otosclerosis

Otosclerosis involves the abnormal formation of new bone that affects two structures within the ear, known as the cochlea and labyrinth. The cochlea is a cone-shaped tube involved in hearing, and the labyrinth is key to a person's sense of balance.

 

When new bone forms over the inner ear structures, it can prevent the bones from vibrating normally. The bones are no longer able to transmit sound waves to the cochlea, and hearing is impaired. If the labyrinth is affected, the person's sense of balance can be impaired as well.

 

The main complaint is a slowly progressive loss of hearing. Usually, but not always, both ears are affected.

 

Many cases have no known cause. In others, there is a clear family history. Osteogenesis imperfecta, a genetic disease that causes bones to be brittle, often leads to otosclerosis. There is some thought that drinking non-fluoridated water may cause a susceptible person to develop otosclerosis as well.

There seems to have been a decline in otosclerosis with fluoridation of municipal water systems. If an individual with a positive family history does not have access to fluoridated water, then fluoride tablets are beneficial.

Hearing tests generally show nerve function to be normal, but there is difficulty getting sound to the nerve through the abnormal bone formation. On the hearing tests, low frequencies are usually most severely affected. If there is some concern about nerve damage to the hearing or balance structures, a CT scan of the temporal bone can show abnormalities.