Cochlear implants and hearing aids are both used to help people who are hard of hearing. Hearing aids work by amplifying sound to help the ear hear better. Cochlear implants bypass the inner workings of the ear by sending signals directly to the auditory nerve.
Cochlear implants cannot cure deafness or provide true hearing. But for people who are severely hard of hearing or who are deaf, cochlear implants can supply some sense of sounds including warning signals and can help in understanding speech and other sounds.
What is a cochlear implant?
Cochlear implants consist of external parts that are worn on the head or upper body and internal parts that are surgically implanted.
These include a microphone, speech processor, and transmitter.
• The microphone picks up sounds and sends them to the speech processor. The microphone can be worn like a behind-the-ear hearing aid.
• The speech processor may be combined with the microphone in a behind-the-ear component, or may be housed in a small box that can be carried in a shirt pocket. The speech processor is a computer that takes the sounds from the microphone, analyzes them, and converts them to a digital signal.
• This signal is sent to the transmitter, which is worn on the head just behind the ear.
These include a receiver and electrodes, both of which are surgically implanted.
• The receiver is positioned under the skin just behind the ear and receives the digital signal sent by the transmitter that is worn on the head.
• The receiver sends the signal on to the electrodes which have been surgically inserted into the cochlea, which is a part of the inner ear. The electrodes pass on the electrical signal from the digital processor. This signal stimulates the fibers of the auditory nerve. This nerve carries the signals to the brain where they are interpreted as sound sensations.
Who can benefit from a cochlear implant?
Both children and adults can benefit from cochlear implants. Generally, patients of any age who receive the implants fit these criteria:
• Are deaf or severely hard of hearing
• Receive little or no benefit from hearing aids
• Have no other medical problems that make surgery risky
For adults, it’s also important that they have a strong desire to be part of the hearing world and to communicate through speaking and hearing.
Children as young as 14 months old have received cochlear implants. For children, it is also important that they, along with their parents, are involved as much as possible in the decision and consent process, understand what will be required of them to successfully use cochlear implants, have realistic expectations, and have support from their educational program.
In all cases, patients who receive cochlear implants require intensive rehabilitation from audiologists, speech-language pathologists, teachers, and counselors.
Patients will be taught how to use the implant and how to interpret the sounds they hear through it. For those who formerly were able to hear, the sounds perceived through the implant may seem unnatural at first. Those who have never heard must first be taught what the sounds are.
Research is also ongoing to see how cochlear implants could be used to help people with other types of hearing loss. Other studies are exploring ways to improve speech recognition through cochlear implants, as well as how cochlear implants may be able to help people whose hearing loss is limited to the higher frequencies.