Otosclerosis is an abnormal, microscopic growth of bone in the walls of the inner ear. This abnormal growth causes the stapes bone (also called the “stirrup”) to become immobile or “fixed”. Normally the stapes vibrates freely to allow the transmission of sound to the inner ear, but when it cannot move, it prevents sound waves from reaching the inner ear fluids, and hearing is impaired.
Otosclerotic bone sometimes involves other structures of the inner ear, thereby affecting the nerves of the inner ear. When this occurs it also causes a distortion or difficulty in understanding the speech of others, regardless of how loudly they talk.
Otosclerosis affects only the ears and usually involves both ears. It occurs in men and women with almost equal frequency and usually begins in the teens or early twenties. Although otosclerosis tends to run in families, there is no pattern to its heredity.
HEARING IMPAIRMENT FROM OTOSCLEROSIS
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. This 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.
TINNITUS WITH OTOSCLEROSIS
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.
TREATMENT OF OTOSCLEROSIS
There is no local treatment to the ear itself or any medication that will improve the hearing in persons with otosclerosis, although in some cases medication 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 90% of these operations are successful in restoring the hearing permanently.
THE STAPES OPERATION, STAPEDECTOMY
Stapedectomy is performed through the ear canal under local anesthesia. Under high power magnification the eardrum is turned forward and the immobile stapes partially or completely removed. The stapes may be removed with instruments, a drill, or a laser. A prosthesis is inserted to replace it. The eardrum is then replaced to its normal position.
The stapes prosthesis allows sound vibrations to again pass from the eardrum to the inner ear fluids. The hearing improvement obtained is usually permanent.
The patient may return to work in 2-3 days depending upon occupational requirements. Patients residing outside the Southern California area should plan to remain in Los Angeles for a total of three days, including the day of surgery.
One should not plan to drive a car home from the hospital. Air travel is permissible 48 hours following surgery.
Hearing Improvement Following Stapedectomy
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 3 weeks of surgery. Maximum hearing, however, is obtained in approximately four months.
The degree of hearing improvement depends on how the ear heals. In the majority 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% of the cases, the hearing may be further impaired due to the development of scar tissue, infection, blood vessels spasm, irritation of the inner ear, or a leak of inner ear fluid (fistula).
In less than 1%, complications in the healing process may be so great that there is severe loss of hearing in the operated 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 for surgery.
When further loss of hearing occurs in the operated ear, head noise may be more pronounced. Unsteadiness may persist for some time.
Risks & Complications of Stapedectomy
Dizziness is normal for a few hours following stapedectomy and many result in nausea and vomiting. Some unsteadiness is common during the first few postoperative days; dizziness on sudden head motion may persist for several weeks. On rare occasions, dizziness is prolonged.
Taste Disturbance and Mouth Dryness
Taste disturbance and mouth dryness is not uncommon for a few weeks following surgery. In 5% of the patients, this disturbance may be prolonged.
Loss of Hearing
Further hearing loss develops in 2% of the patients due to some complications in the healing process. In less than 1% this hearing loss is severe and may prevent the use of an aid in the operated ear.
Should the hearing be worse following stapedectomy, tinnitus (head noise) likewise may be more pronounced.
A perforation (hole) in the eardrum membrane is an unusual complication. It develops in less than 1% and usually is due to an infection. Fortunately, should this complication occur, the membrane may heal spontaneously. If healing does not occur, surgical repair (myringoplasty) may be required.
Weakness of the Face
A very rare complication of stapedectomy is temporary weakness of the face. This may occur as the result of an abnormality or swelling of the facial nerve.
HEARING AIDS & OTOSCLEROSIS
If you are a suitable candidate for surgery, you are also suitable to benefit from a properly fitted hearing aid. If you have otosclerosis and are not suitable for stapes surgery, you still may benefit from a properly fitted aid. Fortunately, patients with otosclerosis very seldom go “totally deaf,” but will be able to hear with an electronic aid. The older the patient, the less the tendency for further hearing loss due to the otosclerotic process.
If you are a suitable candidate for surgery and do not have the stapes operation at this time, it is advisable to have careful hearing tests repeated at least once a year.