Otosclerosis (Calcification in the Middle Ear)

In otosclerosis, new spongy bone forms in patches within the bone that houses the hearing organs of the inner ear.

The site affected most often is the oval window, where the footplate of the stirrup bone sits and passes sound vibration into the inner ear. A patch of otosclerosis there stops the stirrup bone vibrating, so sound no longer reaches the inner ear. The result is conductive hearing loss.

When these changes affect the hearing organs of the inner ear itself, the loss is of the nerve type, and that form is called cochlear otosclerosis.

How hearing works, and where it fails

Sound waves travel along the ear canal to the eardrum and make it vibrate. The three small bones of the middle ear, the hammer, the anvil and the stirrup, pass that vibration into the fluids of the inner ear. Nerve endings in the inner ear turn the sound into electrical energy, and the hearing nerve carries it to the hearing centres of the brain.

A problem anywhere along the path from the outer ear to the inner ear fluids causes conductive hearing loss. In that type the hearing organs of the inner ear are healthy, but sound does not reach them.

A loss that starts in the inner ear or the hearing nerve is called sensorineural hearing loss.

Otosclerosis can affect the inner ear as well, so both types usually appear together. That combination is called mixed hearing loss.

Treatment

Otosclerosis has no medical cure. Some treatments are used to slow the progress of the hearing loss, especially in young patients whose disease advances quickly.

Stapedectomy

In this operation the surgeon removes the stirrup bone, whose movement is restricted, and puts a prosthesis in its place to carry sound into the inner ear.

The operation is done under local or general anaesthesia. It succeeds in 90 to 95 per cent of cases, and in most patients the conductive hearing loss is corrected almost completely.

Surgery is not recommended for patients whose conductive loss is very mild, nor for patients with advanced nerve-type loss whose inner ear hearing organs are severely affected. For every other patient with otosclerosis, stapedectomy is recommended unless a serious health problem prevents it.

Hearing aids

Every patient who would benefit from the operation can also benefit from a hearing aid. Patients with otosclerosis in both ears who prefer not to have surgery are advised to use a hearing aid, so that the function of the inner ear does not decline along with the hearing.