Audiology

Cochlear implants

Manufacturers

Cochlear implants are devices which are surgically implanted in the ear to stimulate the auditory (hearing) nerve. These are especially useful for persons who have severe/profound sensori-neural hearing impairments and traditional hearing aids do not provide adequate benefit.

Although the use of cochlear implant does not result in ‘normal hearing’, it enables the individual to hear most environmental sounds and speech at comfortable loudness levels. It improves speech reading (lip reading) and helps in speech production and monitoring.

Both adults and children who were born without hearing or who lost their hearing later in life are reported to benefit from the cochlear implants. The criteria in deciding on use of a cochlear implant include:

• Severe/profound sensori-neural hearing loss in both ears

• age 2 years or older (more recently children younger than 2 years have also been implanted)

• little or no benefit in understanding speech through hearing aids or a vibrotactile device

• no contra-indications to implant surgery or post implant training

• a high degree of motivation and appropriate expectations

• for children, an educational setting that emphasizes development of auditory skills

An external microphone which looks like a behind-the-ear hearing aid is worn over the ear. The sounds picked up by the microphone are coded by a speech processor which is worn on the body of the user, and sent to the transmitting coil placed behind the ear. The coil transmits these coded signals to the receiver implanted below the skin. The receiver stimulates the electrode array which extends into the cochlea and stimulates the auditory nerve. The signals from the auditory nerve are interpreted as sounds.

Post surgical programming of the speech processor and training and follow-up visits are necessary for obtaining optimum benefits.