Cochlear Implant

Cochlear implants are electronic devices that, once implanted, improve the hearing ability in those with severe hearing problems. It is helpful in those people in whom the hearing difficulty is due to inner ear damage (cochlea).

How does cochlear implants work?

A cochlear implant works by converting sounds into electrical signals that stimulate the auditory nerve. The nerve carries these signals to the hearing center in the brain, creating a sense of sound. 

A cochlear implant has two parts:

1. Outer part
2. Inner part

The outer part remains outside the body and looks like hearing aid. The inner part of the cochlear implant will be inside the body. The surgeon will insert a magnet inside the scalp, which holds these parts together. 

The outer part consists of a microphone and speech processor. The microphone receives and amplifies the sound in the environment. The speech processor process this sound arranges them and converts into digital signals.

The inner part consists of a transmitter with a receiver-stimulator package and electrode array. The transmitter receives the digital signals processed by the speech processor and converts them into electric signals. The electrode transmits this electric signals to different parts of the auditory (hearing) nerve.

The auditory nerve then carries these impulses into the brain to create the sense of hearing. All these things happen so fast that a person can hear sounds without any delay.

Cochlear implant versus hearing aids:

Hearing aids increase the volume of sound, thereby increases the chance of affected nerve picking them up. A cochlear implant creates a new path for the sound, thereby bypassing the affected inner ear and transmitting it directly to the hearing nerve. It is the best option for those with hearing loss due to damage to the cochlea.

Who can have cochlear implants?

It is for those who have severe to profound sensorineural hearing loss. The loss should be due to the impaired function of cochlea and not due to problems in the nerve. A cochlear implant cannot function if there is any pathology in the nerve.

Anyone (child or adult) with severe hearing loss can be a candidate for cochlear implantation. 

What is the age criteria for cochlear implants?

A child as young as six months is a candidate for Cochlear implantation. The ideal time is before the child is 18 months of age. As it is before speech development, the improvement in hearing and speech is better.

Pre-operative procedure

The patient undergoes a series of tests to confirm the degree and cause of hearing loss and to rule out other pathologies that might contradict the surgery. These include

• Pure tone audiometry (hearing test)
• Oto-acoustic emissions (to determine the function of the cochlea)
• BERA (to determine the function of the nerve)
• MRI- Brain with inner ear
• Psychological assessment
• Pediatric assessment

Children will need to receive the pneumococcal and Hemophilus influenza vaccine before the procedure.

Cochlear implantation team

There is a team of specialists who will be part of the cochlear implant procedure. It includes 

• ENT surgeon
• Audiologist
• Speech and language pathologist
• Pediatrician
• Anesthetist
• Psychologist

Cochlear implantation procedure

The cochlear implantation procedure in complete entails two steps.

The first step is the surgical procedure for implanting the inner part. The second step is an outpatient procedure called switch-on. The outer part gets connected during this procedure. The surgeon will also program the implant setting as per the individual needs.

During surgery, the surgeon will make a small incision behind the ear and drill the mastoid bone to reach the inner ear. After that, they will place the receiver-stimulator package in the periosteal pouch, and the electrode array inside the cochlea.

The patient has to stay for at least two days in the hospital. 

Recovery from cochlear implant surgery

Being a minor surgery, you will be able to go back home the same day or after. You will have to take proper care of the surgical wound by keeping it clean and dry. Bathing your head will have to wait for two or three days. 

You should not bend your head or lift anything heavy. While lying down, you will have to use a pillow to keep your head elevated. Avoid strenuous activities for a week or so. You can go back to your routine activities after that. 

Risks and complications of cochlear implant surgery

Cochlear implant surgery is a safe one with very few risks and complications. Some of the possible risks are

• Reactions to anesthesia
• Bleeding during surgery
• Infections of the surgical wound
• Damage to the facial nerve
• Change in taste 
• Problems with balance
• Having tinnitus, a ringing sensation in the ears
• Risk of meningitis
• Difficulty in having procedures like MRI scans

Switch-on procedure:

The switch-on procedure is done 3-4 weeks after surgery. During this, the surgeon will connect the outer part and program the implant as per the need.

Auditory Rehabilitation:

The most important process is the auditory rehabilitation. It involves training the patient to hear sounds. As per this, the team will make minor adjustments in the program settings of the implant. The aim is to make it function at an optimal level and help you have the best of it.

Post-lingual children and adults might need 2-3 months of rehabilitation. The pre-lingual children need it for at least six months to 1 year.

Advantages of cochlear implant

The main benefits of cochlear implants are

• You can hear soft sounds like footsteps and moderate sounds like closing of the doors
• You will not have to rely on lip-reading to understand speech
• It is possible to watch TV and listen to music like others
• You can talk freely over a telephone

Besides these, a cochlear implant will make you more comfortable socially. You will feel more self-confident by being able to make conversations with others.

Disadvantages of cochlear implant

There are some disadvantages to cochlear implants as well. These include

• You will lose all of your natural hearing ability by having the implants
• In some persons, the implants fail to improve hearing
• If the implant fails, you will need another surgery
• The cost of the implants are high
• Contact sports, physical trauma, falls, etc. can damage the implants
• You will have to remove the outer part while bathing, swimming, etc
• You may hear some strange noises with the implant.

Precautions with cochlear implant

There are a few things that you should be careful about while having cochlear implants. Some of them are

• If you have MRI scans, you need to tell the doctor about the implants. The magnetic field of the MRI can damage the implant and also cause you pain and discomfort.
• You will need special precautions while having radiation treatments for cancers of the head and neck.
• Avoid blows or falls that can damage the implant. 
• Children playing contact sports like football, basketball, etc. will have to wear protective gear to avoid damage to the implant.
• Be careful while bathing and swimming as water can damage the external part. Remove it before getting exposed to water.
• Do not go too near to TVs and plastic toys as the static electricity they create can damage the implant.
• Do not keep your mobile phone close to the ear. Use earphones while using mobiles.
• You may activate metal detectors and security alarms as you pass through these. So keep a record of having the implant in you to avoid trouble.

Success rate of cochlear implants

Cochlear implant surgery is a hugely successful one with a failure rate of less than one percent. The hearing ability usually gets better with time. You will need some training to help you get the best results. If you have it at a younger age, the better will be the outcome