AAO-HNSF Primary Care Otolaryngology Handbook

HEARING LOSS

Conductive hearing loss in an otherwise normal-appearing ear is highly suggestive of an ossicular abnormality. One common disease process affecting the ossicular chain is otosclerosis, a hereditary bone disorder seen only in the temporal bone. Otosclerosis commonly affects the footplate region of the stapes, causing the stapes to gradually lose mobility and become fixed, resulting in a conductive hearing loss. Surgical correction— stapedotomy —is available. A stapedotomy proce- dure re-establishes ossicular continuity by removing the fixed stapes and replacing it with a prosthesis between the incus and the vestibule of the inner ear. Sound vibrations can then be transmitted from the ossic- ular chain, through the prosthesis and into the inner ear, restoring the patient’s hearing. Sensorineural Hearing Loss Sensorineural hearing loss (SNHL) is the most common form of hearing loss. It is generally not treatable with surgery, although cochlear implants and other implantable hearing devices may be helpful in cases of profound sensorineural or mixed hearing loss. There are many causes of SNHL, but age-related changes to the cochlea causing presbycusis are by far the most common cause. As we age, the hair cells within the cochlea gradually deteriorate, causing a symmetric SNHL that begins in the high

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frequencies (Figure 5.3). Patients with presbycusis may also have tinnitus and difficulty with speech discrimination. Another common type of hearing loss is secondary to acoustic trauma or noise exposure . Noise exposure is common in certain indus- tries and is regulated by the U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA). Recreational use of firearms, hunting, expo- sure to industrial or military noise, power tools, or loud

Figure 5.3. Audiogram of a patient with presbycusis. Note that low- frequency thresholds are relatively normal, with a drop in thresholds at higher frequencies. Presbycusis is thought to be related to the normal cell senescence process that occurs over time and is always symmetric.

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