Otosclerosis describes a condition of abnormal growth in the tiny bones of the middle ear, which leads to a fixation of the stapes bone. The stapes bone must move freely for the ear to work properly and hear well.
Hearing is a complex process. In a normal ear, sound vibrations are funneled by the outer ear into the ear canal where they hit the ear drum. These vibrations cause movement of the ear drum that transfers to the three small bones of the middle ear, the malleus (hammer), incus (anvil) and stapes (stirrup). When the stapes bone moves, it sets the inner ear fluids in motion, which, in turn, start the process to stimulate the auditory (hearing) nerve. The hearing nerve then carries sound energy to the brain, resulting in hearing of sound. When any part of this process is compromised, hearing is impaired.
It is estimated that 10% of the adult Caucasian population is affected by otosclerosis. The condition is less common in people of Japanese and South American decent and is rare in African Americans. Overall, Caucasian, middle-aged women are most at risk.
The hallmark symptom of otosclerosis, slowly progressing hearing loss, can begin anytime between the ages of 15 and 45, but it usually starts in the early 20s. The disease can develop in both women and men, but is particularly troublesome for pregnant women who, for unknown reasons, often experience a rapid decrease in hearing ability.
Approximately 60% of otosclerosis cases are genetic in origin. On average, a person who has one parent with otosclerosis has a 25% chance of developing the disorder. If both parents have otosclerosis, the risk goes up to 50%.
Gradual hearing loss is the most frequent symptom of otosclerosis. Often, individuals with otosclerosis will first notice that they cannot hear low-pitched sounds or whispers. Other symptoms of the disorder can include dizziness, balance problems, or a sensation of ringing, roaring, buzzing or hissing in the ears or head known as tinnitus.
Because many of the symptoms typical of otosclerosis can also be caused by other medical conditions, it is important to be examined by an otolaryngologist (ear, nose and throat doctor) to eliminate other possible causes of the symptoms. After an ear exam, the otolaryngologist may order a hearing test. Based on the results of this test and the exam findings, the otolaryngologist will suggest treatment options.
If the hearing loss is mild, the otolaryngologist may suggest continued observation and a hearing aid to amplify the sound reaching the ear drum. Sodium fluoride has been found to slow the progression of the disease and may also be prescribed. In most cases of otosclerosis, a surgical procedure called stapedectomy is the most effective method of restoring or improving hearing.