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Otosclerosis is the abnormal growth of bone of the middle 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.
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.
Otosclerosis usually causes a conductive 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), as well as a conductive hearing loss.
Symptoms and Diagnosis
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.
An examination by an otolaryngologist (ear, nose, and throat physician) or otologist (ear physician) is needed to rule out other diseases or health problems that may cause these same symptoms. An audiologist is a hearing health care professional who is trained to identify, measure, and rehabilitate hearing impairment and related disorders. An audiologist uses a variety of tests and procedures to assess hearing and balance function. The audiologist may produce an audiogram (a graph that shows a person's hearing sensitivity) and a tympanogram (a graph that shows how well the middle ear functions to conduct sound). Discuss these results with your audiologist/otologist.
The cause of otosclerosis is not fully understood, although research has shown that otosclerosis tends to run in families and may be hereditary, or passed down from parent to child. 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.
In many cases surgery is an option for treatment of otosclerosis. In an operation called a stapedectomy, a surgeon (otolaryngologist or otologist) 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.
If the hearing loss is mild, surgery may not be an option. Also, on occasion, some hearing loss persists after surgery. A properly fitted hearing aid may help some people with otosclerosis in situations that include persistent hearing loss. 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.