If your child is 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, technology exists that can help people with profound hearing loss gain partial hearing—cochlear implants. Since the 1970s, cochlear implants have helped thousands of people detect sound and understand speech.
Hearing works like this: In the inner ear, the cochlea and auditory nerve which work together to turn acoustical sound waves that enter the ear into electrical impulses that are transmitted through the auditory nerve to the brain where they are perceived as sound. If any part of this complicated system is damaged, hearing loss occurs. A cochlear implant mimics this system, using electronic devices to go around the damaged areas. The 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.
How Cochlear Implants Work
Cochlear implants have helped individuals with severe and profound hearing loss hear for decades. It’s an amazing leap in technology, but just how does it work? A cochlear implant does more than amplify sound (like traditional hearing aids), it’s a complex system of electronics that bypasses damaged areas of the inner ear and sends electronic signals to the brain that can be interpreted as sound.
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 (you guessed it) behind the ear. Today’s body-worn processors are miniaturized and can be clipped to a shirt collar or ponytail. The style that’s best for your child depends on their activity level. Consult your audiologist for different wearing styles and options for young children.
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. How does the transmitter stay in place, you may wonder? Clips? Hair pins? Nope — magnets.
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. Let’s take a look at some of the internal components:
Remember how the transmitter stays on the skin using magnets? The magnet is part of the receiver coil 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.
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
Types of Cochlear Implants
While all cochlear implants use the basic process outlined above, 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. The electrode array sends each frequency is sent to a different area of the inner ear and the result is a more detailed, realistic type of sound.
It’s also good to know that 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.
A cochlear implant works like this:
- 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.
What Cochlear Implants Sounds Like
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. How helpful the device will be on your child is difficult to predict. Generally, success depends on a variety of factors, such as:
- 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 U.S. Food and Drug Administration has approved cochlear implants for infants as young as 12 months, 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.