What Is a Cochlear Implant?
Cochlear implants, or electronic implants, are electronic devices used to help compensate for damage in your inner ear due to a variety of causes, such as age deterioration, a birth defect, or another cause. They are made up of an external processor and an internal electrode designed to work together to deliver processed sound signals directly to the auditory nerve.
The internal electrode is threaded into the cochlea using a simple surgical procedure. This component receives digitally processed sound signals produced and transmitted by the external processor and then transmits them to the auditory nerve, bypassing the auditory system. Hearing aids, by contrast, send processed sounds through the ear canal and the auditory system.
Since the FDA granted approval for the use of cochlear implants in the 1970s, technology has continued to improve the performance capabilities of the device. Today’s electronic implants are far more efficient than they were a few decades back, thanks to advancements in digital technology, which has had a significant impact on the processing and performance capabilities of hearing implants, just like they have with cell phones and other electronic devices.
Cochlear implants do not cure hearing loss, but as a replacement for hearing aids or used along with them, they often provide the much needed alternative solution to overcome individual hearing loss challenges, especially in individuals who have experienced limited success from the use of hearing aids.
Hearing Aid vs. Cochlear Implant
Hearing aids amplify sound and rely on the integrity of the hair cells of the inner ear. Patients with severe to profound hearing loss may, therefore, obtain limited or no benefit for speech perception. A cochlear implant on the other hand bypasses/replaces damaged hair cells and directly stimulates the auditory nerve. The electrodes in the internal component of the implant provide the "electrical spark" that is picked up by the nerve and taken to the brain for interpretation. Because these electrodes lie along the length of the cochlea, it is possible to have access to the full range of sounds even where there were no hair cells present.
t is important to note that the insertion of the electrode array results in total hair cells loss; consequently, a hearing aid cannot be used in the implanted ear.
How the Implant Works
Each implant system consists of two parts: an internal component and an external component.
Internal Component
The internal component consists of a decoder and magnet housed in protective casing. The electrode array extends from this casing. The surgeon will drill into the skull to make a "bed" for the decoder. The remainder of the internal component sits on the skull but under the skin. The magnet picks up the information provided from the external components. The internal component then determines which electrodes will fire with what power/current.
External Component
The external components consist of a microphone, a series of cords, a transmitting coil and a speech processor. Each part must be worn in order for the device to work. The microphone picks up sounds preferentially from the front of the listener and transmits the sound along the long cord to the speech processor. The speech processor contains a program individual to each listener indicating the minimum amount of current needed for a sensation of first hearing and the maximum amount of current tolerable. This program extracts the most important aspects of the incoming speech signal and transmits this information back up the long cord across to the transmitting coil. The signal travels across the skin via radio frequencies to the internal component. As mentioned earlier, the decoder of the internal component takes this information and determines which electrodes will fire and with what power. This processing of sound takes place in real time, not like a foreign film where the voices and lip movements are not in synchrony.
Cochlear Implant Process
Assessment and Surgery
All candidates undergoing assessment will first go through detailed audiological assessment and counselling. The initial appointment usually takes 1.5 to 2 hours.
If the results of the initial assessment suggest that an individual is a potential candidate, then further testing is scheduled. This includes a high-resolution CT scan, balance test (VNG) and a follow-up appointment with one of the program’s surgeons. Once all appointments are completed then an individual’s candidacy for cochlear implant surgery can usually be confirmed during a Cochlear Implant Team meeting.
If the initial testing does not suggest candidacy at that time, patients are asked to resume follow up care with their local hearing professional(s).Confirmed candidates for cochlear implant surgery are placed on a waiting list.
Post Surgery
- After surgical placement of the implant, a four week period is required to allow adequate healing of the incision site. Initial activation of the cochlear implant (hook-up) is typically a 2 hour procedure. During the activation, the device is adjusted and tuned using a computer.
- Reprogramming, for which the patient must return to the centre, is done approximately one week following activation, and then periodically over the next few months until stimulation levels stabilize. After the first year, patients will be asked to return to the centre at least annually for reprogramming, an equipment check and a formal evaluation.
Selection Criteria/Candidacy for Cochlear Implant
Adults
Adults must also meet a minimum set of criteria to be considered for cochlear implantation:
- 18 years of age or older
- moderate to severe/profound hearing loss with limited benefit from optimally fit amplification
- obtain limited or no benefit from traditional amplification
- spoken language as a primary mode of communication
- no medical contraindications
- strong motivation and commitment
- realistic expectations
The benefit provided by a cochlear implant CANNOT be predicted with certainty. All users, however, obtain environmental awareness and may experience improved lipreading ability, as well as gains in speech understanding through audition alone.
Children
The evaluation process of the cochlear implant is uniquely suited to the child's needs and abilities. Children and their families who decide to pursue the cochlear implant as an option must, however, meet a minimum set of criteria:
- 12 months to 17 years of age
- bilateral severe to profound SNHL (degree of hearing loss necessary is dependent upon age)
- obtain limited or no benefit from traditional amplification
- no medical contraindications
- spoken language as a primary mode of communication
- speech perception abilities that correspond to predicted aided potential
- educational placement with strong auditory component
- strong motivation and family support
- realistic expectations
Early Intervention
The ability to detect sound is critical to a child's ability to learn speech and language. The absence of such sound can have profound effects on speech and language development as well as the educational achievements of children.
Given the potential impact on a child's life, it is critical that hearing impairment in children be detected early. Similarly, early referrals to the Cochlear Implant Team are crucial to ensure that maximum benefit is obtained from the cochlear implant.
An Auditory Verbal Therapist works closely with children and their families to assess and foster children's listening and language skills. Community therapists generally provide this service.
Please note: Criteria changes regularly, so candidacy is considered on an individual basis.
At Vedanta Speech and Hearing, we understand how crucial hearing is for overall well-being and communication. Our team of highly skilled and experienced professionals is dedicated to providing comprehensive hearing assessment and personalized solutions.
If you have any queries related to cochlear implant rehabilitation, you can visit Vedanta Speech and Hearing. They specialize in providing rehabilitation services for individuals with cochlear implants. Their team of experts can help answer your questions and provide guidance on the rehabilitation process.