Otosclerosis and Stapes Surgery
Otosclerosis is an inherited disease that affects the bone of the ear. The name "otosclerosis" means "scarring of the ear", which accurately describes what happens in affected ears. The inner ear (organ of hearing and balance) is surrounded by the strongest bone in the body, known as the "otic capsule". In people with otosclerosis, a part of this bone begins to grow and scar, a process that evolves over many years.
In the early stages of the disease, areas of soft bone appear around the inner ear. This process is termed “otospongiosis”, and can result in bone loss from the otic capsule. With time, the bone loss stops, and the soft areas scar. This hard, scarred bone is called “otosclerosis”.
As the bone around the ear changes with otosclerosis, problems may result in the function of the ear. This most commonly occurs when the bone of the otic capsule grows onto the stapes (or "stirrup") bone. The stapes usually passes sound vibrations to the inner ear by moving in and out against the fluid of the inner ear. If the bone from the otosclerosis grows onto the stapes, the stapes movement may be limited or stopped altogether, leading to hearing loss. This is the most common type of hearing loss seen in otosclerosis. It known as a "conductive" or “mechanical” hearing loss, since the disease keeps sound vibrations from being conducted through the middle ear to the inner ear.
The abnormal bone from otosclerosis may also injure the inner ear directly by growing against the organs of hearing or balance. Individuals with otosclerosis will often have a combination of both a "conductive" as well as a inner ear hearing loss.
Otosclerosis often runs in families, and over half of people affected will have someone in their family with similar symptoms. Not everyone with the “otosclerosis gene” will have symptoms from it. It occurs more commonly in families of certain ethnic groups (it is more common in individuals of northern European or Indian descent, and is seen less frequently in individuals of Asian or African descent). The exact cause of the disease remains unknown.
What are the Symptoms?
The hearing loss from otosclerosis is usually progressive over many years. Both ears are often affected, although one ear is usually worse than the other. The hearing loss may progress during pregnancy and (possibly) with certain types of hormonal treatment.
Tinnitus (Ear Noises)
Tinnitus is the presence of abnormal ear and head noises, and can result from otosclerosis. The injury from otosclerosis may result in “ringing”, “rushing”, or other sensations. This is from nerve impulses generated despite the lack of any sound coming into the ear. Such noises will often improve after surgery or with the use of a hearing aid.
Individuals with inner ear injury from otosclerosis may also have balance disturbances. The bony lesions can surround the balance canals and alter the sensation of motion. However, this rarely becomes a significant problem.
What are the Tests for Otosclerosis?
Hearing tests are essential in diagnosing otosclerosis. There are specific patterns of hearing loss that are suggestive of this process. Hearing tests are also used to monitor progression of disease, and to assess treatment results.
Radiologic studies, especially high resolution CT scanning, are occasionally used to confirm the diagnosis of otosclerosis.
What is the Treatment for Otosclerosis?
There are several ways to manage otosclerosis. Treatment options are selected on a number of factors and should be customized to each affected individual. The options are discussed briefly below:
Watchful waiting -- You do not have to do anything about otosclerosis. This is not the type of disease that requires that something be done soon to prevent progression, and there is no "cure" that gets rid of the underlying bone growth in the inner ear. Many people are not particularly troubled by their symptoms, and so may elect to wait, and obtain a hearing test every so often to see if the problem is progressing.
Medicines -- Unfortunately, there is no medicine that can reverse the effects of otosclerosis. In some people who have progressive inner ear injury, fluoride treatment may be of help in preventing the progression of symptoms. Fluoride may strengthen the inner ear bone similar to the way it can strengthen teeth. It does not, however, help with the "conductive" hearing loss caused be stapes immobility.
For fluoride to be effective, it must be taken daily over a prolonged period of time. Fluoride likely works by converting active, bone-destroying “otospongiosis” lesions to less active “otosclerosis” scar. The side effects of fluoride therapy are few, and taking the medication with meals can minimize any stomach upset. Since fluoride is readily incorporated into growing teeth and bones, the large doses given should usually be avoided in children and pregnant women.
Hearing Aids -- The great majority of individuals with otosclerosis can do quite well with hearing aids. Most people with the disease have a "conductive" hearing loss from a problem with mobility of the stapes bone. In most cases, the inner ear works quite well. This means that if a hearing aid can be used to increase the level of the sound vibrations, enough sound can usually get to the inner ear, and the inner ear can make appropriate use of the information. Hearing aids are not for everyone, but they can usually be tried safely to see if they are a benefit.
Surgery -- Surgery can be a highly effective treatment for otosclerosis. The procedure is called a "stapedectomy" (or "stapedotomy"). The procedure is intended to "bypass" the fixed part of the stapes bone by removing it, and replacing it with a new, mobile, prosthetic bone. In the procedure, all or part of the stapes bone is removed with either a laser or micro-drill. A tiny “piston” is then placed between the second bone of hearing (the incus) and the inner ear. Occasionally, additional tissue is taken from the external ear to help seal the opening into the inner ear.
Patients undergoing otosclerosis surgery usually go home the same day of surgery. The operation takes about 1 to 2 hours, and most patients are able to resume normal activity after about 1 week. It usually takes 4-6 weeks for the ear to fully heal, and for the hearing to improve.
Surgery can only help the "conductive" part of the hearing loss (that from immobility of the stapes bone). Surgery cannot help inner ear hearing loss.
What are the Risks of Stapes Surgery?
As with any surgical procedure, there are some risks associated with surgery for otosclerosis. These should be discussed in more detail with your doctor.
Hearing improvement occurs in about 90% of patients. In about 8%, the hearing remains unchanged or the inner ear becomes slightly worse, and a hearing aid can still be used. In about 1 to 2%, the hearing loss can become worse. Rarely (about 1 in 100) the inner ear will stop working altogether, meaning that a hearing aid can no longer be used. In some cases, additional surgery may be necessary.
Dizziness can occur after surgery for otosclerosis. This is usually mild, and improves in the first few days to weeks. In some very rare cases, dizziness can be more severe or prolonged, and may require additional surgery.
Inner ear noise, or “tinnitus”, is usually improved following otosclerosis surgery. However, there are cases when tinnitus can be left unchanged or even become worse. This is particularly in ears in which the hearing has decreased.
There is a small nerve behind the eardrum (the chorda tympani) that supplies taste to one side of the tongue. This nerve can be stretched or injured during surgery. In this case, there can be some loss of taste sensation, or a “metallic” taste on the tongue usually lasting 3 to 6 months.
In less than 1% of cases, a hole can develop in the eardrum following surgery. This will often heal with time on its own, and rarely requires an additional procedure.
Weakness of the Face
A very rare complication of stapedectomy is weakness of the face due to swelling of the facial nerve. If this occurs, the chances are excellent that the facial function will return with time and medical therapy.