Undiagnosed severe cochlear otosclerosis as a cause of profound hearing loss.

Otosclerosis is a disease of the human otic capsule (1). Otosclerosis is well known to the otologist, as it is the most common cause for progressive conductive hearing loss in early adulthood. As hearing loss progresses, a sensorineural component is sometimes seen, resulting in a mixed hearing loss. In 1% of cases, the disease is considered purely cochlear, presenting with a sensorineural hearing loss only, as the otosclerosis involves areas other than the footplate (1).