Otosclerosis is a common cause of hearing impairment and may be inherited. Someone in earlier generation of your family may have had the condition and passed it down to you. Similarly, your descendants may inherit this tendency from you, although the hearing impairment may not manifest itself for a generation or two.
Function of the normal ear:
The ear is divided into three parts: an external ear, a middle ear and an inner ear. Each part performs an important function in the process of hearing. The external ear consists of the auricle and ear canal. These structures gather the sound and direct it toward the eardrum membrane. The middle ear chamber lies between the external and the inner ear and consist of an eardrum membrane and the three small ear bones (ossicles): malleus (hammer), incus (anvil) and stapes (stirrup).
These structures transmit sound vibrations to the inner ear. In so doing they act as a transformer, converting sound vibrations in the external ear canal into fluid waves in the inner ear. The inner ear chamber contains the microscopic hearing nerve endings bathed in fluid. Fluid waves stimulate the delicate nerve end, which in turn transmit sound energy to the brain where it is interpreted.
Types of hearing impairment:
The external ear and the middle ear conduct and transform sound; the inner ear receives it. Where there is some difficulty in the external or middle ear, a conductive hearing impairment occurs. When the trouble lies in the inner ear, a sensorineural or nerve hearing impairment is the result. Difficulty in both the middle and inner ear results in a mixed impairment.
HEARING IMPAIRMENT FROM OTOSCLEROSIS
Had we been able to examine your inner ear under a microscope before a hearing impairment developed, we would have seen under a microscope before a hearing impairment developed, we would have seen minute areas of both softening and hardening of the bone. This process may spread ot 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 functioning of the cochlea. This “nerve type” 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 occassion, the otosclerosis spreads to the balance canals of the inner ear and may cause episodes of unsteadiness.
Usually ocosclerosis spreaads to the stapes or stirrup bone, preventing movement of 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.
By performing specific hearing tests, the amount of hearing loss due to involvement of the stapes, and the degree of nerve impairment present can be determined.
TREATMENT OF OTOSCLEROSIS
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 may be helpful in preventing further loss of hearing.
The stapes operation (stapedectomy or stapedotomy) is recommended in patients with conductive hearing loss caused by “stapedial” otosclerosis. This operation is performed under local or general anesthesia. It is performed as outpatient surgery or may require a short period of hospitalization. Over 90% of these operations are successful in improving hearing.
Following examination the physician will offer one of the following as your recommendation/predicted outcome:
1. You have a minor degree of conductive hearing loss caused by stapedial otosclerosis. As such, we do not advise surgery at this time.
2. You have stapedial otosclerosis with a significant conductive hearing loss. If the stapes operation is successful, you will have improved hearing from the involved side. If the otosclerosis involves both ears, a stapedectomy on the other ear can be performed 6 to 9 months later.
3. You have good hearing nerve function and are a very suitable candidate for the stapes operation.
4. Your hearing nerve has deteriorated slightly. If the stapes operation is successful, serviceable hearing will be restored to you.
5. Your hearing nerve has deteriorated to some extent. If the stapes operation is successful, you should be able to hear in many situations without an aid, but may need an aid for distant hearing.
6. Your hearing nerve has deteriorated considerably. If the stapes operation is successful, you will gain more benefit from the use of a hearing aid.
7. Your hearing nerve has deteriorated severely. For this reason, the chances of surgery improving your hearing are reduced. If surgery should prove successful, your hearing should be improved to the extent that you may be able to use a hearing aid.
8. Your hearing loss is due to inner ear and nerve involvement. As such, surgery would not be of benefit to you at this time. Many of the operations performed today were not available a few years ago. Through ear research, we hope to be able to help sensorineural (nerve) hearig impairment in the future.
THE STAPES OPERATION (STAPEDECTOMY)
Stapedectomy is performed through the ear canal under local or general anesthesia. At times, an incision may be made above the ear to remove muscle tissue for use in the operation.
Under high power 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 a laser. A stapes prosthesis is inserted to replace the diseased stapes. The ear drum membrane is then folded back to its normal position.
The stapes prosthesis allows sound vibrations to again pass from the eardrum membrane to the inner ear fluids. The hearing improvement obtained is usually permanent.
The patient may return to work in three days depending upon occupational requirements. Patients having to fly in for their surgery should plan on staying in (the local area) for a total of two-three days including the day of surgery.
One should not plan to drive a car home from the hospital. Air travel is permissible 48-72 hours following surgery.
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 fluids accumulating in the middle ear. Improvement in hearing may be apparent within 3 weeks of surgery. Maximum hearing, however, is obtained in approximately 3 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 good chance of success.
In 2% of the cases, the hearing may be further impaired due to the development of scar tissue, infection, blood vessel 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 an aid in that ear. For this reason, the poorer hearing ear is usually selected for surgery.
Most patient 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 or injury of the delicate nerve endings in the inner ear. Since the nerve carries sound, this irritation or injury is manifested as ringing, roaring or buzzing. It is usually worse when the patient is fatigued, nervous or in a quiet environment.
RISKS AND COMPLICATIONS OF STAPEDECTOMY
Dizziness is normal for a few hours following stapedectomy and may 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 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) 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 can heal spontaneously. If healing does not occur, surgical repair may be required.
Weakness of the Face
A very rare complication of stapedectomy is weakness of the face due to facial nerve injury. This may occur as the result of an abnormality or swelling of the facial nerve. The resulting facial weakness is usually a temporary condition.
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”. However, even patients with severe to profound hearing impairment from otosclerosis can benefit from a very strong hearing aid or a cochlear implant. In the older patient, the hearing loss due to the otosclerotic process is less likely to progress.
If you decide NOT to have surgery performed at this time or if surgery is not advisable, you should have periodic examinations, especially if the ear is draining. Untreated chronic ear disease may result in serious complications. Should you develop dull pain in or about the ear, increased discharge, dizziness, or weakness of the face, you should immediately contact us.