiography may reveal other, occult growths. Glomus tumors may produce catecholamines, resulting in intermittent hypertension.
Treatment depends on the tumor’s size as well as the patient’s general medical condition. In the healthy patient, small tumors can be removed relatively easily. In the infirm patient, extensive tumors are probably best managed more conservatively. Relatively low-dose radiation therapy and arteriographic embolization are palliative and may be more appropriate in the elderly.
VEST?BULAR SCHWANNOMA
(Acoustic Neuroma)
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.