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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.
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
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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.
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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.
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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.
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