Australia is in the forefront in this field of surgery, with
America being one of the main pioneers, too. What is a
cochlear implant? Who will benefit from it, and does it
restore lost hearing?
The implant is an electronic device which is surgically
implanted in the skull behind the ear, and is activated by a
microphone worn outside the ear, and a speech processor which
is usually worn on a belt or in a pocket. Tiny wires are
inserted from the cochlea into the inner ear. The implant
does not amplify sound at all, but it bypasses damaged parts
of the auditory system and electronically stimulates the
hearing nerve, thus allowing people who are profoundly
hearing impaired to receive normal sound.
What is normal hearing? The ear consists of three parts which
play an indispensable role in hearing: the external ear, the
middle ear and the inner ear.
Sound travels along the ear canal of the outer ear, causing
the ear drum to vibrate. Three small bones in the middle ear
conduct this vibration from the ear drum to the cochlea, the
auditory, or hearing chamber of the inner ear. This is called
conductive hearing.
When the three small bones move, they start waves of fluid in
the cochlea, and these waves stimulate more than 16,000
delicate hearing cells, or rather, hair cells. As these hair
cells vibrate, they start an electric current in the auditory
nerve. This current travels to the brain, which recognizes it
as sound. This is called sensorineural hearing.
If there is some obstruction or disease in the external or
middle ear, the conductive hearing may be impaired.
Antibiotics or grommets (tubes in the ear) can usually
correct this. However, if the problem is in the inner ear, in
many cases the hair cells are damaged and do not function and
although the nerve fibers may still be intact and could
transmit electrical impulses to the brain, they do not `work'
because of the cell damage.
To date, over 80,000 adults and children world wide have
received cochlear implants. But how successful are they?
There are many factors that contribute to the degree of
benefit a user will receive from the implant. It also depends
on how long a person has been deaf, the number of nerve
fibers which are not damaged and perhaps, most important of
all, how motivated the person is to learn to hear. For
adults, previous good speech and communication skills with
only a short time since their loss are a great help towards
successful implants. However, cochlear implants are only
recommended for adults who get little or no benefit from a
conventional hearing aid.
In recent years, several hospitals have established a routine
hearing check on babies on the day they are born! In Israel
alone, there are four of these hospitals. There are about 1.5
per thousand babies born with a severe hearing impairment and
the earlier the intervention, the more likely the child will
be able to attend a normal school among children with normal
hearing. The implant is not usually carried out before the
age of 20 months or two years (unless the child has
meningitis). This is because the child is considered to be at
risk at this age, both from the general anesthetic and the
actual surgery, which takes about two hours.
Results have shown that implants done before the age of five
are very successful indeed. The child hears normal sounds but
does not connect them to anything. Till now, hand clapping
was a silent occupation. Traffic moved without sound, as did
Mommy's lips when she spoke to him. Some children show sheer
delight, others show surprise and even fear of their new
world of sound, and others seem to take no notice at all of
the change in their world.
In adults, the headset (microphone) and speech processor are
fitted about a month after surgery. The audiologist will
obtain comfortable listening levels for each of the tiny
electrodes in the ear, and uses this information to create an
individual program. In small children, the fitting is done
over a period of three months, with the audiologist seeing
the child two or three times a week for the first month, and
then once or twice each week for the next two months, to
obtain the correct individualized program, known as MAP among
professionals.
It takes about a year of regular monitoring for the family to
learn how to adjust and care for the equipment, for the
electrodes to be checked and adjusted, and for the child
himself to adjust. After that, it takes another year of
intensive speech and other therapy for the child to begin to
get the most out of his implant.
Doctors claim that even up to the age of ten, they get very
good results, although the brain is extremely flexible and
different nerve cells can more easily be taught to take the
place of damaged ones before the age of five. Thus, children
who were born with severely impaired hearing obtain correct
voice pitch and excellent communication abilities.
The sound input which a normally hearing child receives
straight after birth gradually translates itself into
meaning. The clink of a spoon, Mommy's footsteps, the
rustling of a candy wrapper, to mention but a few, are all
important sounds to the developing child. Not so the child
with a cochlear implant. He will have a normal input but will
have to be taught the meaning of the sounds. It is as
if we would be taken to China: we would hear the language,
but it would be Chinese to us and we would have to be taught
the meaning of each word.
If parents, teachers and speech therapists all work together,
this is of the greatest benefit to the child. Music therapy
is a very effective way of expanding auditory perception and
language skills. It seems to benefit the patients
emotionally, physically and socially. Apart from which it is
usually pure pleasure for the child.
I listened to a nine-year-old boy who had received a coclear
implant, pounding a drum recently. He spoke very
intelligibly, with fairly normal pitch, without the monotone
normally associated with hearing impaired people. His
teachers had worked very hard to integrate him into a regular
school, although he will still continue to receive years of
therapy. Finally, the external pieces which activate the
implant are designed to incorporate the rapid advances in
technology, which is an added glimmer of hope to worried
parents, who have to make the decision for their baby.
