What is a cochlear implant?
A cochlear implant is an implanted electronic hearing device that produces useful hearing sensations to a person with severe to profound nerve deafness by electrically stimulating nerves inside the inner ear. The implanted device is controlled by an external processor that is typically worn on the ear. These two portions are connected by magnets, one under the skin and one above the skin.
Who is a good candidate for cochlear implants?
Cochlear implants help adults and children with severe to profound hearing loss or those who get little or no benefit from hearing aids.
What is normal hearing?
Your ear consists of three parts that play a vital role in hearing — the external ear, middle ear and inner ear.
Conductive hearing: Sound travels along the ear canal of the external ear, causing the ear drum to vibrate. Three small bones of the middle ear conduct this vibration from the eardrum to the cochlea (auditory chamber) of the inner ear.
Sensorineural hearing: When the three small bones move, they start waves of fluid in the cochlea. These waves stimulate more than 16,000 delicate hearing cells (hair cells). As the hair cells move, they generate an electrical current in the auditory nerve. The electrical signal travels through interconnections in the brain to specific areas of the brain that recognize it as sound.
How is hearing impaired?
If you have disease or obstruction in your external or middle ear, your conductive hearing may be impaired. It can possibly be corrected through medical or surgical treatment. An inner ear problem, however, can result in a sensorineural impairment, or nerve deafness. In most cases, the hair cells are damaged and do not function. Although many auditory nerve fibers may be intact and can transmit electrical impulses to the brain, these nerve fibers are unresponsive because of hair cell damage. Since severe sensorineural hearing loss cannot be corrected with medicine, it can be treated only with a cochlear implant.
How do cochlear implants work?
Cochlear implants bypass damaged hair cells and convert speech and environmental sounds into electrical signals and send these signals to the hearing nerve.
A cochlear implant has two main components:
- An internal component is a small electronic device surgically implanted under the skin behind the ear and connected to electrodes inserted inside the cochlea.
- An external component is usually worn behind the ear and has a speech processor, microphone and battery compartment. The microphone captures sound, allowing the speech processor to translate the sound into distinctive electrical signals. The signals, or “codes,” travel up a thin cable to the headpiece and are transmitted across the skin via radio waves to the implanted electrodes in the cochlea. The electrodes’ signals stimulate the auditory nerve fibers to send information to the brain, where it is interpreted as meaningful sound.
Cochlear implant benefits
Cochlear implants are designed only for individuals who receive little, if any, benefit from a hearing aid. They must be 12 months of age or older (unless childhood meningitis is responsible for deafness).
Many otolaryngologists (ENT specialists) perform implant surgery. Your primary doctor can refer you to an implant clinic for an evaluation. The implant team (otolaryngologist, audiologist, nurse and others) will determine your candidacy for a cochlear implant and review the appropriate expectations of the cochlear implant. The implant team will also conduct a series of tests including:
- Ear (otologic) evaluation: The otolaryngologist examines the middle and inner ear to ensure that no active infection or other abnormality precludes the implant surgery.
- Hearing (audiologic) evaluation: The audiologist performs extensive hearing tests to find out how much you can hear with and without a hearing aid.
- X-ray (radiographic) evaluation: Special X-rays are taken, usually computerized tomography (CT) or magnetic resonance imaging (MRI) scans, to evaluate your inner ear anatomy.
- Physical examination: Your otolaryngologist also performs a physical examination to identify any potential problems with the use of general anesthesia needed for the implant procedure.
Cochlear implant surgery
Cochlear implant surgery is usually performed as an outpatient procedure under general anesthesia. An incision is made behind the ear to open the mastoid bone leading to the middle-ear space. Once the middle-ear space is exposed, an opening is made in the cochlea and the implant electrodes are inserted. The electronic device at the base of the electrode array is then placed behind the ear under the skin.
Is there care and training after the operation?
Several weeks after surgery, your cochlear implant team places the signal processor, microphone and implant transmitter outside your ear and adjusts them. They teach you how to look after the system and how to listen to sound through the implant. There are many causes of hearing loss, and some patients may take longer to fit and require more training based on their unique needs. Your team will ask you to come back to the clinic for regular checkups and readjustment of the speech processor as needed.
What can I expect from an implant?
Most adult cochlear implant patients notice an immediate improvement in their communication skills. Children require time to benefit from their cochlear implants as the brain needs to learn to correctly interpret the electrical sound input. While cochlear implants do not restore normal hearing, and benefits vary from one individual to another, most users find that cochlear implants help them communicate better through improved lip-reading. Also, 90% of adult cochlear implant patients can discriminate speech without the use of visual cues. There are many factors that contribute to the degree of benefit a user receives from a cochlear implant, including:
- How long a person has been deaf.
- The number of surviving auditory nerve fibers.
- A patient’s motivation to learn to hear.
Your team will explain what you can reasonably expect from your cochlear implant. It is rare that patients do not benefit from a cochlear implant, but it may take time before full benefit is reached.
FDA approval for implants
The U.S. Food and Drug Administration (FDA) regulates cochlear implant devices for both adults and children and approves them only after thorough clinical investigation. Be sure to ask your otolaryngologist for written information, including brochures provided by the implant manufacturers. You need to be fully informed about the benefits and risks of cochlear implants, including how much is known about safety, reliability and effectiveness of a device; how often you must come back to the clinic for checkups; and whether your insurance company pays for the procedure.
Costs of implants
More expensive than a hearing aid, the total cost of a cochlear implant including evaluation, surgery, the device and rehabilitation can cost as much as $100,000. Fortunately, most insurance companies and Medicare provide benefits that cover the cost.
For more information about cochlear implants, please call Pediatrix ENT of Orlando at 407-253-1000.