A cochlear implant is an electronic device that partially restores hearing. It can be an option for people who have severe hearing loss from inner-ear damage and who receive limited benefit from hearing aids.
Unlike hearing aids — which amplify sound — a cochlear implant bypasses damaged portions of the ear to deliver sound signals to the auditory (hearing) nerve.
Cochlear implants use a sound processor that fits behind the ear. The processor captures sound signals and transmits them to a receiver implanted under the skin behind the ear. The receiver sends the signals to electrodes implanted in the snail-shaped inner ear (cochlea).
The signals stimulate the auditory nerve, which then directs them to the brain. The brain interprets those signals as sounds, though these sounds won't be just like normal hearing.
It takes time and training to learn to interpret the signals received from a cochlear implant. Within a year of use, most people with cochlear implants make considerable gains in understanding speech.
Cochlear implants can improve communication and quality of life for people with severe hearing loss who receive little benefit from hearing aids. Increasingly, cochlear implants in both ears (bilateral) are accepted as standard care for the treatment of severe hearing loss — particularly for infants and children who are learning to speak and to process language.
Adults and children who lost hearing after learning to speak can also benefit from cochlear implants. People who have cochlear implants report improved:
- Ability to hear speech without needing visual cues such as reading lips
- Recognition of normal, everyday environmental sounds
- Ability to listen in a noisy environment
- Ability to find where sounds are coming from
- Ability to hear television programs and telephone conversations
To be eligible for a cochlear implant, you must have:
- Hearing loss that is so severe it interrupts spoken communication
- Limited benefit from hearing aids as determined by specialized hearing tests
- No medical conditions or factors that increase the risks associated with cochlear implants
- High motivation to participate in rehabilitation sessions and to be part of the hearing world
- Clear understanding of what cochlear implants can and cannot do for hearing
Cochlear implantation surgery is generally safe. The risks include:
- Loss of residual hearing. Implantation of the device might damage any remaining ability to hear in that ear.
- Inflammation of the membranes surrounding the brain and spinal cord (meningitis) following cochlear-implant surgery in children. Vaccinations to prevent meningitis are generally given before implantation.
- Occasionally, surgery to repair or replace a faulty device.
Rarely, the risks can include:
- Facial paralysis
- Infection at the surgery site
- Balance problems
Cochlear implantation is done under general anesthesia, which means you or your child will be asleep during the procedure. You or your child might need to:
- Temporarily stop taking certain medications or supplements
- Avoid eating or drinking for a certain amount of time
Your doctor will give you specific instructions to help you prepare.
Before the procedure
You or your child will need a thorough medical evaluation to determine if cochlear implants are a good option. The evaluation is likely to include:
- Tests of hearing, speech and sometimes balance
- Physical examination to assess the health of the inner ear
- CT or MRI imaging of the skull to assess the condition of the cochlea and structure of the inner ear
- Sometimes, psychological testing to determine ability to learn to use cochlear implants
During the procedure
The surgeon will make an incision behind the ear, and form a slight depression in the portion of skull bone (mastoid) where the internal device rests.
The surgeon will then create a small hole in the cochlea and thread the electrode array of the internal device through this hole. The incision is stitched closed so that the internal device is under the skin.
After the procedure
You or your child might experience:
- Pressure or discomfort over the implanted ear or ears
- Dizziness or nausea
Most people feel well enough to return home the day of surgery or the day afterward. You will need to return to the doctor in about a week to have stitches removed.
The cochlear implants won't be turned on (activated) until two to six weeks after surgery — to give the surgery site time to heal.
To activate the cochlear implant, an audiologist will:
- Adjust the sound processor to fit you or your child
- Check the components of the cochlear implant to make sure they work
- Determine what sounds you or your child hears
- Give you information on the proper care and use of the device
Rehabilitation involves training the brain to understand sounds heard through the cochlear implant. Speech and everyday environmental noises will sound different from what you remember.
The brain needs time to recognize what these sounds mean. This process is ongoing and is best achieved by wearing the speech processor continuously during waking hours.
Results vary from person to person. Factors that can affect the outcomes of cochlear implantation include the age when hearing was lost and the length of time between hearing loss and cochlear implantation.
For children, the best results occur with implantation at a young age. Research also indicates that young children who have cochlear-implant surgery develop better hearing and speech than similar children with hearing aides.
For adults, the best results are associated with a shorter period of profound hearing loss before cochlear implantation. Adults with little or no experience of sound tend to benefit less from cochlear implants.