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Cochlear Implant (CI)

What is a Cochlear Implant (CI)?

A CI is an electronic device designed to restore a level of auditory function to people with severe to profound hearing loss and who do not benefit from conventional amplification (hearing aids). It is an alternative solution when traditional attempts to improve hearing ability, with powerful hearing aids, no longer provide assistance. One part of the implant is surgically placed inside the inner ear while the other external part is worn behind the ear. Unlike a hearing aid that amplifies sound to make it loud enough for an impaired ear, a (CI) delivers electrical stimulation to the inner ear or cochlea and bypasses the damaged hair cells, directly stimulating the hearing nerve.

How Does a Cochlear Implant Work?

In normal hearing, complicated parts of the inner ear convert sound waves in the air into electrical impulses. These impulses are then sent to the brain, where a hearing person recognizes them as sound. A cochlear implant works in a similar way. It electronically finds useful sounds and then sends them to the brain. Hearing through an implant may sound different from normal hearing, but it allows many people to communicate fully with oral communication in person and over the phone.

Who is a Cochlear Implant Candidate and what is the benefit?

Children and adults who have severe or profound sensorineural hearing loss and derive minimal benefit from hearing aids may be candidates for a cochlear implant.

The benefit that an adult receives from an implant depends on several factors: their degree of hearing loss, their ability to understand speech before receiving the implant, experience using a hearing aid, and the length of time they have been severely or profoundly deaf. Generally, the more experience a person has had with hearing and the shorter the duration of their deafness, the more benefit they can expect to receive. Benefits vary from excellent, the ability to understand speech without visual cues (as on the telephone), to minimal, the improved ability to lip-read.

Young children are excellent candidates for cochlear implantation because they have robust central nervous system plasticity, which allows them to make use of the sound the implant provides. Children implanted early, who do not have other significant developmental disabilities, and when coupled with intensive post-implantation speech and language therapy, may acquire age appropriate speech, language, developmental, and social skills. They are usually schooled in mainstream educational settings.

The best age for implantation is still being debated; however, research indicated that children who receive hearing early have the best results.

Making the Decision

When a child is diagnosed with profound hearing loss, the family must decide how to address the child’s fundamental communication needs. Options might include Total Communication which is a combination of sign and spoken/auditory communication, or strictly oral/aural communication which is speaking and listening. For many children with severe-to-profound hearing loss, hearing aids may not provide adequate benefit even after extensive experience and auditory training. Families arrive at the point of considering a cochlear implant at various stages in a child’s development. Each child presents with a unique background and circumstances that can impact the child’s potential to benefit from the device. Additionally, families often have varied degrees of information regarding cochlear implantation and the expected outcomes. Families are encouraged to speak with audiologists, speech language pathologists, educators, physicians, and/or counselors who are familiar with the cochlear implant process. Families also are encouraged to talk with parents of children who have received cochlear implants. Active participation in this process is critical to making an informed decision for your child in regard to a cochlear implant.

Evaluation and Preparation for Cochlear Implants

Patients undergo several tests and preparation to determine if they are good candidates for cochlear implantation. The evaluation process is a team approach. Obtaining accurate audiological information is at the core of making appropriate recommendations related to cochlear implant candidacy. It is important that the testing be done by a specially trained pediatric audiologist who is experienced in fitting and facilitating pre-implant hearing aid use. The team also includes aural re/habilitation specialist, speech and language specialists, an educational consultant and, of course, the operating surgeon. The criteria for implantation becomes:

The criteria for implantation:

  • Audiologic information: is the hearing loss severe enough (Severe-to-profound sensorineural hearing loss in both ears)
  • The hearing aid is not sufficient (limited benefit from hearing aid as determined by specialized audiological testing)
  • Speech and language: what is the level of the child's present speech and language and what postoperative interventions are necessary?
  • Otological, medical and radiological tests: no contraindications
  • High motivation to participate in re/habilitation sessions
  • Appropriate expectations

Cochlear Implant Procedure

Surgery

Surgery is performed while the patient is under general anesthesia and lasts between two to three hours. The procedure requires an overnight stay at the hospital. Prior to the surgery, a small portion of hair is shaved where the internal device (receiver stimulator and electrode array) will be placed. The surgeon makes an incision behind the ear and forms a slight depression in the mastoid bone, where the internal device rests. The surgeon then creates a small hole in the cochlea and threads the electrode array of the internal device through this hole. The incision is closed so that the internal device is beneath the skin. Finally, the incision is closed and a pressure bandage is applied for one to two days. Generally the swelling will subside within 2-4 weeks after the implantation. Discomfort after surgery is minimal.

Activation of the Cochlear Implant

Four to six weeks after surgery, after the incision has healed, the external components of the device can be programmed and activated. There is no hearing ability from the implant until this is done.

Attaching the headset and fitting the headset

After the incision has healed and the swelling has subsided, an audiologist attaches a headset. The headset contains an external magnet that is aligned with a magnet implanted inside the head during surgery. Adequate magnetic attraction is necessary to hold the headset over the internal receiver/stimulator so that information can be transmitted across the skin via radio frequency.

Cochlear implant check

The device is checked through a computer system, by communicating information between the cochlear implant and the external speech processor. Every component, including each electrode, is checked to make sure it is working properly.

Programming the speech processor (Hearing Sound for the First Time)

The audiologist will create the initial program or “MAP”, the map is a set of instructions that tells each electrode how to stimulate the nerve endings in the cochlea which will allow the patient to hear sound for the first time with the implant. Each electrode is activated by the audiologist who will be looking for the softest levels of stimulation required to generate a response (threshold or “T” levels) and for comfortable listening levels (comfortable loudness levels “T”). As each electrode is turned on, very small increases of electrical current are delivered to the hearing nerve until the patient hears a soft beep or tone. Once the softest hearing level is set, the patient listens for an increase in loudness until these beeps or tones become comfortable to hear. These steps are repeated until all electrodes are set for soft and comfortable levels.

Once a map is created and downloaded into the speech processor, the speech processor is turned on, and the patient hears through the cochlear implant for the first time. On this first day, speech usually sounds garbled or high-pitched and environmental sounds may be difficult to identify. Over time, speech and environmental sounds become clearer and more natural. The child’s reaction to the initial activation of the device can range from happiness and excitement to fear or alarm to little or no reaction at all. It is important to realize that each child will react differently to the new sound through the implant.

Learning how to use the external equipment

After the final program adjustments have been made the recipient and or the child’s family is instructed on the operation, care and maintenance of the device and accessories. Information about precautions, warranties, repair and insurance is also shared with the patient and or the family.

Programming Sessions

Multiple visits are necessary as part of the cochlear implant process, in order to obtain and maintain optimal performance from the device. Patients return the day after activation for a re-check — and again after two weeks, one month, three months, six months, nine months and one year. After the first year, patients usually schedule every 3-6 months.

Rehabilitation after Cochlear Implant Surgery

Rehabilitation involves training the brain to understand sounds heard through the cochlear implant. Since the cochlear implant restores awareness for all sounds, patients sometimes are overwhelmed initially. Speech and every day environmental noises sound different from what they remember or what they are hearing for the first time; as for children, it takes time for the brain to recognize what these sounds mean. This process is ongoing and is best achieved by wearing the speech processor continuously during waking hours.

Aural re/habilitation and speech therapy is a must to help retrain the brain to hear.

© 2011 JISH Jeddah Institute for Speech and Hearing, all rights reserved.