How is a cochlear implant different from a hearing aid?
Hearing aids amplify sound and send it through the auditory system. For some people with severe and profound sensorineural hearing loss, the inner ear is significantly damaged, and doesn’t effectively send sound information to the brain. For these people, hearing aids are of limited benefit. Cochlear implants bypass the damaged inner ear, and directly stimulate the hearing nerve. Hearing aids are worn externally on the ear or in the ear canal, while cochlear implants have both external parts as well as surgically implanted internal components. Hearing aids are worn by people with mild, moderate, severe and profound hearing loss. Cochlear implants are for people with bilateral severe to profound hearing loss. Neither hearing aids nor cochlear implants “cure” hearing loss or deafness, or restore hearing to normal. Both can help people to hear better, and can improve quality of life for the people who wear them and their families.
Hearing aids deliver wonderful, clear sound through the “normal” auditory pathway. But hearing aids rely on the cochlea (inner ear) to transmit sound to the auditory nerve and on to the brain. Sometimes the sensory cells in the cochlea are simply not able to transmit clear sound; instead the cochlea adds distortion so that words are not clear. Words may sound garbled and render speech unintelligible to the listener. A cochlear implant candidate can often hear when someone is talking, but they cannot distinguish the talker’s words. A cochlear implant can be thought of as a cochlear bypass. It replaces the function of the sensory cells in the cochlea and sends auditory information up the auditory pathway beyond the distortions of the cochlea. Auditory nerve fibers are directly stimulated by electrodes implanted into the cochlea.
Cochlear implants differ from hearing aids in two important ways. First, hearing aids simply make sounds louder. A cochlear implant transforms speech and environmental sounds into electrical information, which in turn stimulates the auditory nerve structures that provide information to the brain. Second, unlike a removable hearing aid, a cochlear implant is inserted via a surgical procedure. Who is a candidate for a cochlear implant? Ages 12 to 24 months: • Profound bilateral sensorineural hearing loss (SNHL). • No medical contraindications. • Lack of progress in the development of auditory skills. • High motivation and appropriate expectations from family. • Ages 25 months to 17 years: • Bilateral severe to profound sensorineural hearing loss (SNHL). • Thirty percent or less understanding of words in the best aided condition. • Lack of progress in the development of auditory skills. • No medical contraindications. • High motivation and expectations. Ages 18 years or older: • Bilateral
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