Makindo Medical Notes

Otosclerosis is a condition in which there's abnormal bone growth inside the ear. It's a fairly common cause of hearing loss in young adults. The Carhart notch is a notch in a bone conduction audiogram of more than 2 kHz, and was first described by Raymond Carhart, Ph.D., in 1950.

About

• A common cause of gradual hearing loss in young adults

Aetiology

• Genetic factors are involved, so the condition often runs in families.
• Infections possibly measles or autoimmune condition
• Twice as common in women

Pathophysiology

• The stapes, or stirrup bone, is the innermost of the ossicles and is the smallest bone in the body and sits in a hole or "window" into the cochlea.
• It is free to vibrate within the window, allowing transmission of sound. In otosclerosis, the bone around the base of the stapes becomes thickened and eventually fuses with the bone of the cochlea.
• This reduces normal sound transmission resulting in conductive deafness.

Clinical

• Progressive hearing loss often bilateral
• May also be associated with tinnitus. Pain is not typical.
• A person with otosclerosis usually speaks quietly unlike other hearing loss
• Normal, healthy-looking eardrum.

Investigations

• Low-frequency hearing loss on audiogram at 2000 Hz - Carhart's notch suggests Otosclerosis

Management

• Fluoride treatment has been used with good results in certain forms of otosclerosis
• Hearing aids are helpful with all kinds of conductive deafness
• Surgery: stapedotomy and a prosthetic (artificial) stapes inserted

References