Recent advancements in cochlear implants

Dr Dillon D’souza, a Consultant ENT and Head and Neck surgeon attached to Jaslok hospital, Breach Candy Hospital and Desa’s Hospital, shares how the cochlear implants work and what recent technical advancements it has made in the recent times

Recent advances in cochlear implants

What is a cochlear implant?

A cochlear implant is an electronic device that takes over the work of the human ear and converts sounds to electrical signals that the brain understands as sounds. It delivers them to the brain via hearing nerve after fine-tuning the sound much like a graphic equaliser on a music system, through an electrode array surgically implanted into the inner ear.

Whom does it benefit?

People who have severe to profound hearing loss wherein, even after wearing hearing aids, the person will have difficulty in understanding normal speech even at loud volumes. While without hearing aids they could not even hear a loud noise.

How does one detect severe to the profound hearing loss in a child or adult?

The subject person could not hear the prime elements of a class discussion, including key context and content without the visual cues. They will have a smaller or limited vocabulary than their same age peers, not hear all the sounds in a word, commonly leaving off ‘s’, ‘ing’ and ‘ed’ in their speech and their writing, will have problems pronouncing some speech sounds, particularly those in the high frequency such as ‘s’ or ‘p’. They would feel tired at the end of sessions that required intense concentration or were conducted in noisy environments.

Very often, they misinterpret what is said although they ‘hear’ the speaker’s voice (they know that someone said something but couldn’t hear clearly enough to understand what was said.)

There is a limited understanding of colloquial languages, such as ‘pull up your socks’, in normal conversations, they have difficulty in understanding complex sentences, have poor vocal quality, have trouble explaining their ideas, and have limited background knowledge and experiences in the range of areas which can affect their learning and social skills.

Who is a candidate for a cochlear implant?

A person who has severe to profound hearing loss in both ears, has a functioning hearing nerve which is detected by medical tests, has lived at least a short while without hearing, has no medical reasons to avoid surgery, has no benefit from the best hearing aids, and has a good support group at home.

What are the components of a cochlear implant?

A cochlear implant consists of an external device that looks like a hearing aid, which has the function of capturing sound, tuning the sound like the graphic equaliser on a music system, using software, and then transmitting the sound like a radio station to the surgically implanted device.

The surgically implanted part consists of an antenna, like a radio antenna, which picks the sound from the external device. A processor which is like a music system output takes the sound and sends it to different parts of the electrode which is implanted In the inner ear, much like a surround sound music system delivers sounds to different speakers in a room.

The electrode array, which is like Diwali lights, depending on the processor, different lights at different points switch off and on. In this case, different electrodes switch off and on causing different parts of the hearing nerve ends to receive stimulation that the brain perceives as a sound of different frequencies.

What has changed in cochlear implants since they were introduced in India since 1987?

External device: It has become smaller and lightweight, added microphones to pick up a sound and better software with faster processors to process more sound and give clearer and focused sound to the patient. Also, it has become smarter, able to send and receive data from the implanted device to diagnose problems and improve the efficiency of sound transmission to the brain.

Implanted device: It has become smaller and lightweight, electronically smarter, wherein the implanted device can send diagnostic information back to the external device. Also, it occupies less space and requires less surgical exposure.

The electrode array has more electrodes and is slimmer and less damaging to the inner ear structures resulting in more information delivered to the hearing nerve while preserving residual hearing, which has resulted in better speech and sound understanding even in noisy environments.

Also, the materials used have advanced to a stage where the body rarely rejects the implant.

Surgery: It has become more precise and less invasive, resulting in quicker healing and shorter hospital stays for the patient.

Sound processing software: It has advanced and is still advancing. Post-surgery, it enables the doctors to fine-tune the patients hearing and create software environments wherein even in noisy environments, speech and sound understanding are getting even better. It has resulted in less speech and sound training required post-surgery and more natural sound hearing.

Cost factor: Both surgery and implantation costs are decreasing as devices are being mass produced, and surgical techniques less invasive which reduce the surgery time and less hospital stay.