A sound remedy

Print edition : September 26, 1998

Cochlear implant technology, which holds out hope for even those with severe hearing impairments, receives wider attention in India.

Unlike visually impaired persons, who now have a radical remedy in transplants, the hearing impaired have had to be content with incremental improvements in conventional hearing aids. However, the cochlear implant represents a major medical technological advance and provides access to sounds even for persons with congenital hearing defects. After pioneering research on cochlear implants by Professor Graham Clark of the University of Melbourne, Professor W.P.R. Gibson and his team in Sydney set up the first cochlear implant centre for children in 1986. Six years later, encouraged by the Australian Govern-ment, International Coch-lear Implants (ICI) was set up.

ICI made major strides in the manufacturing, surgical and post-surgery aspects of cochlear implants. It established a presence in South-East Asia as well. The cochlear device can be implanted in adults as well as children, who are then helped through intensive post-surgical therapy to process and comprehend the sound signals they receive. More than 17,000 adults and children across the world today use cochlear implants.

In India, in the last couple of years, surgeons and audiologists at leading institutions, including the Kasturba Medical College (Deemed University), Manipal, the All India Institute of Medical Sciences, New Delhi, the Madras ENT Research Foundation (MERF), Chennai, and the Apollo Hospitals, Hyderabad, have carried out successfully more than 10 cochlear implants, using devices imported from ICI. The introduction of the specialised technique in India - attempted in only a few hospitals around the world - has brought down costs substantially.

ICI clinical adviser William Waytowych and (left) managing director Judy Wimble in New Delhi.-M. LAKSHMANAN

MERF, for instance, carried out its first two implants in March 1997 on two high-school boys who lost their hearing suddenly owing to viral infections. Although these cases were treated on a charitable basis and to demonstrate technology availability, MERF estimated each surgery to cost Rs.6 lakhs then. Today, some of the Indian hospitals offer the entire package, including post-surgical therapy, for Rs.4 lakhs. The imported cochlear implant device itself costs about Rs.3.7 lakhs. MERF recently had its first patient from abroad - a Sri Lankan whose case was sponsored by President Chandrika Kumaratunga. MERF has also started a paediatric implant programme for the treatment of congenital hearing defects.

The full potential of the implant device can be achieved only through intensive post-surgical therapy, involving rehabilitation, audio therapy and speech-language recognition, and a training programme. In this area, ICI has had a headstart over its counterparts elsewhere. The audio therapy extends over a year and requires the assistance and coordination of an audiologist, a habilitationist, a speech-language pathologist and the family members of the patient.

William Waytowych, clinical adviser at ICI, and Judy Wimble, managing director of the company, who were in New Delhi recently, spoke to Sudha Mahalingam. Excerpts:

What is the latest device that provides relief to the hearing impaired?

Waytowych: There are many devices that help improve hearing. Hearing aids have gone through many stages of development over the years and now there are even digital hearing aids. But the device that we, at International Cochlear Implants, have developed is the cochlear implant, which represents a higher level of sophistication. It was introduced 10 years ago, after years of research. It has been accepted by the Food and Drug Administration in the United States as a safe and effective device to improve hearing.

How is the cochlear implant different from conventional hearing aids?

Waytowych: The cochlear implant has evolved from conventional hearing aids, but it represents a quantum jump in technology over the latter. The cochlear implant can be used on a person with a severe hearing impairment; it can even be used on a profoundly deaf adult suffering from congenital deafness. While conventional hearing aids stimulate hair cells in the inner ear, a cochlear implant directly stimulates the nerve cells, bypassing the hair cells. This accounts for the great difference in the results produced by the two devices. In hearing impaired persons, sometimes the tiny hair cells, which transmit sound, are either entirely missing or are very sparse, so much so that the degree of effectiveness of any device designed to stimulate hair cells can only be as much as the capacity of the hair cells to transmit sound. Since a cochlear implant is connected to the nerves and not to the hair cells, it can be used even by those who do not have any hair cells at all.

What causes impaired hearing? Are there any types of deafness that cochlear implants cannot address?

Waytowych: In about 60 per cent of the cases, the cause of deafness is unknown. In most cases, it is genetic. Where it is acquired, it can be owing to many factors, including the infusion of toxic drugs normally administered for high fevers and so on. As we said before, even those without hair cells can use this device. Normally, in adults, with advancing age, owing to various factors, including diet and pollution, hair cells get sparser, resulting in partial loss of hearing. Roughly about one in a thousand will have the kind of hearing problem that cannot be addressed by the cochlear implant.

How does the cochlear implant work?

Waytowych: There are two or three types of implants. The cochlear implant, a thin and tiny device, is about two inches in length. It is surgically implanted behind the earlobe, just beneath the skin. The surgery itself requires just an overnight stay in hospital. The implant has 24 electrodes at the tip, each for picking up a different frequency of sound. The electrode ray is made of bio-compatible material. The middle ear is drilled and the electrode ray is anchored to it. There is an antenna and a magnet in the implant. Mapping of the device is done a week after the surgery. This will enable the antenna to pick up the sound, which is then transmitted to a processor (the size of a small calculator). This is kept separately on the person, say in the pocket. The processor then selects and codes useful sounds and sends them back to the transmitter, which sends the codes across the skin to the receiver. The receiver/stimulator then converts the codes into electrical signals. The electrical signals are then sent to the electrodes to stimulate the hearing nerve fibres. These signals are then recognised by the brain as sounds, thus producing a hearing sensation.

Has there been any research to eliminate the need for a processor to be carried separately?

Waytowych: Both the processor and the implant have been getting smaller and smaller in size. There have been two updates in the last 10 years since we started this process. It is conceivable that the processor will become even smaller in the future.

How many cochlear implants have been done since the device was first developed?

Waytowych: About 17,000 people the world over use cochlear implants. Of them 7,000-8,000 are children. In fact, the youngest child to have an implant was eight months old. It must be emphasised that the younger the implantee, the greater the benefit from the device, since young children have less difficulty in picking up speech and language skills than adults.

How many companies manufacture the device? Is yours the only one that conducts implant surgery as well?

Judy Wimble: There are three companies engaged in the manufacture of the device; ours is the oldest. Our device comes with a 10-year warranty and the processor has a three-year warranty. The implant is almost permanent although we say it is good for 10 to 15 years. The implantation surgery is done by Professor W.P.R. Gibson and his team in Sydney. While there are other places where the device is surgically implanted, we provide a back-up service in the form of follow-up by the habilitationist, the audiologist and the speech-language pathologist. Such follow-up is crucial to derive maximum advantage from the device. The surgical implantation itself can perhaps be done anywhere. Especially for a person who needs to recognise and make sense of sounds, not just be able to hear them, follow-up therapy and fine-tuning are essential.

How much does it cost?

Judy Wimble: The cochlear implant costs 25,000 Australian dollars, and the processor costs A$10,000 to 11,000, depending on the model. Another A$50,000 to 60,000 will be required for the surgery and the 12-month post-operative care by audiologists and others. In addition, the patient will have to bear the cost of travel to Sydney and a three-month stay there. Child patients require three months' stay before they can be discharged.

The surgery has to be done in Sydney. As such, the cost of the device and the cost of the surgery cannot be lower. However, we are planning to find some hospitals in India where we can train audiologists and speech-language therapists who can provide the follow-up services locally. Research is going on to fine-tune the device further and costs could come down over a period of time.

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