Otosclerosis affects which bone-

Ans. is 'a' i.e., Stapes Types of otosclerosiso Following types of otosclerosis have been described1) Fenesteral or stapedial otosclerosisIt is the most common type (80-90%) The lesion starts just in front of the oval window in an area called fissula ante fenestram99 and causes stapes footplate fixation and conductive hearing loss. Hearing loss is purely mechanical.2) Cochlear otosclerosis (Retrofenestral otosclerosis)When present, it is almost always associated with stapedial (fenestral) otosclerosis. It involves region of round window or other areas in the otic capsule. It causes mixed or sensorineural hearing loss which is believed to be toxic due to diffusion of cytotoxic enzymes into the fluid of the membranous labyrinth (In contrast to stapedial otosclerosis, where the deafness is purely mechanical and is conductive). Tinnitus is more common in cochlear otosclerosis.3) Histologic otosclerosisThis type of otosclerosis remains asymptomatic and causes neither conductive nor sensorineural hearing loss.