The most common cause of conductive deafness, otosclerosis is the slow formation of spongy bone in the otic capsule, particularly at the oval window. It occurs in at least 10% of the population in the United States. It commonly affects both ears and is seen in many females between the ages of 15 and 30.
Otosclerosis appears to result from a genetic factor transmitted as an autosomal dominant trait; many patients report family histories of hearing loss (excluding presbycusis). Pregnancy may trigger the onset of this condition.
Signs and symptoms
Spongy bone in the otic capsule immobilizes the footplate of the normally mobile stapes, disrupting the conduction of vibrations from the tympanic membrane to the cochlea. This causes progressive unilateral hearing loss, which may advance to bilateral deafness. Other symptoms include tinnitus and paracusis of Willis (hearing conversation better in a noisy environment than in a quiet one).
Early diagnosis is based on a Rinne test that shows bone conduction lasting longer than air conduction (normally, the reverse is true). As otosclerosis progresses, bone conduction also deteriorates.
Audiometric testing reveals hearing loss ranging from 60 db, in early stages, to total loss.
Weber’s test detects sound lateralizing to the more affected ear.
Physical examination reveals a normal tympanic membrane.
Oral fluoride, calcium, or vitamin D may help stabilize hearing loss. A hearing aid also may be used. Effective treatment consists of stapedectomy (removal of the stapes) and insertion of a prosthesis to restore partial or total hearing. This procedure is performed on only one ear at a time, beginning with the ear that has suffered greater damage. Alternative surgery includes stapedotomy (laser creation of a small hole in the stapes’ footplate, through which a wire and piston are inserted).
Postoperatively, treatment includes hospitalization for 2 to 3 days and an antibiotic to prevent infection. If surgery isn’t possible, a hearing aid (air conduction aid with molded ear insert receiver) enables the patient to hear conversation in normal surroundings, although this therapy isn’t as effective as stapedectomy.
VN:F [1.9.20_1166]Brief Summary of Otosclerosis,