Otosclerosis is one of the most common causes of conductive hearing loss. It is a disease of the bone labyrinthine capsule which consists of one or more otospongiotics focus due of a more vascularized bone, instead of the little vascularized encodral bone.
The etiology of this disease is still unknown and appears to have a multifactorial cause.
There is a familial disposition in 50% to 60% of patients with a dominant inheritance, but the clinical disease only occurs in 10% of patients with histologic disease. The chance of inheriting the disease from a parent which clinically manifest disease is about 20% and from a parent with histologic disease is about 10%.
Hormonal disturbances may be involved with the disease, as it is twice more common in women than in men and pregnancy coincides with a period of progression of all female patients with the disease.
Otosclerosis occurs more often in women, from 20-40 years, and is usually bilateral.
If the otosclerotic focus involves the footplate of the stapes it results in increase of the impedance to the passage of sound through the ossicular chain, producing conductive hearing loss.When otosclerotic lesions impring the coclear, permanent sensory hearing loss occurs.
Usually the patients have Willis’s paracusia that consists of a better hearing in noisy places. Tinnitus can be found in 70% of the patient but vertigo rarely occurs.
The patient complains of a bilateral and progressive hearing loss. There is often a positive family history, otoscopy is usually normal but sometimes can shows hiperemia of the promontory shining through the tympanic membrane (Schwartze’s sign) . Rinne’s test is negative ( bone conduction is better than air conduction ) , in Weber’s test the patient hears better in the diseased ear and Schwabach’s test is prolongued.
Audiometry shows a pure middle ear deafness in about 80% of the cases, occasionally a mixed deafness (15%) and exceptionally a pure sensorineural deafness (5%) . The stapedius rreflex is often suppressed due to otosclerotic fixation of the footplate.
Otosclerosis involving the footplate of the stapes can be corrected through surgical replacement of the stapes with a prosthesis (stapedectomy ). The surgery has better results in patients with pure conductive hearing loss.
Some evidence ssuggest that patients with otosclerosis involving the cochlea may have their level of hearing loss stabilized by treatment with oral sodium fluoride over prolongued periods of time, but more studies about this treatment is neccessary.
The earlier in life otosclerosis manifests itself the more rapid and unfavorable is its course. If stapedectomy is not carried out for the pure middle ear type, the deafness progresses and eventually the patient has a high grade hearing loss , bordering on total deafness.
Back to Otorrhinolaryngology
Back to Specialties
Back to Medstudents' Homepage