THE MERCK MANUAL OF GERIATRICS, Ch. 129, Ear Disorders

Section 15. Dermatologic and Sensory Organ Disorders
Chapter 129. Ear Disorders
Topics: Introduction \| Tinnitus \| Otalgia \| Cerumen Accumulation \| External Otitis \| Secretory Otitis Media \| Chronic Suppurative Otitis Media \| Cholesteatoma \| Otosclerosis \| Nonmalignant Tumors and Lesions \| Primary Malignant Tumors \| Metastatic Tumors

Otosclerosis

Otosclerosis is formation of spongy bone in the otic capsule resulting from abnormal bone resorption and new bone formation.

Geriatric Essentials

Advanced otosclerosis can lead to severe sensorineural hearing loss.

Subclinical otosclerosis (detected only by examination of the temporal bone) occurs in about 7 to 10% of whites and 1% of blacks. Only 10% of people with subclinical otosclerosis develop noticeable hearing loss. Otosclerosis tends to be hereditary; 50 to 60% of affected people have a family history of it. The measles virus has been implicated as a cause.

Usually, otosclerosis is diagnosed before old age. Prevalence increases from about 0.22/1000 in people age 20 to 30 to 3.53/1000 in those age 60. The disorder is characterized by abnormal deposition of bone, predominantly around the rim of the oval window. Eventually, the new bone traps and restricts the movement of the stapes. Left untreated, hearing loss continues after diagnosis so otosclerosis may be the cause of progressive conductive hearing loss in elderly people. Hearing loss becomes clinically significant in about 10% of people with otosclerosis. Occasionally, when the cochlea is involved, it causes sensorineural hearing loss. Sensorineural hearing loss may be profound in patients, especially elderly ones, with advanced otosclerosis.

Otosclerosis is suspected when the audiogram shows a Carhart notch (a characteristic notch at 2000 Hz). A hearing aid is an acceptable option for many patients. Surgical bypass of the stapes (stapedectomy or stapedotomy), an outpatient procedure, usually corrects conductive hearing loss. Surgery is recommended for patients who hear a 512-Hz tuning fork louder when it is applied to the mastoid than when it is held 2 to 3 cm from the ear (Rinne test). The best candidates for surgery are patients with significant conductive hearing loss, good hearing in the unaffected ear, and good motivation. Elderly patients with mixed hearing loss may benefit from stapedectomy because closing the air-bone gap in an ear with sensorineural loss may bring the hearing threshold to a level more amenable to hearing aid use. Stapedectomy or stapedotomy may help patients with profound sensorineural hearing loss hear better when using a hearing aid.

This topic was last updated June 2006.