What is Otosclerosis?
Otosclerosis is a condition in which new and unwanted bony tissue is formed in the bone which surrounds the inner ear. This new bone contains many blood vessels and is rather less hard than normal bone. Gradually the new bone matures and becomes hard (sclerotic). Less than 1% of the population is affected by this condition. Deafness is the main symptom and is usually present in both ears. Most patients notice the deafness before the age of 50. Noises in the ear (tinnitus) are present in most cases. A few patients may have some slight unsteadiness but this is rarely severe. Pain and discharge from the ears are not features of otosclerosis.
How does Otosclerosis occur?
Normal hearing is the result of sound waves in the outer ear being converted to nerve signals to the brain. The sound energy vibrates the ear drum. The drum vibrates three little bones in the middle ear which conduct the sound to the inner ear. These little bones are called the malleus, incus and stapes. It is the stapes which connect to the inner ear in a bony gap called the oval window. In otosclerosis the formation of new bone around the oval window stops the stapes from moving. This produces the deafness. In normal hearing it is movement of the stapes which stimulates the nerve endings in the inner ear to produce signals which go to the brain. In a small number of cases the new bone also interferes with the function of the inner ear (cochlea). This inner ear damage also produces deafness.
Why does Otosclerosis occur?
The cause of otosclerosis is unknown. Pregnancy sometimes makes the hearing worse in otosclerosis. It is for this reason that the condition is thought to be sometimes related to hormone levels. Otosclerosis tends to run in families. For these reasons it is thought that there is a hereditary or genetic basis for the disorder.
Treatment involved for Otosclerosis
Usually a hearing aid can be used with good effect. A hearing aid will be prescribed for those who are either too young or too old for surgery. There can be other reasons for not operating, such as poor health. Children are not usually offered surgery because they are more liable to frequent ear infections and may have congenital abnormalities of the ear, which make the operation less successful. The operation should never be done on the only ear with useful hearing. Infection of the outer ear is also a reason to avoid surgery. The operation which is done for otosclerosis is called a stapedectomy .
STAPEDECTOMY is usually done under general anaesthetic. It is performed using an operating microscope and the approach is through the ear canal. The ear drum is lifted out of its groove with an attached flap of skin. The middle ear can then be examined and the diagnosis confirmed visually. The purpose of the operation is to replace the fixed stapes bone with a substitute which can move. Usually, part of the fixed base and the stapes is removed, and an artificial bone replacement is put into position. The "prosthesis" may be made of non-reactive plastic or other material. Usually one end is hooked over the incus and the other is placed in the opening in the stapes foot plate.
Possible complications
The manipulation of the stapes always produces a reaction in the inner ear. This shows itself as a degree of giddiness and possibly hearing loss. In 90% of cases the results of stapedectomy are very good. In a small percentage of cases there may be severe or total loss of hearing in the operated ear. This may occur immediately after surgery or be delayed for several years. For this reason it is usual not to operate on the second ear without a gap of several years. In about 10% of cases the hearing is only slightly improved or there is no improvement. The facial nerve which supplies the muscles of the face runs through the middle ear. This nerve is occasionally damaged, producing a lop-sided weakness of the face. Another nerve called the chorda tympani supplies the sense of taste. This nerve is frequently damaged. This results in a temporary metallic taste which does not usually cause any significant problem. Giddiness with loss of hearing and tinnitus may occur some time after surgery. This may be due to a leakage of fluid around the artificial stapes. This condition is called a perilymph leak and requires a further operation on the ear. Infections of the middle ear are very rare after stapes surgery but are treated very promptly when they do occur.
After Treatment
Immediately after surgery you will feel unsteady through varying degrees. Pain is not a problem after stapedectomy. Movement of the head will make you feel giddy. During the first day, patients are nursed in bed and moving of the head discouraged. Drugs are given by injection to prevent giddiness. You will be warned not to blow the nose. From the second day, you will be slowly mobilized and the injections are usually changed to treatment by mouth. On the third day, and provided you are not unduly unsteady, you may be discharged home. Usually the ear canal dressing is removed before leaving hospital. Sometimes ear drops or antibiotics may be prescribed. After surgery you will be seen as an outpatient. In some cases stitches may have been placed in the ear and these need to be removed. Hearing improvement is not measured until at least 3 weeks after surgery. Most patients are able to return to work in the third or fourth week. If you get severe pain, discharge or marked unsteadiness after leaving hospital, you should report the problem to the surgeon or his staff. The surgeon will want to follow up the result of stapedectomy at intervals for several years. You are advised to avoid pressure changes wherever possible. This means not swimming deeply underwater or diving. Flying should be avoided when you have a cold.
Stapedetomy - The surgical Procedure
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