WHAT IS A COCHLEAR IMPLANT?
A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or severely hard-of-hearing. The implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin. An implant system has two parts:
- The external processor consists of a microphone, which picks up sound from the environment and a microcomputer, which selects and codes sounds picked up by the microphone.
- The internal device, the implant, consists of a transmitter and receiver/stimulator, which receive signals from the speech processor and convert them into electric impulses and an electrode array, which is a group of electrodes that collects the impulses from the stimulator and sends them to different regions of the auditory nerve.
An implant does not restore normal hearing. Instead, it can give a deaf or hard of hearing person a useful representation of sounds in the environment and help him or her to understand speech as well as be an aid to speechreading.
How does a cochlear implant work?
A cochlear implant is very different from a hearing aid. Hearing aids amplify sounds so they may be detected by damaged ears. Cochlear implants bypass damaged portions of the ear and directly stimulate the auditory nerve. Signals generated by the implant are sent by way of the auditory (hearing) nerve to the brain, which recognizes the signals as sound. Hearing through a cochlear implant is different from normal hearing and takes time to learn or relearn. However, it allows many people to recognize warning signals, understand other sounds in the environment, and enjoy a conversation in person or for some users, by telephone.
Who gets cochlear implants?
Children and adults who are deaf or severely hard-of-hearing may be candidates for cochlear implants. According to the Food and Drug Administration (FDA), through June 2010, more than 219,000 people worldwide had received implants. In the United States, roughly 42,600 adults and 28,400 children have received them.
Adults who have lost all or most of their hearing often can benefit from cochlear implants. They learn to associate the signal provided by an implant with sounds they remember. This often provides recipients with the ability to understand speech solely by listening through the implant, without requiring any visual cues such as those provided by lipreading or sign language. Post-implantation aural rehabilitation may be necessary for the patient to receive the optimum benefit from the cochlear implant. Every person is different as are their results with a cochlear implant.
Cochlear implants, coupled with intensive post-implantation therapy, can help young children to acquire speech, language, and social skills. Most children who receive implants are between two and six years old, but older children can be candidates as well. Individual history plays a large role in the success of an individual with a cochlear implant. Early implantation provides exposure to sounds that can be helpful during the critical period when children learn speech and language skills. In 2000, the FDA lowered the age of eligibility to 12 months for one type of cochlear implant.
How does someone receive a cochlear implant?
To be considered for a cochlear implant, the patient will need to undergo a cochlear implant evaluation by a cochlear implant audiologist as well as a medical evaluation by the cochlear implant surgeon. This process usually takes 2-3 hours and any interested family members are encouraged to attend. The patient will be tested with his or her hearing aids on as well as without the hearing aids. The different cochlear implant manufacturer’s devices will be explained with a hands on counseling session. Realistic expectations and limitation of cochlear implants and any other appropriate options will be discussed. You will see the surgeon to discuss the surgery, possible risks and complications as well as outcomes. If you do decide to pursue a cochlear implant, you will need to have an MRI or CT of your head to determine if you are a cochlear implant candidate.
Use of a cochlear implant requires both a surgical procedure and significant therapy to learn or relearn the sense of hearing. Not everyone performs at the same level with this device. The decision to receive an implant should involve discussions with medical specialists, including an experienced cochlear-implant surgeon. The process can be expensive. For example, a person’s health insurance may cover the expense, but not always. Some individuals may choose not to have a cochlear implant for a variety of personal reasons. Surgical implantations are almost always safe, although complications are a risk factor, just as with any kind of surgery. An additional consideration is learning to interpret the sounds created by an implant. This process takes time and practice. Audiologists are involved in this learning process, and you may be referred to a Speech-language or an auditory-verbal therapist for aural rehabilitation. Prior to implantation, all of these factors need to be considered.
What does the future hold for cochlear implants?
With advancements in technology and continued follow-up studies with people who already have received implants, researchers are evaluating how cochlear implants might be used for other types of hearing loss.
NIDCD is supporting research to improve upon the benefits provided by cochlear implants. Research is currently be conducted looking at using a shortened electrode array, inserted into the beginning of the cochlea, for individuals whose hearing loss is limited to the higher frequencies. There are studies which explore ways to make a cochlear implant convey the sounds of speech more clearly. Other studies are looking at improving music appreciation for patients with a cochlear implant or a totally implantable cochlear implant. Bilateral cochlear implantation or bi-modal implantation (wearing a hearing aid on one ear and a cochlear implant on the other), is one topic that has much research supporting the use of both ears. This research has made insurance companies, surgeons, audiologists, teachers for the hard of hearing, rethink past beliefs, advancing the potential for individuals with hearing loss.