Otosclerosis is the abnormal growth of bone of the inner ear.
This bone prevents structures within the ear from working properly and causes hearing loss. For some people with otosclerosis, the hearing loss may become severe. Hearing is a series of events in which the ear converts sound waves into electrical signals and causes nerve impulses to be sent to the brain where they are interpreted as sound. Sound waves enter through the outer ear and reach the middle ear, where they cause the ear drum to vibrate. The vibrations are transmitted through three tiny bones in the middle ear called the ossicles.