Stapes. The stapes is the third of the three little hearing bones in the middle ear that transmit sound vibrations from the eardrum to the inner ear fluid so that we can hear. We hear when sound vibrations set the eardrum in motion. The eardrum, in turn, activates the first middle ear bone, the malleus. It, in turn, sets the second middle ear bone, the incus, in motion. It, in turn, causes the third middle ear bone, the stapes, to vibrate. The stapes sets the inner ear fluids in motion which excites the hearing nerve to carry the sound on to the brain. It is by this mechanism that we hear.
Otosclerosis. Otosclerosis refers to a growth of bone in the ear that develops around the stapes, fixing it in place so that it will not vibrate properly. This fixation stops some of the sound vibrations from reaching the inner ear fluids, therefore causing hearing loss.
Stapedectomy. Stapedectomy is an operation to remove the fixed stapes and to replace it with a prosthesis. This allows sound vibrations to be transmitted properly to the inner ear fluids for hearing.
Causes of Otosclerosis
Otosclerosis is not a cancerous growth or a tumor, but rather a somewhat self-limited growth of bone in such an area as to cause difficulty in hearing. It only occurs in the ear. Otosclerosis is hereditary and is often seen in more than one member in a family. Its hereditary nature, however, is somewhat irregular. It is not unusual to see otosclerosis only in one member of a family.
Natural Course of Otosclerosis
Otosclerosis may affect one or both ears of an individual and gradually causes progressive hearing loss as the bony growth gets larger.
The speed at which the otosclerotic bone develops in an individual one. Though it usually takes many years for a significant hearing loss to result from otosclerosis, it may develop to a point and completely stop.
Pregnancy and birth control pills may make the growth occur more rapidly. Advancing age of the individual may cause the growth to slow down. Surgery does not stop the growth of otosclerosis, but usually results in correcting the hearing loss.
The hearing loss caused by otosclerosis is usually conductive. This sort of hearing loss results from a fixation of the stapes so that it cannot conduct sound vibrations properly for hearing. Conductive hearing loss is correctable by surgery.
Otosclerosis, however, may occasionally cause a sensorineural hearing loss. In this condition, the otosclerotic involvement of the hearing nerve cells and endings prevents hearing, rather than a defect in the small bones of the middle ear sound conduction system. Sensorineural hearing loss is NOT correctable by surgery at the present time. These two types of hearing loss, conductive and sensorineural, may occur singly or together but are unrelated to one another as far as treatment is concerned.
Surgery for Otosclerosis
The conductive type of hearing loss caused by otosclerosis is usually correctable by surgery called stapedectomy. Such a hearing loss is possible to be overcome with a hearing aid. Most patients find that it is more convenient, more comfortable, and more satisfying, however, to hear naturally through their own ear rather than through a hearing aid.
Otosclerosis is not an emergency situation and surgery for otosclerosis need not be done immediately. The surgery is to help the patient to hear better. The timing for the surgery is strictly at the patient's discretion.
Preoperatively, the patient will have a hearing test just prior to or during admission to the hospital.
Surgery can be done under local anesthesia or general anesthesia. We prefer to use general anesthesia, i.e. the patient is asleep during the operative procedure. During the operative procedure the eardrum is gently lifted, the diseased and fixed stapes is removed. Next, a prosthesis is put in place. The eardrum is gently put back into place and held there by absorbable packing ointment. The operation usually takes one hour and a half.
After awakening from anesthesia, the patient is returned to his room and is usually discharged the next morning. During this immediate postoperative period, it is important NOT to blow the nose and not to get the ear wet until the ear has completely healed.
In 90 of 100 patients, the operation is completely successful, in that the hearing is markedly improved. In 8 out of 100 patients, the hearing is improved, but not quite as much as hoped for. Occasionally, about 1 or 2 times in 100 operations, the hearing is actually worse. This is why the worst hearing ear is operated on first in most situations.
It is expected that the patient will be slightly dizzy for the first day or two after the operation, but this usually resolves rapidly.
Usually, the patient may return to work and normal activity one week after leaving the hospital. The patient may also fly in pressurized aircraft on the third postoperative day.
There is a small nerve running through the middle ear, the chorda tympani nerve, which supplies taste sensation to the anterior side of the tongue. Occasionally, this nerve interferes with the successful completion of the stapedectomy surgery and is removed. Other times, it may be stretched to allow good visualization to perform the surgery. This is often not noticed by the patient. However, there are instances in which the patient may notice that there is some lack of taste of that side of the tongue or that there is a strange metallic taste. This sensation of a metallic taste usually disappears.
Four uncommon problems that can occur any time an ear is operated on include: (1) complete deafness in the operated ear, (2) permanent dizziness, (3) permanent facial paralysis on the side operated, and (4) persistent ringing or noise (tinnitus) in the ear operated. It is because of these risks that are beyond our control that we urge you to consider your surgery as seriously as we do.
Please be sure that you discuss the surgery with your physician so that he may answer, in detail, any question you may have.