Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Hearing loss is a decrease in the ability to perceive sounds. It can be partial or total, sudden or gradual, temporary or permanent. It can affect one ear or both. In general, the risk of hearing loss increases with age.

Sound enters the ear and strikes the eardrum. This causes the eardrum to vibrate. The eardrum's vibrations are amplified through the middle ear by three tiny bones. Inside the ear, the vibrations are transformed into nerve impulses. These nerve impulses travel to the brain, where they are interpreted as sounds.

The outer ear and middle ear conduct sound. Any injury to this part of the hearing pathway is called conductive hearing loss. Sensorineural hearing loss is injury to the inner ear, eighth cranial nerve and brain. These structures produce, transmit and interpret nerve impulses.

Some of the most important causes of hearing loss in adults are:

  • Middle ear disease — A bacterial infection of the middle ear can:

    • injure the eardrum

    • disrupt the middle-ear bones

    • cause fluid buildup

  • Noise — Loud sounds can injure delicate cells within the ear. This is a form of sensorineural hearing loss. Noise-induced hearing loss can happen because of a single brief burst of an extremely loud sound. It more often results from long-term exposure to loud sounds of slightly lower intensity.

  • Otosclerosis —An abnormal overgrowth of one or more bones in the middle ear prevents the small bones from moving normally. This is a type of conductive hearing loss. Otosclerosis often runs in families.

  • Acoustic neuroma — This noncancerous tumor grows on part of the eighth cranial nerve. This nerve carries signals to the brain. Acoustic neuroma often causes dizziness and equilibrium problems in addition to gradual hearing loss.

  • Meniere's disease — This typically causes dizziness, hearing loss, ringing in the ears (tinnitus) and a sensation of fullness or stuffiness in one or both ears. Mιniθre's disease occurs when excess fluid causes swelling in the inner ear.

  • Trauma — Many types of accidents can cause hearing loss. Hearing loss can result when the eardrum is injured from the force of an explosion. Or it can result from a Q-tip that ruptures the eardrum during an attempt to clean the ear canal.

  • Sudden sensorineural hearing loss — This is a medical emergency. A person loses hearing over a period of three days or less. In most cases, only one ear is affected. The underlying problem may be a viral infection.

  • Drugs — Many prescription and nonprescription medications can damage the ear and cause hearing loss. These include:

    • Antibiotics

    • Anticancer chemotherapy drugs

    • Aspirin

    • Antimalaria drugs

  • Age — Age-related hearing loss (presbycusis) is not a single disease. Rather, it is a category for the cumulative effects of aging on the ears. Hearing loss usually begins after age 60. Both ears are affected. It is typically harder to hear high-pitched tones (women's voices, violins) than low-pitched ones (men's voices, bass guitar). Hearing loss usually occurs gradually over a period of years. The person may not realize that he or she has difficulty hearing.

  • Other causes — There are more than 100 different causes of hearing loss in adults. The most common reversible causes are severe buildup of earwax in the ear canal and acute infections of the external ear or middle ear.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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