Otosclerosis is a common cause of hearing loss, primarily of the conductive type. It is caused by fixation of the stirrup bone in the middle ear. The middle ear consists of the eardrum and an open chamber behind it which contains three tiny bones called the hammer (malleus), the anvil (incus), and the stirrup (stapes). Sound waves passing through the ear cause the eardrum to vibrate. This vibration is carried to the inner ear by the three bones. In the inner ear, the vibrations are converted into signals carried by the hearing nerve to the brain. Abnormal bone growth around the stapes may interfere with the its ability to vibrate and transmit the sound waves, and hearing loss is the result. Otosclerosis may in some case also cause hearing loss of the sensorineural type (nerve deafness) or a combination of the conductive and sensorineural type (mixed hearing loss). Otosclerosis is commonly hereditary. About 10 percent of the caucasian population has some form of otosclerosis, however, it is rare among other ethnic backgrounds. Women are more likely than men to suffer from otosclerosis. It is the most common cause of conductive hearing loss between the ages of 20-50 in females. There are two treatments for otosclerosis, a hearing aid or an operation called stapedectomy. The stapedectomy was pioneered by Dr. John Shea, Jr., here at the Shea Ear Clinic in the 1950’s. It is now performed worldwide in much the same way as it has been for over 50 years. The operation involves removing the disease stapes bone and replacing it with an artificial one called a prosthesis. It is an outpatient operation and is highly successful at restoring hearing.