May 11, 2012
Dear Mayo Clinic:
I have had hearing aids for decades, but they haven't been very effective for the last year or so. My doctor recommends a cochlear implant and said I may have an even better result with one in each ear. Is it necessary to have two?
A cochlear implant may be a good next step if you have severe hearing loss and difficulty understanding speech even with hearing aids. It's important that you work with a specialist in hearing loss and hearing aids (audiologist) and/or a doctor who specializes in disorders of the ears, nose and throat (ENT) to evaluate your situation and needs.
After age 40, a person's hearing can start to decline. This is often due to inevitable changes that occur in the inner ear over time. Genetics and noise exposure can also contribute to hearing loss. After a certain point, hearing aids may no longer be effective for some people. When that happens, a cochlear implant may help a person hear much better.
A cochlear implant is a small electronic device for people who have severe hearing loss. The device bypasses the damage in the inner ear and allows many patients to hear well again. According to the U.S. Food and Drug Administration, approximately 219,000 people worldwide have cochlear implants. In the United States, roughly 43,000 adults and 28,000 children have the devices.
Unlike hearing aids, which amplify sounds, cochlear implants work by bypassing the damaged portions of the ear to stimulate the auditory nerve. Signals generated by the implant are sent by way of the auditory nerve to the brain, which recognizes the signals as sound.
A cochlear implant has outside and inside parts. The outside part, called a sound processor, is essentially a miniature computer. The inside part is an electrode array, which is inserted into the inner ear (cochlea) by an ENT surgeon. The operation generally takes from 1½ to 2 hours per implant and the device is surgically implanted under a general anesthetic. Patients are normally able to go home the same day or the day after surgery.
Patients considering cochlear implants should understand that hearing with an implant device is not exactly the same as normal hearing. Sounds that are conveyed through a cochlear implant have been described differently. Some people say it sounds like an electronic voice or like Mickey Mouse. The sounds differ from patient to patient.
Patients need time to learn how to hear with the implant. The time and the experience also differ among patients. Once patients become accustomed to the implant, they can usually hear and understand speech and environmental sounds. Newer devices and processing strategies (using different ways to stimulate the electrode that transforms speech to electrical stimuli) allow many patients to hear better in noisy environments and even swim with their cochlear implant.
Although most patients do fine with just one cochlear implant, bilateral implants (one for each ear) are becoming more common. The main benefit of bilateral implants is sound localization, which helps patients detect where a sound is coming from. For example, if someone behind you was talking, you would be able to detect that person's location more easily than if you had a cochlear implant in one ear only.
Bilateral implants also improve speech understanding in a variety of situations, including when background noise is present. Patients often say that the sound quality is better in stereo and is a big improvement compared to having just one cochlear implant.
— Sarah Oakley, Au.D., Audiology, Mayo Clinic, Scottsdale, Ariz.