Bilateral Cochlear Implants

Editor: The second half of Sunday's Plenary Session featured Dr. Douglas Backous discussing bilateral cochlear implants. Here's Chery'ls report.

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Douglas Backous, M.D. Medical Director, Dept. of Otolaryngology-Head and Neck Surgery, The Listen For Life Center, Virginia Mason Medical Center, Seattle

At the Sunday plenary session, Dr. Douglas Backous shared the results of studies on bilateral (two ears) cochlear implants.

Are two cochlear implants better than one? Controlled studies are being done in adults. Some are simultaneous, with both implant surgeries done on the same day, and others are sequential, with implant surgeries at different times. The studies are helping to show what, if any, benefits result from having two cochlear implants, and they are helping to identify surgical and programming challenges as well as potential risks.

Potential advantages of having two cochlear implants are:
1. Ability to locate the source of the sound
2. Improvement in understanding speech in a noisy setting
3. Ability to hear sounds on both sides of the head

Some of those participating in the study had surgery for both implants on the same day and activation on the same day. Others have sequential surgery at least 3 months apart and the first cochlear implant is activated before the second surgery.

FDA studies are now being done on the Nucleus 24 Contour and Med-El Combi 40. They are very controlled and are being closely watched. Those participating are 18 years or older, postlingually deaf, have bilateral severe to profound hearing loss, and less than 15 years of deafness prior to the surgery. Cochlear has 30 people done simultaneously and 2 sequentially. Med-El has 220 people worldwide, including 6 in the U.S. In Europe, some of the study participants were children.

Researchers have been looking for "squelch" advantages, where adding the second ear helps with central sound processing. These results are not yet clear because it involves the brain, which has to adapt.

Also being studied is the "head shadow" effect -- the ability to track a sound as it moves around -- and localizing, to pick up the differences in intensity and timing. Patients in the tests have been able to guess within 6-7 degrees where a sound is coming from.

Researchers found in the Med-El tests that using cochlear implants in both ears produced higher accuracy on sentences in noise than with one ear. The use of cochlear implants in two ears scored better in quiet as well.

A study by Dr. Bruce Ganz shows that we don't accurately predict the best ear for cochlear implantation, but two are giving better results than one.

Dr. Backous does not shave the head of patients having cochlear implant surgery. He uses tape to hold the hair back. He does surgery to place the cochlear implant on one side and then rolls the patient over to do the other side. He has dome two patients this way. One patient's surgery was completed in 2 hours and 20 minutes; the second patient's surgery was completed in 2 hours and 7 minutes.

Patients who have had two cochlear implants prefer two over one. No difference has been found in the rate of complications.

Q: Can someone previously implanted get a second implant of more recent technology, or would it have to be the same as the original? A: Right now researchers are trying to get patients with the same implant on both sides, but the door is open for experimenting.

Q: Has anyone studied the correlation between left-handed and right-handed preferences in picking the better ear for implanting? A: No data along these lines has been reviewed.

Q: Is there any study to compare the use of a cochlear implant in one ear and a hearing aid in the other? A: No study is being done now, but there is a good body of information now. A lot of patients are doing well with this arrangement, so there is no need to repeat it in a study. It is almost impossible to predict who will do well with a cochlear implant in one ear and a hearing aid in the other.

Q: Who will qualify for bilateral implants? A: The criteria would vary from ear to ear. Both ears would have to qualify. First we need to address reimbursement issues. People may have to pay for the second cochlear implant on their own.

Q: Is music better with a second cochlear implant? A: Most of the information we have is anecdotal. The jury is still out. Cochlear Corp. is putting together a processor that can drive two cochlear implants.

Q: With 300 bilateral implantations worldwide, have there been any failures? A: Yes. The information is now being evaluated and reviewed by the FDA. Some people are failing to do as well as they hoped with the second cochlear implant.

Q: What about using MRIs with cochlear implants? A: It depends on the MRI scanner and the device you use. The Nucleus cochlear implants allow you to remove the magnet with a small incision. MRIs of the head are the only concern, not the rest of the body.

-- Cheryl Heppner, Executive Director