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Cochlear
Implant
Loss of
hearing is the least recognized, physical ailment. More people
suffer from it than from heart disease, cancer, blindness,
tuberculosis, multiple sclerosis, venereal disease and kidney
disease combined. Yet we pay less attention to hearing loss
than to any other major affliction.
Perhaps
this is because hearing loss is invisible and usually painless.
It is a hurt that does not show; therefore, it seems less
important than other disabilities. But for those who are profoundly
hard of hearing or deaf, and who live in a world of silence,
the emotional pain is often devastating.
A Cochlear
implant provides useful hearing and improved communication
ability for people who have profound to total hearing loss.
What
is a cochlear implant?
A cochlear implant is a medical option for individuals with
severe to profound hearing loss. It can be used by deaf born
children and adults with acquired profound hearing loss. By
stimulating the sensory cells in the cochlea, cochlear implants
allow recipients to perceive environmental sounds and speech.
Many profoundly hearing impaired individuals view the Cochlear
Implant as a tool to interact with the hearing world and broaden
their educational, occupational and social opportunities.
A cochlear implant consists of two components: an implantable
and an external device.
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The
external components consist of the microphone,
the speech processor, and the link that allows communication
with the implanted parts. Also, the power supply for both,
the external and the internal components, is provided
by the external part. |
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The
internal parts consist of the receiver, the stimulation
electrode, and the reference electrode. The signal is
received via a radiofrequency link through the intact
skin. The signal is then processed and used to stimulate
the main electrodes inside the cochlea in a designated
pattern. |
How
does a Cochlear Implant work?
Contrastingly however, a cochlear implant is an excellent
method of treatment and intervention for patients who have
levels of hearing loss in the severe to profound range or
those who can no longer benefit from traditional amplification/hearing
aids. The cochlear implant is similar to a pacemaker.
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First
(1), the microphone gathers sound from the environment
and sends it to the speech processor. The speech processor
changes sound to a specially coded electrical signal.
Then (2), the message is sent along the cable and up
to the headpiece (coil).
The signal travels from the transmitter of the headset
across the skin to the internal receiver. From the receiver,
the sound moves down the electrode array to each individual
electrode contact.
Electrical
stimulation (“firing”), generated by the array (3),
is distributed to different areas of the cochlea. Auditory
nerve captures the electrical signal and sends it to
the brain to be interpreted as sound & speech. In
the absence of the external speech processor (i.e. removing
it at night to sleep or when bathing, showering, or
swimming), the patient will be unable to hear sounds
or speech from the environment. The two pieces work
together to provide the patient with quality hearing
and speech comprehension.
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The
cochlear implant consists of two distinct pieces; one is an
internal receiver/stimulator (surgically implanted) and the
second is the external speech processor, which is worn on
the outer ear (pinna) and looks similar in appearance to a
behind-the-ear hearing aid. Both of these pieces must be present
for the system to work for the patient as they are coupled
across the skin and through the hair by magnetism. The internal
receiver houses a magnet and the external portion magnetizes
to the internal connection..
Hearing aid vs. Cochlear implant
A cochlear implant is uniquely different from a hearing aid.
A hearing aid works by amplifying and making the everyday
sounds in the environment louder. By increasing the level
of the sound, this can often surpass the patient's threshold
for hearing as determined by his/her level of “active” hearing
loss and simultaneously improving the patient's ability to
hear and communicate. Traditionally, hearing aids are adequate
for patients with mild to moderately-severe sensorineural
hearing losses as well as patients with inoperable forms of
conductive hearing loss. Unfortunately, people with severe
to profound hearing loss suffer from extensive hair cell damage
and they cannot make use of the sound amplified by the hearing
aid. For these patients, sound is imperceptible.
In contradistinction a cochlear implant is not a hearing
aid. Rather, it is a neural prosthesis that helps to restore
hearing in people with severe to profound hearing loss. The
patient's traditional means of hearing is then replaced with
electric hearing through the cochlear implant.
What
can be expected from using the Cochlear Implant?
The implant
does not restore normal hearing but does improve the person's
ability to hear environmental sounds, to hear rhythms and
patterns of speech, and to use speech reading (lip reading)
better. Hearing sounds with a Cochlear Implant is different
from normal hearing. Recipients have to learn to interpret
sounds that they may hear. It may take some time and experience
with the Cochlear Implant before recognition improves.
Rehabilitation
and training with the cochlear implant
The first
few sessions of rehabilitation involves using a computer to
program the speech processor to the patient’s own responses.
It often takes several sessions to fine tune the device, making
it suitable for the patient. Six months and one year after
beginning use of the implant, the patient returns for further
testing and training. These follow up visits continue annually
(every 6 months for young children).
After
fitting to the external device, one month is devoted to weekly
rehabilitation sessions. This is to acquaint the patient fully
with the implant equipment and it’s most efficient and effective
use. This program involves both the patient and the family;
it is directed toward utilization of the new auditory clues
available, as well as improvement in communication ability.
Each patient is given instruction in a home practice program
designed to continue the graining progress with the implant.
It must be kept in mind that learning to effectively and comfortably
use the signals provided by the implant takes considerable
time and effort, perhaps up to a year. Patience is required
by the implant user, the family, and acquaintances. Six months
and one year after beginning use of the implant, the patient
returns for further testing and training. These follow up
visits continue annually (every 6 months for young children).
The devices
available now use a pattern of stimulation that is much more
natural than what was used earlier; it is like playing a chord
of three notes together on a piano. “In the old days, the
notes were played separately on the implant. Now the circuits
in the implant allow for a faster transfer of information
so that the chord can be played all together in your ear.”
Speech
sounds are much like a chord on the piano. They contain different
pitches at the same time. The new, faster transmission thus
makes for more natural speech sounds. Your brain takes this
information to put together to tell you exactly what information
is coming to you from the outside world.
If you
have recently lost your hearing, the chance that you can understand
what you are hearing with an implant is much better because
you are more familiar with the information you receive. That
is why the amount of time since you lost your hearing is one
of the most important ways to predict how well you will do
with an implant.
Dr.Kumaresh
Krishnamoorthy, M.S(ENT)
Head and Neck Surgery Fellowship (Buffalo, USA)
Neurotology & Skull Base Surgery Fellowship (Cincinnati,
USA)
Senior Consultant in ENT - Head and Neck Surgeon and Skull Base
Surgeon
Apollo Hospitals, 154/11, Bannerghatta Raod, BANGALORE 560 076,
INDIA
Phone: 91-(0) - 99002 36819
Email: drkumaresh@drkumaresh.com
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