Otosclerosis is a disease of the middle ear bones and sometimes the inner ear. Otosclerosis is a common cause of hearing impairment and is rarely hereditary.
The ear is divided into three parts; the external ear, the middle ear, and the inner ear. The external ear collects sound, the middle ear mechanism transforms the sound and the inner ear receives and transmits the sound.
Sound vibrations enter the ear canal and cause the eardrum to vibrate. Movements of the eardrum are transmitted across the middle ear to the inner ear fluids by three small ear bones. These middle ear bones (hammer or maleus, anvil or incus and stirrup or stapes) act as a transformer changing sound vibrations in air into fluid waves in the inner ear. The fluid waves stimulate delicate nerve endings in the hearing canals. Electrical impulses are transmitted on the nerve to the brain where they are interpreted as understandable sound.
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 hearing impairment occurs. If the trouble lies in the inner ear, a sensorineural or nerve hearing impairment is the result. When there is difficulty in both the middle and the inner ear a mixed or combined impairment exists. Mixed impairments are common in otosclerosis.
If we had been able to examine your middle ear under the microscope before a hearing impairment developed we could have seen minute areas of both softening and hardening of the bone. This process may spread to the stapes, the inner ear, or to both sides.
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 one it develops it may be permanent. On occasion the otosclerosis may spread to the balance canals and may cause episodes of unsteadiness.
Usually otosclerosis spreads to the stapes or stirrup none, the final link in the middle ear transformer chain. The stapes rests in the 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 audiometric examination (hearing tests).
There is no local treatment to the ear itself or any medication that will improve the hearing in persons with otosclerosis.
In some cases a nutritional supplement containing fluoride may be prescribed to slow or stop the loss of hearing. The supplement should not be taken by young children or pregnant women.
For patients who are not surgical candidates or do not wish to have surgery, a hearing aid or hearing aids may be an alternative. One may also consider other options such as a temporal bone implant (BAHA or Ponto).
The stapes operation (stapedectomy) is recommended for patients with otosclerosis who are candidates for surgery. This operation is usually performed under local anesthesia and requires but a short period of hospitalization and convalescence. Over 90 percent of these operations are successful in restoring the hearing permanently.
Stapedectomy or stapedotomy is performed though the ear canal under local or general anesthesia. A samll incision may be made behind the ear to remove muscle or fat tissue for use in the operation.
With the use of the operating microscope the eardrum is elevated and turned forward. The hearing bones are palpated and the diagnosis of otosclerosis of the stapes is confirmed. The laser is routinely used to vaporize parts of the stapes and the remainder of the stapes is removed with an instrument. A small opening is made in the footplate of the stapes. A stainless steel, titanium, or platinum piston (prosthesis or implant) is then placed into this opening and connected to the second hearing bone, or the incus. The eardrum is then returned to its normal position. While pistons in current use are safe with lower power MRI scanners (1.5 Tesla or less) only titanium, platinum, and plastic prostheses are compatible with MRI scanners of all strengths. You should ask your surgeon what material is to be implanted and keep this information for future reference.
The stapes prosthesis allows sound vibrations to pass from the eardrum to the inner ear fluids, correcting the conductive hearing loss. The hearing improvement obtained is usually permanent. Most stapes surgery patients may go home the same evening or the next morning. Most patients may return to work in seven days depending on the occupational requirements.
One should not plan to drive a car home from the hospital. Air travel is permissible three weeks following surgery. Automobile travel is usually permissible immediately.
The stapes operation can be performed on previously fenestrated ears, providing the hearing nerve function is essentially the same as necessary for an initial stapes operation. Seventy percent (70%) of these operations are successful in improving the hearing.
Hearing improvement may or may not be noticeable at surgery or immediately afterwards. If the hearing improves at the time of surgery it usually decreases 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 six 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 two percent (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 one percent, despite a perfect surgery, the hearing may be damaged that complete hearing loss may occur and 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 (tinnitus) may be more pronounced. Unsteadiness may persist for some time, but usually resolves with rehabilitation and medical therapy. Rarely, re-exploration may be necessary when hearing loss occurs, but time is usually given to allow the ear to heal completely.
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. Following successful stapedectomy, tinnitus is often decreased in proportion to the hearing improvement, but occasionally may be worse.
Dizziness is normal for a few hours following a 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 are not uncommon for a few weeks following surgery. In five percent of the patients this disturbance may persist.
A perforation (hole) in the eardrum membrane is an unusual complication of the surgery. It develops in less than one percent (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.
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 an implantable temporal bone implant.
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.