Stapedectomy is a surgical procedure in which the innermost bone (stapes) of the three bones (the stapes, the incus, and the malleus) of the middle ear is removed, and replaced with a small plastic tube surrounding a short length of stainless steel wire (a prosthesis). The operation was first performed in the United States in 1956.
A stapedectomy is performed to improve the movement of sound to the inner ear. It is done to treat progressive hearing loss caused by otosclerosis, a condition in which spongy bone hardens around the base of the stapes. This condition fixes the stapes to the opening of the inner ear, so that the stapes no longer vibrates properly. Otosclerosis can also affect the malleus, the incus, and the bone that surrounds the inner ear. As a result, the transmission of sound to the inner ear is disrupted. Untreated otosclerosis eventually results in total deafness, usually in both ears.
Otosclerosis affects about 10% of the United States population. It is an autosomal dominant disorder with variable penetrance. These terms mean that a child having one parent with otosclerosis has a 50% chance of inheriting the gene for the disorder, but that not everyone who has the gene will develop otosclerosis. In addition, some researchers think that the onset of the disorder is triggered when a person who has the gene for otosclerosis is infected with the measles virus. This hypothesis is supported by the finding that the incidence of otosclerosis has been steadily declining in countries with widespread measles vaccination.
Otosclerosis develops most frequently in people between the ages of 10 and 30. In most cases, both ears are affected; however, about 10–15% of patients diagnosed with otosclerosis have loss of hearing in only one ear. The disorder affects women more frequently than men by a ratio of 2:1. Pregnancy is a risk factor for onset or worsening of otosclerosis.
With regard to race, Caucasian and Asian Americans are more likely to develop otosclerosis than African Americans.
A stapedectomy does not require any incisions on the outside of the body, as the entire procedure is performed through the ear canal. With the patient under local or general anesthesia, the surgeon opens the ear canal and folds the eardrum forward. Using an operating microscope, the surgeon is able to see the structures in detail, and evaluates the bones of hearing (ossicles) to confirm the diagnosis of otosclerosis.
Next, the surgeon separates the stapes from the incus; freed from the stapes, the incus and malleus bones can now move when pressed. A laser or small drill may be used to cut through the tendon and arch of the stapes bone, which is then removed from the middle ear.
The surgeon then opens the window that joins the middle ear to the inner ear and acts as the platform for the stapes bone. The surgeon directs the laser's beam at the window to make a tiny opening, and gently clips the prosthesis to the incus bone. A piece of tissue is taken from a small incision behind the ear lobe and used to help seal the hole in the window and around the prosthesis. The eardrum is then gently replaced and repaired, and held there by absorbable packing ointment or a gelatin sponge. The procedure usually takes about an hour and a half.
Good candidates for the surgery are those who have a fixed stapes from otosclerosis and a conductive hearing loss of at least 20 dB. Patients with a severe hearing loss might still benefit from a stapedectomy, if only to improve their hearing to the point where a hearing aid can be of help. The procedure can improve hearing in more than 90% of cases.
Diagnosis of otosclerosis is based on a combination of the patient's family history, the patient's symptoms, and the results of hearing tests. Some patients notice only a gradual loss of hearing, but others experience dizziness, tinnitus (a sensation of buzzing, ringing, or hissing in the ears), or balance problems. The hearing tests should be administered by an ear specialist (audiologist or otologist) rather than the patient's family doctor. The examiner will need to determine whether the patient's hearing loss is conductive (caused by a lesion or disorder in the ear canal or middle ear) or sensorineural (caused by a disorder of the inner ear or the 8th cranial nerve).
Two tests that are commonly used to distinguish conductive hearing loss from sensorineural are Rinne's test and Weber's test. In Rinne's test, the examiner holds the stem of a vibrating tuning fork first against the mastoid bone and then outside the ear canal. A person with normal hearing will hear the sound as louder when it is held near the outer ear; a person with conductive hearing loss will hear the tone as louder when the fork is touching the bone.
In Weber's test, the vibrating tuning fork is held on the midline of the forehead and the patient is asked to indicate the ear in which the sound seems louder. A person with conductive hearing loss on one side will hear the sound louder in the affected ear.
A computed tomography (CT) scan or x ray study of the head may also be done to determine whether the patient's hearing loss is conductive or sensorineural.
Patients are asked to notify the surgeon if they develop a cold or sore throat within a week of the scheduled surgery. The procedure should be postponed in order to minimize the risk of infection being carried from the upper respiratory tract to the ear.
Some surgeons prefer to use general anesthesia when performing a stapedectomy, although an increasing number are using local anesthesia. A sedative injection is given to the patient before surgery.
The patient is asked to have a friend or relative drive them home after the procedure. Antibiotics are given up to five days after surgery to prevent infection; packing and sutures are removed about a week after surgery.
It is important that the patient not put pressure on the ear for a few days after surgery. Blowing one's nose, lifting heavy objects, swimming underwater, descending rapidly in high-rise elevators, or taking an airplane flight should be avoided.
Right after surgery, the ear is usually quite sensitive, so the patient should avoid loud noises until the ear retrains itself to hear sounds properly.
It is extremely important that the patient avoid getting the ear wet until it has completely healed. Water in the ear could cause an infection; most seriously, water could enter the middle ear and cause an infection within the inner ear, which could then lead to a complete hearing loss. When taking a shower, and washing the hair, the patient should plug the ear with a cotton ball or lamb's wool ball, soaked in Vaseline. The surgeon should give specific instructions about when and how this can be done.
Usually, the patient may return to work and normal activities about a week after leaving the hospital, although if the patient's job involves heavy lifting, three weeks of home rest is recommend. Three days after surgery, the patient may fly in pressurized aircraft.
The most serious risk is an increased hearing loss, which occurs in about 1% of patients. Because of this risk, a stapedectomy is usually performed on only one ear at a time.
Less common complications include:
Severe dizziness or vertigo may be a signal that there has been an incomplete seal between the fluids of the middle and inner ear. If this is the case, the patient needs immediate bed rest, an examination by the ear surgeon, and (rarely) an operation to reopen the eardrum to check the prosthesis.
Most patients are slightly dizzy for the first day or two after surgery, and may have a slight headache. Hearing improves once the swelling subsides, the slight bleeding behind the ear drum dries up, and the packing is absorbed or removed, usually within two weeks. Hearing continues to get better over the next three months.
About 90% of patients will have markedly improved hearing following the procedure, while 8% experience only minor improvement. About half the patients who had tinnitus before surgery will experience significant relief within 6 weeks after the procedure.
Stapedectomy is a very safe procedure with a relatively low rate of complications. With regard to hearing, about 2% of patients may have additional hearing loss in the operated ear following a stapedectomy; fewer than 1% lose hearing completely in the operated ear. About 9% of patients experience disturbances in their sense of taste. Infection, damage to the eardrum, and facial nerve palsy are rare complications that occur in fewer than 0.1% of patients.
Alternatives to a stapedectomy include:
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American Academy of Audiology. 11730 Plaza America Drive, Suite 300, Reston, VA 20190. (703) 790-8466. http://www.audiology.org .
American Academy of Otolaryngology-Head and Neck Surgery, Inc. One Prince St., Alexandria VA 22314-3357. (703) 836-4444. http://www.entnet.org
Better Hearing Institute. 515 King Street, Suite 420, Alexandria, VA 22314. (703) 684-3391.
National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health. 31 Center Drive, MSC 2320. Bethesda, MD 20892-2320. http://www.nidcd.nih.gov .
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Carol A. Turkington Rebecca J. Frey, Ph.D.
Stapedectomies are usually done by otologists or otolaryngologists, who are surgeons with advanced training in treating ear disorders. A stapedectomy is usually performed as an outpatient procedure in an ambulatory surgery facility or same-day surgery clinic.