What is otosclerosis?

Otosclerosis is a hereditary condition that causes the abnormal growth of bone of the middle ear and inner ear. This bone prevents structures within the ear from working properly and causes hearing loss. For some people with otosclerosis, the hearing loss may become severe.

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How does otosclerosis cause hearing impairment?

Otosclerosis can cause different types of hearing loss, depending on which structure within the ear is affected. Otosclerosis usually affects the last bone in the chain, the stapes, which rests in the entrance to the inner ear (the oval window). The abnormal bone fixates the stapes in the oval window and interferes with sound passing waves to the inner ear. This causes a conductive or mechanical hearing loss, a hearing loss caused by a problem in the outer or middle ear. Less frequently, otosclerosis may cause a sensorineural hearing loss (damaged sensory cells and/or nerve fibers of the inner ear). Most patients with Otosclerosis have a combination of these problems, or a mixed hearing loss. Next commonly, patients may have a pure conductive hearing loss. The least common pattern is a sensorineural pattern which can sometimes be difficult to diagnose as it can mimic hearing loss from other causes.. Otolsclerosis may cause mild to profound hearing loss and is very variable amongst those affected.

What causes otosclerosis?

The cause of otosclerosis is not fully understood, although it is a hereditary problem, or passed down from parent to child. Many different genes seem to be involved in this problem. It can skip generations and be silent and appear to cause hearing loss in a person without a known family history of it. It can cause different severities of hearing loss amongst those affected in the family. It may be completely silent in one person, but be passed on through genetics to their children.

People who have a family history of otosclerosis are more likely to develop the disorder. On average, a person who has one parent with otosclerosis has a 25 percent chance of developing the disorder. If both parents have otosclerosis, the risk goes up to 50 percent. Research shows that white, middle-aged women are most at risk.

Some research suggests a relationship between otosclerosis and the hormonal changes associated with pregnancy. While the exact cause remains unknown, there is some evidence associating viral infections (such as measles) and otosclerosis.

What are the symptoms of otosclerosis?

Hearing loss is the most frequent symptom of otosclerosis. The loss may appear very gradually. Many people with otosclerosis first notice that they cannot hear low-pitched sounds or that they can no longer hear a whisper. In addition to hearing loss, some people with otosclerosis may experience dizziness, balance problems, or tinnitus. Tinnitus is a sensation of ringing, roaring, buzzing, or hissing in the ears or head that accompanies many forms of hearing loss.

How is otosclerosis diagnosed?

Otosclerosis is diagnosed by a careful physical examination and audiolocal testing. The acoustic reflex tests in the immitence part of the hearing evaluation are particularly important to it’s diagnosis. Sometimes the diagnosis takes a few years to establish, with serial audiograms being required when the hearing loss is mild, or the sensorinerual kind of hearing loss is present. A CT scan is occasionally used to confirm its presence.

How is otosclerosis treated?

Medical therapy is sometimes recommended. Fluoride therapy is thought to potentially prevent the development of sensorinerual hearing loss, but will not improve hearing loss that has already developed.

Hearing aids are commonly prescribed for patients with otosclerosis. A hearing aid is designed to compensate for a hearing loss by amplifying sound. An audiologist can discuss the various types of hearing aids available and make a recommendation based on the specific needs of an individual.

Surgery is an option for treatment of the conductive or mechanical hearing loss caused by otosclerosis. In an operation called a stapedectomy, or stapedotomy, an otologist (ear surgeon) bypasses the diseased bone with a prosthetic device that allows sound waves to be passed to the inner ear. It is important to discuss the risks and possible complications of this procedure, as well as the benefits, with the surgeon. In rare cases, surgery can worsen the hearing loss.

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