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March 17, 2006

Cochlear Devices for Sensorineural Hearing Loss

From: - Charlotte,NC,USA - Mar 17, 2006

Hearing and Hearing Loss When we hear, sound is funneled into the outer part of the ear through the ear canal. The sound waves cause the eardrum at the end of the ear canal to vibrate. The vibrations are carried to three small bones attached to the other side of the eardrum (the area called the middle ear). The bones move and carry the vibrations to a fluid-filled, snail-shaped chamber in the inner ear called the cochlea. The movement of the fluid stimulates tiny fibers, or hair cells, inside the cochlea. Movement of the hair cells sends an electrical current to the hearing nerve (the auditory nerve), then on to the brain. The brain translates the information into recognizable sound.

According to the National Institute on Deafness and Other Communication Disorders, about 17 out of every 1,000 children in the U.S. have hearing loss. About two to three of every 1,000 children are born deaf. Each year, about 4,000 Americans experience sudden deafness.

There are three main types of hearing loss. Conductive hearing loss occurs when sounds are unable to get through the outer ear to the eardrum or bones in the middle ear. An example is wax build-up in the ear canal that impedes the passage of sound waves. Sensorineural hearing loss occurs when the hearing structures in the cochlea or nerve pathways to the brain are damaged. It can be caused by disease, tumor, aging, or exposure to loud noises or certain drugs. Sensorineural hearing loss is permanent. Mixed hearing loss is a combination of problems associated with conductive and sensorineural hearing loss.

Cochlear Devices for Sensorineural Hearing Loss A cochlear device is an implant used to bypass damaged hair cells in the cochlea. Unlike a hearing aid, which simply amplifies sound, the cochlear implant converts sounds into electrical signals and sends those signals directly to the auditory nerve.

Several components make up the cochlear implant. A microphone picks up sounds. A speech processor selects and shapes the sounds and sends them in the form of electrical signals to a receiver. The receiver is the part of the device implanted under the skin behind the ear. The electrical impulses travel through a thin wire to tiny electrodes implanted in the cochlea. The signals directly stimulate the auditory nerve fibers to send the sound information to the brain.

According to the Cochlear Implant Association, Inc., more than 20,000 people in the U.S. have received a cochlear implant - over 8,000 of them are children. Cost of the implant (including testing, surgery and the components) is about $30,000 to $50,000. In almost all cases, it's covered by insurance or government health plans.

Cochlear Implants for Children Hearing loss has profound effects on children, causing a significant delay in development of oral and written language skills. Researchers say currently, 85 percent of newborns are tested for hearing loss within a day of birth. Early intervention (including use of hearing aids, when appropriate) significantly improves language acquisition, speech intelligibility, academic achievement and social skills development.

At Johns Hopkins University, researchers believe the earlier the intervention, the better. Currently, doctors recommend cochlear implants be placed in children between six months and one year. It appears there is a very critical time in an infant's development for hearing and brain training. With later implantation, children miss some of that important development. Research shows that children who receive the devices before they turn three have significantly better word recognition and speech understanding than those who receive the implants after six.

For information on hearing loss or cochlear implants: Alexander Graham Bell Association for the Deaf and Hard of Hearing, American Academy of Otolaryngology, Cochlear Implant Association, Inc., National Institute on Deafness and Other Communication Disorders,

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