Primary disease of bony labyrinth.

• In this disease spongy bone replaces part of dense enchondral layer of bony otic capsule.
• Most commonly involves stapes (ear bone) and causes its fixation. Exact etiology not known, but commonly having positive family history in 50% patient.
• More commonly occurs in female than males, mode of transmission autosomal dominant. Age of onset 30 year onwards.

There are three types of otosclerosis:-

Stapedial-most common.
Cochlear
Histologic

SYMPTOMS:-

• Decreased hearing.
• Otosclerotic person hearing better in noisy than quieter surrounding, Tinnitus
• Vertigo
• Monotonous, well modulated soft speech
• Carhartz notch:- In pure tone audiogram bone conduction is normal but there is in bone conduction curve which is maximum at 2000 Hz, Called Carhartz notch and dip instead of deep.

TREATMENT:-

• Medical:- Sodium fluoride used to hasten the maturity of active focus and arrest further cochlear loss.
• Surgical:- Stapedotomy with prosthesis replacement is the treatment of choice.
• Prosthesis used are Teflon, stainless steel, platinum Teflon, titanium Teflon.