Ostosclerosis

There are three small bones, called ossicles, in the middle ear area that are responsible for transferring sound from the eardrum to the inner ear. They transfer sound by vibrating; the first bone in the chain, the malleus, contacts the eardrum and starts vibrating when sound waves entering into the ear canal hit the eardrum. The vibrating malleus contacts the second bone in the chain, the incus, and causes it to vibrate. The vibrating incus contacts the last bone in the chain, the stapes, and causes it to vibrate. The vibrating stapes, lastly, contacts the oval window of the cochlea and causes tiny hairs in the fluid-filled inner ear to vibrate.

Any problems with the ability to vibrate of these bones can lead to hearing loss. There is a condition called otoscelrosis, in fact, in which there is abnormal growth of bone tissue around the stapes; the consistency of the bone tissue is actually altered from hard bone to spongy immature bone. The excess growth causes the stapes to become fixed in place and completely hinders the ability of the stapes to vibrate and therefore transfer sound.

This blocking of sound transfer can lead to conductive hearing loss. In certain people suffering from otosclerosis, the auditory nerve (the nerve that is responsible for passing sound signals from the inner ear to the brain) is also damaged; the reasons for this damage are unclear, though some researchers believe that it may be due to the release of toxic enzymes into the cochlea. Sensory hearing loss associated with conductive hearing loss is called mixed hearing loss.

As far as treatment, there does not seem to be any medication that affords resolution of this problem. Hearing aids can be worn by people suffering from otosclerosis, but this is not a way to resolve the problem. The most successful treatment approach for this condition is surgery; the specific type of surgery employed for otoscelrosis is called stapedectomy. A surgeon will remove the abnormal stapes and replace it with an artificial structure; usually, no outer excisions need to be made.

The causes of otosclerosis are still shrouded in mystery. The only thing that seems certain is that people who have a family history of otosclerosis have more of a chance of developing it than others; this means that the condition is most likely hereditary. There is also evidence that viral infections could be associated with the condition. According to research, it seems that women tend to develop the condition more frequently than men and that otosclerosis may be related to certain hormonal changes that occur during pregnancy.