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March 7, 2004

Cochlear implants new hope for deaf

From: Times of India - India - Mar 7, 2004



HYDERABAD : How do people born deaf or those who have completely lost hearing capacity due to certain infections communicate? For long they have had to resort to sign language, lip reading and to a small extent rely on hearing aids to cope with the external world.

But is there a way to restore the sensation of sound to those whose hearing apparatus is completely defunct?

There seems to be some hope for such people in the form of cochlear implants. But the forbidding cost — almost Rs 5-10 lakh — at which these surgical implants are being made available and lack of post-operative care is leaving many people disappointed.

Profound hearing loss is characterised by inability of the ear to receive sound and send signals to brain, which makes sense out of them.

This is caused by defect in the inner ear (cochlea) arising out of genetic disorders or infections such as meningitis or typhoid. Hearing aids are of no help here as they merely amplify the sound and cannot transform it into signals that can be comprehended by the brain.

In such conditions cochlear implants have been found to be effective in restoring the sensation of sound.

These implants do the work of the inner ear. The implants convert the sound from the environment into electric signals and send them to the brain.

"It is a complex mechanism which is accomplished by a set of electronic devices. The devices have to implanted through surgery. The sound created is quite different from the normal one. It requires training under an audiologist to get adjusted to such sound. Best results have been found among children operated below the age of two," said Dr E C Vinayakumar, an ENT specialist at a city corporate hospital where these surgeries are performed.

The implant system consists of a microphone, a sound processor and a set of electrodes. The microphone placed behind the ear taps sound from the environment. This sound is sent to sound processor, which is placed on the back of the person.

The sound processor selects and codes the elements of sound that are most useful for understanding speech. The codes are then transformed into electronic signals by a stimulator and sent to a set of electrodes — ranging from 6 to 22 — implanted in the inner ear through surgery.

Each electrode in this set has been specifically programmed to deliver sounds that vary in loudness and pitch. These electrodes then stimulate the appropriate hearing nerve fibres, which send the messages to the brain.

"The system works only if the nerve fibres are in place and are functioning," said audiologist G Srinivas.

"A complex set of tests need to be performed for determining patients eligible for this transplants. The implant can be effective only if there is proper training to the patient," he added.

Lack of proper training for people implanted with cochlear device is a major problem cited by patients.

"There are very few trainers and the cost of the implant is quite high as it has to be imported," said Rangamamba, whose son Krishna Teja has undergone the surgery. While this might be true there is also a lack of awareness about the role and ability of such implants, said V U Nandur, speech pathologist at Government ENT Hospital .

"Cochlear implants are not quick-fix solutions. These are meant only for those who lose hearing ability midway in life and cannot cope themselves with speech therapies. For those born with hearing defects the traditional therapies of speech reading hold good results. One must understand that speech is a learnt behaviour through prac tice," he said

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