Stapes ankylosis may be congenital or acquired, in which case it is refered to as otosclerosis. Otosclerosis is the most common cause of progressive conductive hearing loss in adults, and is generally manifested as nonsyndromic, delayed-onset, conductive hearing loss, but it may also affect the inner ear to cause sensorineural loss. Congenital stapes ankylosis may be difficult to differentiate from otosclerosis when the diagnosis of conductive hearing loss is delayed.