Cochlear implant: what it is and how it works

In case of profound deafness, when the hearing aid is not sufficient to compensate for hearing loss, a cochlear implant is used.

The implant is, in fact, a very sophisticated electronic device that replaces the functioning of the cochlea, the organ of the inner ear responsible for transmitting sound to the brain. When deafness is severe, the activity of the cochlea is severely impaired, and therefore the cochlear implant can replace its function.

How is the cochlear implant made?

The external part consists of a processor, a microphone, and a battery, housed in a sort of behind-the-ear hearing aid and connected via a thin cable to the circular transmitting antenna.

The internal part contains a receiver and some electrodes, in variable numbers, depending on the model of the system. The internal part is completely under the skin and is connected to the transmitting antenna through a magnet, to allow you to easily remove the implant.

How does it work?

1. The processor, positioned behind the ear, captures sounds and transforms them into digital signals. The processor is powered by a battery contained in the lower part.

2. Through a thin cable, the processor transmits the signals to the circular antenna, connected by a magnet to the internal part.

3. The internal part of the system receives the signals from the antenna and transmits them into the auger by means of a cable equipped with electrodes.

4. The electrodes send the impulses to the acoustic nerve and reach the brain, which interprets them as an auditory sensation. Each electrode processes a different frequency for a complete understanding of each sound.

What is the difference between the hearing aid and cochlear implant?

The hearing aid, through amplification, stimulates the still functioning nerve cells of the inner ear and therefore makes the best use of the residual nerve structures of the ear.

The cochlear implant instead replaces the damaged cochlear functionality. It converts acoustic signals into electrical signals, which, going beyond the compromised structures of the inner ear, directly stimulate the acoustic nerve.

Who is the cochlear implant for?

To people, adults or children, born or become deaf with age, with a profound or total hearing loss in both ears. Earlier intervention is always essential. Small children and adults who have recently become deaf are the ideal subjects. However, not all deaf people are suitable for implantation.

It is not recommended for adults who have never used the ear canal such as deaf adults from birth who use sign language.

Who can benefit from a cochlear implant? 

These electronic devices are designed to improve the quality of life of those affected by severe hearing loss or deafness, especially if both ears (bilateral hearing loss), and especially if very young children, still at the age in which they are processing the language ability (prelingual deafness). Furthermore, cochlear implants are suitable for those - both adults and children - who have lost hearing after learning the language. In all these cases the device applied inside the inner ear allows, or can allow, the following acquisitions:

- Ability to hear a speech without needing to read the speaker's lips

- Ability to recognize sounds from the surrounding environment

- Ability to locate individual sounds even in a rowdy environment

- Ability to trace the origin of a sound

- Ability to follow television programs and conduct a telephone conversation

But let’s see the identikit of the ideal candidate to enter the list for a cochlear implant:

- Who has a hearing loss so severe as to compromise the use of the word

- Who has had little or no benefit from common hearing aids as evidenced by specific hearing tests

- Those who are in good health and do not present other risk factors such that the implantation of an electronic device inside the ear could be dangerous.

- Who shows a strong motivation to recover hearing and to undergo the rehabilitation sessions necessary to become familiar with the implant

- Who understood how a cochlear implant works and what can be expected after surgery

Cochlear implants are NOT indicated, because they would be completely useless, for those affected by deafness resulting from irreversible damage to the auditory nerves.

Risks

As for any other surgery, even the one necessary for the application of a cochlear implant involves minimal risks, which the patient, before being subjected to it, is well aware of it. Specifically, here are the main dangers and negative consequences that, albeit remotely, can occur and invalidate the success of the intervention:

- Residual hearing loss caused precisely by implantation of the device

- Meningitis in children, a very rare but still possible consequence of implantation, which can cause inflammation of the membranes surrounding the spinal cord and brain (meninges). This danger can be eliminated by subjecting children to vaccination against meningitis in advance.

- Failure to apply the implant, which may require a second surgery

If these are the main threats, there are other very remote ones, which in any case the doctor-surgeon is required to indicate and explain to his patients waiting to undergo this operation:

- Facial paralysis

- Infection in the surgery area

- Balance disorders

What are the benefits of cochlear implants?

For people with implants:

  - Auditory ranges vary from almost normal ability to understand speech to no auditory benefit.

  - Adults often have immediate benefits and continue to improve for approximately three months after the initial set-up sessions. Then, although performance continues to improve, improvements are slower. The performance of IC users can continue to improve for several years.

 - Children can improve at a slower pace. Much post-implantation training is needed to help the child use the new hearing he is now experiencing.

  - Most people with IC perceive loud, medium, and soft sounds. People report that they can hear different types of sounds, such as the sound of footsteps, the slamming of doors, engine sounds, phone ringer, barking of dogs, the whistle of the kettle, the rustling of leaves, the sound of a light switch, the power on and off, and so on.

  - Many understand speech without lip-reading. However, even if this is not possible, using the implant helps the lip reading.

  - Many can make phone calls and understand familiar voices on the phone. Some are proficient in normal telephone use and may even understand an unknown speaker. However, not all people who have IC are able to use the phone.

  - Many can follow TV more easily, especially when you can even see the speaker's face. Listening to the radio, however, is often more difficult as there are no visual clues available.

 - Some can enjoy music. Some appreciate the sound of some instruments (piano or guitar, for example) and certain voices. Others don't smell well enough to enjoy music.

Author: Vicki Lezama