Otosclerosis is a condition in which there is an overgrowth of bone in the space behind the eardrum (middle ear) and in the inner ear. Symptoms include tinnitus (such as ringing in the ears), dizziness, and some hearing loss, with severe hearing loss (deafness) developing as the middle and inner ear become less functional.

The cause of otosclerosis is unknown, although it may be hereditary. Hearing loss from otosclerosis is usually noticed between the ages of 11 and 30. Women have otosclerosis twice as often as men. The condition may get worse during pregnancy.

Hearing loss caused by otosclerosis may sometimes be improved by surgery.