What Is Cochlear Implant and How It Works?

Cochlear implant restores useful hearing in people in whom the organ of hearing in the inner ear has not developed or is destroyed by disease or injury. It bypasses the damaged hair cells and directly stimulates the spiral ganglion nerve fibres.

The spiral ganglion nerve fibres of auditory nerve provide information to the hearing centres in the brain through direct stimulation of the hearing nerve. Cochlear Implant contains surgically implanted and external components.

About one in 1,000 babies born in our country is profoundly deaf. So, considering the nearly 40,000 births every day, the number of deaf people in India would be incredibly high. Treatment options for these individuals are hearing aids and cochlear implant surgery.

Hearing aids are not very costly and would benefit individuals with hearing loss of severe degree (to some extent). When hearing aids fail, the only treatment option is cochlear implant surgery.

How Does Normal Hearing Work?

In order to understand how a cochlear implant works, it is helpful to have a basic understanding of how normal hearing operates:

1. The outer ear collects sound waves as they pass through the air and sends them down the ear canal.

2. The sound waves cause the eardrum and the three tiny ear bones to vibrate. This vibration is passed down the chain of the ear bones to the cochlea.

3. The vibration causes the tiny little hair cells in the cochlea to move, which in turn send electrical signals to the hearing nerve.

4. The signal travels up the hearing nerve to the brain where it is interpreted as sound.

What is Cochlear Implant

Surgically Implanted Components:

• Receiver or stimulator in a case, which is surgically implanted under the skin behind the ear, and contains a magnet, that couples in the transmitter worn externally.

• Electrode array is inserted into the cochlea.

Externally Worn Components:

• Microphone

• Speech processor that can be worn on the body or behind the ear.

• Transmitting coil, a small disk about the size of a one-rupee coin, which sticks to the skin behind the ear via a magnet, and is connected to the microphone by a small cable.

How It Works:

1. Speech processor converts sound waves into digital code.

2. The code is transmitted through the coil to the implant under the skin.

3. Digital codes are then converted to electrical signals and sent along the electrode array.

4. Electrodes stimulate the cochlea’s hearing nerve fibres, which relay the sound signals to the brain to produce hearing sensations.

Candidates for Cochlear Implants:

• People who suffer from severe to profound hearing loss in both ears. Recently, this has been changed to – from moderate to profound hearing loss in both ears.

• People with limited or no benefit from hearing aids.

• People with no other medical conditions that could make surgery risky.

• People with a strong desire to be part of the hearing world or those who have the support of a motivated family.

The Process:

Tests are done to determine whether a person is a suitable candidate for the implant:

• Audiologic testing
• Psychological testing
• Medical examination
• CT Scan and MRI

Commit to Care:

Counseling is also done to ensure that the candidate would benefit from the implant and have the motivation to participate in the process.

It is important for the person to understand what cochlear implant will and will not do. Also, they should be committed to care for the implant.

Following the tests and counseling, the surgery is done. Sometimes an overnight stay in the hospital is required or it may be done on an outpatient basis.

Also Read: Ear Cancer Causes, Symptoms and Treatment

Learning to Listen:

Couple of weeks after the surgery, the person has to return to fit the external parts, and to activate and program the implant by an audiologist.

The fitting process is done within a few days but additional visits are required to activate, adjust, and program the implanted electrodes. Also, as the individual learns to use the implant, re-programming may be required.

Audiologists, speech-language pathologists and counselors, provide extensive rehabilitation services as these individuals learn to handle communication.

• They are taught how to use the implant.
• How to respond to the sounds they are receiving.
• For people who could hear before, sounds through the implant may seem different.
• Others who have never heard, must be taught about sounds.

SOURCE: B-Positive Health Magazine

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