Otosclerosis is a common cause of hearing impairment and is often hereditary. Someone in earlier generations of your family may have had the condition and passed it down to you. Otoscleroisis causes hearing loss that is typically noticed at middle age and affects females twice as likely as males.
Function of the Normal Ear
The ear is divided into three parts: the external ear, the middle ear, and the inner ear. Each part performs an important function in the process of hearing. Sound waves pass through the ear canal of the external ear and vibrate the eardrum, which separates the external ear from the middle ear. The three small bones in the middle ear act to transmit energy of the sound vibrations to the fluids of the inner ear. Vibrations in this fluid stimulate delicate nerve fibers. The auditory nerve then transmits impulses to the brain where they are interpreted as understandable sounds.
Types of Hearing Impairment
The external ear and the middle ear conduct sound; the inner ear receives it. If there is some difficulty in the external or middle ear, a conductive loss occurs. If trouble lies in the inner ear, a sensorineural or nerve hearing loss is the result. When there is difficulty in both the middle and inner ear, a combination of both sensorineural loss and conductive loss, or mixed hearing loss, occurs.
Hearing Impairment from Otosclerosis
An examination of the ear under a microscope often shows signs of otosclerosis before hearing loss develops. Signs include minute areas of both softening and hardening of the bone.
Cochlear Otosclerosis: When otosclerosis spreads to the inner ear, a sensorineural hearing loss may result due to interference with the nerve junction. This nerve impairment is called cochlear otosclerosis and once it develops, it may be permanent. In selected cases, medication may be prescribed in attempt to prevent further nerve impairment. On occasion, otosclerosis may spread to the balance canals and cause episodes of unsteadiness.
Stapedial Otosclerosis: Usually otosclerosis spreads to the stapes, the final link in the middle ear transformer chain. The stapes rests in a small groove called the round window, in intimate contact with the inner ear fluids. Anything that interferes with its motion results in a conductive hearing impairment called stapedial otosclerosis and is usually correctable by surgery. The amount of hearing loss due to involvement of the stapes and the degree of nerve impairment present can be determined only by hearing tests.
Treatments for Otosclerosis
Medical: There is no local treatment to the ear itself or any medication that will improve the hearing in persons with otosclerosis. In some cases, however, medication may be helpful in preventing further loss of hearing.
Surgical: An operation of the stapes (stapedectomy) is recommended for patients with otosclerosis who are surgical candidates. This operation is usually performed under local anesthesia and requires minimal hospitalization. Over 90 percent of stapedectomies are successful in restoring the hearing permanently.
Hearing Aids: For patients with otosclerosis who are not surgical candidates or do not proceed with surgery, hearing aids are beneficial. Fortunately, patients with otosclerosis very seldom go “totally deaf” and find hearing aids helpful.