otosclerosis

Overgrowth of bone in the middle ear causing progressive deafness. This inherited condition is gradual in onset, developing usually before middle age. It is twice as common in women as in men.

The middle ear cavity houses the sound-conduction mechanism called the ossicular chain, consisting of three tiny bones (ossicles) that magnify vibrations received at the eardrum for onward transmission to the inner ear. In otosclerosis, extraneous growth of spongy bone immobilizes the chain, preventing the conduction of sound. Surgery is necessary to remove the diseased bone and reconstruct the ossicular chain.