Otosclerosis is a hereditary condition that causes the abnormal changes of the bone of the middle ear and inner ear. Bony changes, called remodeling, happen continuously in human skeleton but normally should not occur in the bone that houses the inner ear, called the otic capsule. Otosclerosis causes remodeling of the otic capsule. These changes lead to hearing loss. It may occur in one or both ears and is frequently asymmetric.
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 ossicular 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 its ability to vibrate and conduct sound into the inner ear. This causes a conductive or mechanical hearing loss. If remodeling occurs in the bone adjacent to the inner ear, sensorineural hearing loss may occur. Most patients with otosclerosis have a combination of these problems, or a mixed hearing loss. Otosclerosis may cause mild to profound hearing loss and is very variable amongst those affected.
Otoclerosis is a hereditary condition with a highly variable gene frequency across the world. It is found on autopsy in 5-10 percent of Caucasians, in up to 25-30% of Southern Indians and up to 60-70% in Ethiopians. Many different genes seem to be involved in this problem. It can appear to skip generations as some people with otosclerosis have minimal hearing loss and are essentially asymptomatic but pass it on through genetics to their children. The condition can therefore cause hearing loss in a person without a known family history of it. It can also cause very different severities of hearing loss amongst those affected in the family. 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. It is more common, or more frequently diagnosed in women and tends to begin in young adult women during the child baring years or during pregnancy. Some research suggests a relationship between otosclerosis and hormonal changes.
Hearing loss is the most frequent symptom of otosclerosis. The loss may appear very gradually. Many people with otosclerosis experience tinnitus, or a noise in the ear as their first symptom. Other symptoms include a feeling of ear fullness, that the ear is blocked, sensitivity to loud noises, vertigo or imbalance.
Otosclerosis is diagnosed by a careful physical examination and audiolocal testing. A low-frequency conductive hearing loss is common, in addition to other clues. The acoustic reflex tests in the immitence part of the hearing evaluation are particularly important to its diagnosis. Sometimes the diagnosis takes a few years to establish, with serial audiograms being required when the hearing loss is mild, or only sensorineural. A CT scan is occasionally used to confirm its presence.
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. Our audiology and hearing aid professionals can discuss the various types of hearing aids available and make a recommendation based on your specific needs.
Surgery is an option for treatment of the conductive hearing loss caused by otosclerosis. In an intricate surgical procedure called a stapedectomy, or stapedotomy, the immobile stapes bone is replaced with a prosthetic device that allows the return of hearing. Our surgeons are extensively trained and experienced in this restorative procedure.
