A cochlear implant is an electronic medical device that is surgically implanted and that acts as a replacement to the damaged cochlea. This surgery restores the ability to perceive sounds and speech and is done only on persons suffering from severe to profound hearing loss, in cases where hearing aids failed to give any benefit. A cochlear implant is the best option for people with severe to profound sensorineural hearing loss, that is when there is damage to the sensory cells in the inner ear.
Cochlear implants are tiny devices that work differently from hearing aids. Unlike the latter, cochlear implants provide a sense of sound by directly stimulating the auditory nerve, rather than amplifying sound signals. They, however, are neither the replacements of the natural God-gifted ear nor can they completely cure a hearing-impaired person. This technology only helps the deaf or hard of hearing persons perceive the sound sensation by bypassing the damaged parts of the inner ear.
A cochlear implant involves two parts - external and internal. The external components include a microphone, a speech processor and a transmitter. The microphone picks up the sound signals, the speech processor analyzes and digitizes them and sends them to the transmitter that is worn on the head just behind the ear. It then sends the signals to the internal receiver.
The internal part of a cochlear implant includes a receiver and one or more electrode arrays. The receiver is located just under the skin on the temporal bone, which collects the sound signals from the transmitter and converts them to electrical pulses, and dispatches them to the electrodes that have been surgically inserted in the inner ear. These electrodes directly stimulate the auditory nerve fibres and the brain then interprets these signals as sound.
Nowadays, cochlear implant candidates can include both adults and children, depending on the type and degree of hearing loss in a person. Even children as young as 12 months are eligible for cochlear implants.
The eligibility criteria for children to undergo cochlear implants are -
- Have profound hearing loss in both the ears.
- Have had little or no benefit from hearing aids.
- Age appropriate cognitive development.
- No risks involved during surgery due to medical issues.
- They understand (when able), along with their parents, their role in the successful use of cochlear implants.
- Are willing (if able), along with their parents, to undergo the surgery.
- Have full support from the educational institution or program that would help them in developing their auditory and language skills.
The eligibility criteria for adults to undergo cochlear implants are -
- Have severe or profound hearing loss in both the ears.
- Hearing aids do not benefit them much.
- Do not have any medical problems that might put the person at risk during the surgery.
- Strongly want to be a part of the hearing and communication world.
However, studies say that the adults who have lost their hearing after learning speech and language, have greater chances of their cochlear implant being successful than those who have lost hearing before learning speech and language.
The process to determine the candidacy for Cochlear Implant includes a medical examination, auditory assessment, and sometimes a psychological evaluation. However, the Cochlear Implant team must obtain all the information first, and try to provide reliable answers to two key questions:
(1) Is a cochlear implant the only way out?
(2) Are there any medical restrictions that may risk the surgery?
As the saying goes, “with great power comes great responsibility”; to perform a sensitive surgery like a cochlear implant, a responsible and skilled teamwork is required. A responsible team of cochlear implant includes -
- ENT (Ear, Nose and Throat) Consultant or Surgeon - responsible for medical evaluation, surgery and post-operative care
- Audiologist - does a hearing evaluation, sound processor programming and fitting (mapping).
- Speech Language Pathologist - does speech and language evaluation and (re)habilitation.
- Special Educator - He/she is responsible for the academic part of children with special needs.
- Psychiatrist or psychologist - does psychological evaluation and expectations counselling.
- Social worker - provides funds and mental support.
- Teachers of the child candidate - assist in educational planning.
- Parents/Guardians of the hearing impaired child - provide mental and financial support to the child.
Different procedures are followed while performing cochlear implantation for children and for adults. Let’s have a glance at them -
For Children -
- Audiological Evaluation
- General case history
- Behavioural Observation Audiometry (BOA)
- Electrophysiological Assessment - ABR/BERA, ASSR, OAE
- Physiological Assessment - Impedance Audiometry
- If hearing loss is present, then the Hearing Aid trial is done
- Aided and Unaided Audiogram or
- Aided and Unaided Free Field Response
- The candidate is sent to ENT for Medical Candidacy Evaluation
- The candidate is sent for Psychological Evaluation for IQ Test
- The candidate is sent to Speech-Language Pathologists, who make the complete Speech and Language Evaluation Report.
For Adults -
- Audiological Evaluation
- Pure Tone Audiometry
- Speech Audiometry
- BERA (if required)
- Aided/Unaided Response
- The candidate is then sent for Medical Assessment for CI Candidacy
- Radiological Assessment (CT Scan, MRI)
As the above tests are done, a certified ENT Specialist or Surgeon does the surgery, which usually takes 1 to 3 hours. After a successful surgery, the Audiologist will proceed towards activating the device and fine-tune its settings based on your specific requirements, over a few follow-up sessions.
Cochlear Implants are different from hearing aids, as unlike the latter, they do more than just amplifying sounds - they make an exact replication of the sound, making the hearing experience much more natural. Cochlear Implant is a long-time solution for people with severe to profound hearing loss. If you are a good candidate for a Cochlear Implant, then get it done from a specialist Cochlear Implant centre without any delay. The sooner you get an implant, the sooner you can start enjoying life better.