profound hearing loss can start hearing with Cochlear Implants and early
intervention can change the life of a child for the better, explains Dr.
Mohan Kameshwaran Managing Director and Senior Consultant of Madras ENT
Research Foundation (MERF), Chennai, India. Medindia reports on
Ear is divided into three parts i) External Ear - the outer
portion and the pit (ear hole) ii) Middle Ear - deep to the eardrum which forms
the boundary between the external ear and the middle ear and iii) Inner Ear,
the sense organ. The inner ear in turn is divided into two sections where the
'cochlea' is concerned with hearing and the 'bone labyrinth' maintains balance.
So any hearing loss may be due to problems in the external or middle ear,
which is called Conductive Hearing Loss
. It could also arise from
problems in the inner ear or the nerve, which connects to the brain (auditory
nerve). Such hearing loss is called Sensorineural Hearing Loss. 'Sensory'
refers to the inner ear and 'Neural' refers to the 'nerve'. Conductive Hearing
Loss is easy to correct depending on the cause of the problem with standard
medical or surgical procedure. For example in case of an ear infection
leading to perforation of the eardrum, a procedure called Tympanoplasty is done
to close the hole.
However the real challenge lies in enabling hearing
in people with Sensory Hearing Loss.
Sensory Hearing Loss could either be congenital (by birth) or
acquired (later in life) due to various causes. Congenital Hearing Loss is the
commonest abnormality in infants. 2 or 3 out of 1000 infants are born with
profound hearing loss. In 99% of these children the cochlea is damaged. The
very fine cells in the cochlea called the 'hair cells' are concerned with
hearing. These cells may be damaged for various reasons or may not have developed
at all leading to profound hearing loss. However, the nerve connection beyond
the cochlea remains intact. If the cochlea can be bypassed then hearing can be
enabled. Sensory Hearing Loss of later life could be because of viral
fevers such as chicken pox, mums, meningitis, brain fever, toxic infections
like typhoid and even excessive noise, loud blasting crackers, and excessive
mobile phone usage. Acquired diseases such as otitis media, ear infections,
hereditary diseases, which may manifest later like otitis sclerosis, may also
lead to deafness.
versus Cochlear Implant:
People, with partial damage of the inner ear but
with some residual hearing can benefit from hearing aids, which merely amplify
sounds. However concerning people with profound hearing loss, even if sound
were amplified it would still remain ineffective because of lack of residual
hearing. So candidates with profound hearing loss who cannot get adequate
help from hearing aids can benefit from a Cochlear Implant because sound gets
picked up and broken into its component parts and converted into electrical
This electrical energy is transmitted across the skin by radio
frequency and stimulates a set of electrodes, which are implanted surgically
into the cochlea (inner ear). The implant bypasses the cochlea (damaged organ)
and stimulates the nerve beyond the cochlea and provides hearing. So unlike the
hearing aid, a Cochlear Implant does not rely on residual hearing. Cochlear
A Cochlear Implant has two components. One component is surgically
implanted inside the cochlea, which comprises of a set of electrodes. And a
receiver stimulator is placed on the side of the head on the skull under the
skin. Second component is an external unit consisting of a microphone, which
collects the sound and a speech processor (minicomputer) breaks it into
component frequencies. Appropriate electrical signals are generated in the
speech processor. These signals are then fed into an antenna, which couples
with the implanted portion under the skin (receiver stimulator) and across the
skin by means of a magnet. So the external portion is the antenna, the
internal portion serves as the receiver stimulator with the skin in between
them and a magnet couples the two components. So the external portion goes to
the electrodes and stimulates the cochlea, which enables transmission of sound.
Prior to an implant a child goes through investigations
called 'audiological test battery' done to ascertain the level and type of hearing
loss. Depending on the results a hearing aid or a Cochlear Implant is provided.
The sophisticated investigations can be done on the day of an infant's birth.
In many countries Universal Newborn Screening is mandatory where infants are
screened before they go home. Failure of early intervention could lead to loss
of language acquisition, which is based on hearing. So if a child is born deaf
then dumbness (lack of speech) sets in. The best age to correct deafness
is below the age of 3. After the age of 5 results diminish and beyond the age
of 10 it becomes almost impossible to develop language even with interventions
because brain has a critical period to learn language beyond which child will
not develop language.
"Early intervention has helped children develop
normal language, join regular school. Some have even made it to Ivy League
schools and reputed institutions in India" says Dr. Kameshwaran. Microsurgical
Post investigations, Cochlear Implant is a microsurgery
procedure lasting for one and half hours done under full anesthesia. The
candidate is then discharged after 48 hours. On the tenth day sutures are
removed and the device is activated on the 20th
day i.e. three weeks
after the surgery. The day of activation in a child is called the day of
the auditory age or the day the ear is born.
Language development takes
10 to 18 months. During this period a child is put through auditory
habilitation, which is different from speech therapy. Auditory
Habilitation focuses on teaching a child to listen with the intent to develop
language skills. Hearing does not mean listening. Listening has to be taught in
whom hearing is enabled.
The mandatory auditory rehabilitation is for a
period of 1 year with specialist called 'Auditory Habilitationist'. When Cochlear
Implant is Unneeded:
Post lingual people are those whose language has
developed but have lost hearing whereas Pre-lingual people are those born deaf.
Post lingual people can benefit from an implant at any age provided the
period of auditory deafness is not more than 20 years because they have already
The youngest candidate treated in this clinic was as
young as 6 months old and the oldest candidate, 80 years old. Cochlear Implant
cannot be done or is not needed when:
person and past 10 years in which case language cannot be developed
person with either the cochlea or the cochlea nerve not developed. But such
occurrences are only 1 % in which case, instead of a Cochlear Implant, Auditory
Brain Stem Implant is done where chips are implanted in the brain
Cochlear implants are cost effective in the long term
considering the sound future of the child. The cost of an implant is
anywhere between Rupees 5 lakhs and 11 lakhs depending on the model of the
According to Dr. Kameshwaran, "Real problem is coming up front
with the cost. In many countries Cochlear Implant is compulsory and is funded
by the government or insurance companies. So it can be done in India also. NGOs
for their part can actively involve in screening and detecting deafness and in
correcting with Cochlear Implant by arranging for funds for kids. Because
deafness is the truly correctible handicap which transforms a person from being
a burden to the society to a productive citizen. A country is truly developed
and ethical only if every child born deaf can avail health care services such
as Cochlear Implant and must not be ignored just because the child is born into
a poor family".