Otosclerosis is a common cause of hearing impairment and is hereditary. Someone in earlier generations of a family had the condition and passed it down. Similarly, immediate descendants may inherit this tendency, although the hearing impairment may not manifest itself for a generation or two. Because it is hereditary, other diseases such as scarlet fever, ear infection, and influenza have no relationship to the development of otosclerosis.
Hearing Impairment from Otosclerosis
If we were able to examine the inner ear bone under a microscope before a hearing impairment developed, we would see minute areas of both softening and hardening of the bone. This process may spread to the stapes, the inner ear, or to both these areas.
When otosclerosis spreads to the inner ear a sensorineural hearing impairment may result due to interference with the nerve function. This nerve impairment is called cochlear otosclerosis, and once it develops it is permanent. In selected cases, medication may be prescribed in an attempt to prevent further nerve impairment. On occasion, the otosclerosis may spread to the balance canals and may cause episodes of unsteadiness.
Usually otosclerosis spreads to the stapes or stirrup bone, the final link in the middle ear transformer chain. The stapes rests in a small groove, the oval window, in intimate contact with the inner ear fluids. Anything that interferes with its motion results in a conductive hearing impairment. This type of impairment is 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 careful hearing tests.
Sensorineural impairment is the term used to describe hearing losses, which result from disturbances or defects in the inner ear and/or hearing nerve transmission. These impairments may be congenital (present at birth), hereditary (genetic), or developmental, or a combination of these. Fortunately, only one in 100 children with a sensorineural impairment will show a progression of the impairment over time.
There is no local treatment to the ear itself or any medication that will improve the hearing in persons with otosclerosis. In some cases, medication or supplements may be helpful in preventing further loss of hearing.
The stapes operation (stapedectomy) is recommended for patients with otosclerosis who are candidates for surgery. This operation is performed under local anesthesia, and requires a short period of hospitalization and convalescence. Over 97 percent of these operations are successful in permanently restoring the hearing.
Stapes Operation (Stapedectomy)
Stapedectomy is performed through the ear canal under local anesthesia. At times an incision may be made above the ear to remove muscle tissue for use in the operation.
Under high-powered magnification, the eardrum membrane is turned forward and the fixed stapes partially or completely removed. The stapes may be removed with instruments, a drill, or in some cases, a laser. A prosthesis is inserted to replace it. The eardrum membrane is then replaced in its normal position. The hearing improvement obtained is usually permanent.
Hearing Improvement Following Stapes Surgery
Hearing improvement may or may not be noticeable at surgery. If the hearing improves at the time of surgery, it usually regresses in a few hours due to swelling in the ear. Improvement in hearing may be apparent within three weeks of surgery. Maximum hearing, however, is obtained in approximately four months.
The degree of hearing improvement depends on how the ear heals. In 98 percent of patients, the ear heals perfectly and hearing improvement is as anticipated. In some, the hearing improvement is only partial or temporary. In these cases the ear usually may be re-operated upon with a good chance of success.
In 2 percent of the cases, the hearing may be further impaired due to the development of scar tissue, infection, blood vessel spasms, irritation of the inner ear, or a leak of the inner ear fluid (fistula).
In less than 1 percent, complications in the healing process may be so great that there is a severe loss of hearing in the operated-on ear, to the extent that one may not be able to benefit from a hearing aid in that ear. For this reason, the poorer hearing ear is usually selected first for surgery.
Most patients with otosclerosis notice tinnitus (head noise) to some degree. The amount of tinnitus is not necessarily related to the degree or type of hearing impairment.
Tinnitus develops due to irritation of the delicate nerve endings in the inner ear. Since the nerve carries sound, this irritation is manifested as ringing, roaring, or buzzing. It is usually worse when the patient is fatigued, nervous, or in a quiet environment.
Following the successful stapedectomy, tinnitus is often decreased in proportion to the hearing improvement.
If a person is a suitable candidate for surgery, he/she is also suitable to benefit from properly fitted hearing aids. If you have stapedial otosclerosis and are not suitable for stapes surgery, or have cochlear otosclerosis, you still may benefit from a properly fitted hearing aid.
Fortunately, patients with otosclerosis very seldom go “totally deaf”, but will be able to hear with electronic aid.