Cochlear implants
A cochlear implant is an electronic device that improves hearing in people who have severe hearing loss due to damage of the inner ear.
Overview
A cochlear implant is an electronic device that improves hearing. It can be an option for people who have severe hearing loss from inner-ear damage who are not able to hear well with hearing aids.
Unlike hearing aids, which amplify sound, a cochlear implant bypasses damaged portions of the ear to deliver sound signals to the hearing (auditory) nerve.
Cochlear implants use a sound processor that fits behind the ear. The processor captures sound signals and sends 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 the signals to the brain. The brain interprets those signals as sounds, though these sounds won't be just like natural hearing.
It takes time and training to learn to interpret the signals received from a cochlear implant. Within 3 to 6 months of use, most people with cochlear implants make considerable gains in understanding speech.
A cochlear implant uses a sound processor that's worn behind the ear. A transmitter sends sound signals to a receiver and stimulator implanted under the skin. They stimulate the auditory nerve with electrodes that have been threaded into the cochlea. Some types of cochlear implants have one outside unit that has a speech processor, microphone and transmitter combined (lower left). Others have these as separate outside parts (upper left and on right).
Why it's done
Cochlear implants can improve hearing in people with severe hearing loss who are no longer helped by using hearing aids. Cochlear implants can improve their communication and quality of life.
Cochlear implants may be placed in one ear (unilateral) or both ears (bilateral). Adults will often have one cochlear implant and one hearing aid at first. Adults may then progress to two cochlear implants as the hearing loss advances in the hearing aid ear. Cochlear implants are often placed in both ears at the same time in children with bilateral severe hearing loss — particularly for infants and children who are learning to speak and process language.
Adults of any age and children who are as young as 6 to 12 months old can 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 everyday environmental sounds
- Ability to listen in a noisy environment
- Ability to find where sounds are coming from
- Ability to hear television programs, music and telephone conversations
- Symptoms of ringing or buzzing (tinnitus) in the implanted ear
To be eligible for a cochlear implant, you must have:
- Hearing loss that interrupts spoken communication
- Limited benefit from hearing aids as determined by specialized hearing tests
- Motivation to participate in hearing rehabilitation and be part of the hearing world
- Realistic expectations of what cochlear implants can and can't do for hearing
Risks
Predicted outcomes
Cochlear implant surgery is very safe.
Risks of cochlear implantation can include:
- Loss of residual hearing. In some people, implantation of the device can cause a loss of any remaining, unclear, natural hearing in the implanted ear.
- Inflammation of the membranes surrounding the brain and spinal cord (meningitis). Meningitis can occur after cochlear implant surgery. Vaccinations to reduce the risk of meningitis are generally given to adults and children before implantation. The risk of this very rare complication is less frequent than 1 in 1,000 people with cochlear implants.
- Failure of device. Surgery may sometimes be needed to repair or replace a faulty internal device. This occurs in less than 5% of people over many years.
Complications are rare and can include:
- Bleeding
- Facial paralysis
- Infection at the surgery site
- Device infection
- Balance problems
- Dizziness
- Taste problems
- New or worsened ear noise (tinnitus)
- Spinal fluid leak
How you prepare
Cochlear implant surgery is done under general anesthesia. This means you or your child will be in a sleep-like state during the procedure. Instructions before surgery may include:
- Stop taking certain medications or supplements for a certain amount of time
- Avoid eating or drinking for a certain amount of time
Your surgeon will give you specific instructions to help you prepare.
What you can expect
Before the procedure
You or your child will need a detailed medical evaluation to determine if cochlear implants are a good option. Health care providers will conduct an evaluation that may include:
- Tests of hearing, speech and sometimes balance
- Physical exam to assess health and anatomy
- MRI or CT imaging tests of the skull to assess the condition of the cochlea and inner ear structure
You'll work with an audiologist — a health care professional trained in evaluating and rehabilitating hearing loss and related issues — and your surgeon to determine which cochlear implant type is best for your needs. All cochlear implants include both internal and external parts. Options include:
- An internal cochlear implant that has an external unit that attaches to the side of the head. The external unit combines a speech processor, microphone and transmitter in one device. It can be charged when needed.
- An internal cochlear implant with an external sound processor that fits behind the ear. The transmitter attaches to the side of the head.
Developing a totally implanted system with no external unit is being investigated.
During the procedure
Your surgeon will make a small cut (incision) behind your ear, and form a small hole in the portion of skull bone (mastoid) where the internal device rests.
Your surgeon will then create a small opening in the cochlea in order to thread the electrode of the internal device. The skin incision is stitched closed so that the internal device is under your skin.
After the procedure
For a short time, you or your child might experience:
- Pressure or discomfort over the ear that has the device implanted
- Dizziness or nausea
Most people feel well enough to return home the day of surgery.
An audiologist will turn on the device.
Activation
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
- Set the device so that you can hear to the best of your ability
Rehabilitation
Rehabilitation involves training your brain to understand sounds heard through the cochlear implant. Speech and everyday environmental noises will sound different from what you remember.
Your 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.
Regular, lifelong follow-up visits to check and program the device and to do auditory testing can help you get the most benefit from your cochlear implants.
One type of cochlear implant has an external unit that attaches to the side of your head (scalp) behind your ear and combines a speech processor, microphone and transmitter in one device. It can be charged when needed.
Results
The results of cochlear implant surgery 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 the cochlear implant surgery.
For children, the best results generally occur with getting a cochlear implant at a young age if they are born with significant hearing loss.
For adults, the best results are generally associated with a shorter period of profound hearing loss before cochlear implantation. Adults with little or no experience with sound tend to benefit less from cochlear implants, although both groups of adults generally improve after cochlear implantation.
Some predicted outcomes may include:
- Clearer hearing. Many people who meet the hearing criteria for cochlear implantation may eventually get clearer hearing with using the device.
- Improved tinnitus. Although ear noise (tinnitus) isn't a primary reason to receive a cochlear implant, the cochlear implant may partially suppress or improve the severity of tinnitus during use. It can rarely worsen tinnitus severity.