Formation of spongy bone in the labyrinth capsule which can progress toward the stapes (stapedial fixation) or anteriorly toward the cochlea leading to conductive, sensorineural, or mixed hearing loss. Several genes are associated with familial otosclerosis with varied clinical signs.
Pathological condition of the bony labyrinth of the ear, in which there is formation of spongy bone; may cause bony ankylosis of the stapes, resulting in conductive hearing loss; cochlear otosclerosis may also develop, resulting in sensorineural hearing loss.