If your child has a severe or profound hearing loss in both ears, traditional hearing aids may not be enough to provide adequate sound perception and comprehension for speech understanding. Fortunately, cochlear implants can help people with profound hearing loss gain access to sound. Since the 1970s, cochlear implants have helped thousands of people detect sound and understand speech.
What is a Cochlear Implant?
One of the biggest ways cochlear implants differ from traditional hearing aids is that part of the system is surgically implanted into the inner ear. The external components include a speech processor and a transmitter. The implanted, internal components include a receiver coil and an electrode array.
Speech Processors
There are two styles of speech processors: behind-the-ear (BTE) and body-worn.
BTE processors look similar to a hearing aid and are worn behind the ear. Body-worn processors are typically worn on or off the ear.
The style that’s best for your child depends on his or her activity level. Consult your audiologist to discuss the current options available for young children.
Transmitter
The sounds have been processed and coded. Now, it’s time to get them to the brain using the transmitter. The transmitter sits on top of the skin and sends code to the internal parts of the cochlear implant. It is held in place with magnets.
Receiver Coil
The magnets that keep the transmitter in place on the skin’s surface are attracted to the receiver coil technology that is surgically placed under the skin behind the ear. The receiver coil has another important function: It takes code from the transmitter and turns it into electronic signals that the brain can interpret.
Electrode Array
The electronic signals are prepped and ready to go. Now, electrical contacts, known collectively as an electrode array, act like messengers to get the signals from the receiver coil to the brain. The electrode array makes tiny, highly accurate, electrical pulses on the hearing nerve fibers that connect the inner ear and the brain. The brain recognizes these electric pulses as sound.
How do Cochlear Implants work?
While sound is received by the ear, it is actually heard in the brain. To understand how cochlear implants work, we need to understand how typical hearing works.
Hearing is a complex process that involves many parts of the ear working together to convert sound waves into information that is sent to the brain where that sound is interpreted and understood. This video provides a good overview of how the hearing system works.
The outer ear, middle ear, inner ear and auditory centers of the brain all make up the auditory system.
Here’s how it works:
- The outer ear collects sound waves moving through the air and directs them to the eardrum.
- The eardrum vibrates with sound.
- Sound vibrations move from the eardrum through the ossicles (bones in the middle ear) to the cochlea.
- Sound vibrations cause the fluid and tiny hair cells inside the cochlea to move.
- Hair cell movement creates neural signals, which are picked up by the auditory (hearing) nerve.
- The auditory nerve sends signals to the auditory areas (or hearing centers) of the brain, where they are interpreted as sounds and speech.
The different parts of the ear and rest of the auditory pathway act as stations, reacting to and moving sound to the next station in the hearing system. A cochlear implant mimics this system.
The electronic device(s) bypasses any damaged areas and sends electronic signals to the brain that can be interpreted as sound. As a result, people who use cochlear implants may have increased sound awareness, better environmental sound recognition, enhanced speechreading abilities, improved speech production and the ability to understanding speech without speechreading.
The Process of Hearing with Cochlear Implants
- Sound is received by the microphone.
- Electrical pulses that represent the energy contained in sound signals are sent from the microphone to the speech processor.
- The speech processor selects and codes the most useful portions of the sound signals.
- Code is sent to the transmitter.
- Transmitter sends code across skin to receiver/stimulator.
- Receiver/stimulator converts code to electrical signals.
- Electrical signals are sent to electrode array in the cochlea to stimulate hearing nerve fibers.
- Signals are recognized as sounds by the brain.
Are all Cochlear Implants the same?
While all cochlear implants function using the same basic process, the quality of the sound they produce can vary, just like the sound system in your car or living room. There are three components in particular that have the biggest impact: the microphone, the speech processor and the electrode array.
There are three cochlear implant systems approved for sale in the United States by the U.S. Food and Drug Administration (FDA): Advanced Bionics, Cochlear Americas and MED-EL Corporation.
Is a Cochlear Implant right for my child?
Your cochlear implant team will conduct tests and evaluations (called a pre-cochlear implant evaluation) before making a final recommendation for your child. The evaluation process is designed to accomplish the following:
- Determine whether the child’s hearing loss is significant enough to warrant a cochlear implant
- Provide the family with information about technology, surgery and required follow-up
- Reveal whether there are any medical reasons why the child should not have the surgery
- Determine what educational supports are required or need adaptation
- Assess the child’s current communication skills and learning style
The FDA provides a comprehensive list of the benefits and risks of cochlear implants.
Are Cochlear Implants always successful?
Cochlear implants do a great job at helping individuals with severe and profound hearing loss, but even the best cochlear implants do not provide typical hearing. Your child’s results are difficult to predict.
Generally, success depends on a variety of factors including:
- Age at the time of implant
- Auditory memory for sound and speech
- Length of deafness
- Primary mode of communication
- Educational setting
- Length of time the implant is used
- Quality of the equipment
Research suggests that implantation works best for young children, ideally, before age three. The FDA has approved cochlear implantation for infants as young as 9 months of age, although children who are even younger have received the devices.
The quality of the equipment also has an impact on the quality of sound, just like the sound system in your car or living room. Although cochlear implant recipients have a wide range in performance, the benefits for most users include improved speech recognition, enhanced speech production skills, ability to perceive speech without speechreading and improved sound awareness and recognition. Today, advances in implant technology enable more children to maximize these benefits and develop listening and spoken language skills.
