Silence Gets Sound

From a single electrode to having 22 electrodes, cochlear implant devices have undergone rapid technological evolution, finds out Sonal Shukla

With one out of every 12 Indians suffering from some degree of impaired hearing, Cochlear Implants (CI) is a proven medical aid for individuals with severe to profound hearing loss. It gifts 'sound' to the ears of a person with profound deafness and gives him a chance to lead a 'near to normal' life once again. Since its discovery more than four decades ago, the rapid technological advancement of CI has proved to be a boon for one million deaf Indians. It is estimated that one out of 1,000 births require cochlear implant worldwide. According to experts, over 4,500 individuals in India have been benefited from this device so far, out of whom more than 80 pr cent are children.

According to Dr Sandra DeSa Souza, pioneer in CI surgery in 1987 and the first woman cochlear implant surgeon in the world, "There is a growing need for CI because of the increase in the number of infectious diseases, viruses and antibiotics which can damage the hearing nerve to an extent that the hearing aid won't work and CI will be needed. Moreover, increasing incidence of early detection of deafness in new-born babies and awareness have given an impetus to this need."

What is CI?

A CI is an electronic device that is surgically implanted into the inner ear (cochlea) of a patient with profound deafness (sensori neural hearing loss) to improve/ restore hearing. It differs from hearing aid as CI transmits electrical signals into the cochlea that excite the nerve endings inside the cochlea, thereby the signal passes to the brain. However, a hearing aid merely amplifies the sounds and the normal mechanism of hearing in the middle and inner ear is stimulated by the sound which is transmitted to the brain. Hence, the energy that is transmitted to the cochlea in a normal person or one who is wearing hearing aid is sound energy whereas in a CI it is electrical energy.

Says Dr Lt Col Ravi Kumar, Professor and Head, Department of ENT, Head and Neck Surgery, Sri Ramachandra Medical College & Research Institute, Chennai, "CI is probably one of the best inventions in the medical field. It is the first device that can restore one of the five senses i.e. hearing in a completely deaf patient."

Children with profound or severe to profound hearing loss, using hearing aids, cannot have access to sounds across the speech range. "A hearing aid is like a sophisticated amplifier that can only amplify the residual hearing in a person. This results in faulty speech production and limited language development," says Aziza Tyabji, Director, Aural Education for Children with Hearing Impairment (AURED), Mumbai. However, a CI directly stimulates the auditory nerve, making a wide range of frequencies available to the recipient.

Who Needs It?

"Research is being conducted to make CI as 'atraumatic' as possible so that it does not damage the residual function of cochlea" - Dr Milind Kirtane Consultant ENT surgeon Hinduja Hospital Mumbai

"There is a growing need for CI because of increase in infectious diseases, viruses and antibiotics" - Dr Sandra DeSa Souza ENT Specialists Jaslok Hospital & Research Centre Mumbai

"The problem is that the number of people coming up for the implant is certainly not that high" - Dr John Mathew Professor of ENT CMC, Vellore

Adults (post-lingual patients) who have lost all or most of their hearing later in life often can benefit from cochlear implants. They learn to associate the signal provided by an implant with sounds they remember. This often provides recipients with the ability to understand speech solely by listening through the implant, without requiring any visual cues such as those provided by lip reading or sign language.

CIs coupled with intensive post implantation therapy, can help young children (pre-lingual patients) to acquire speech, language, and social skills. Most children who receive implants are between two and six years old. Early implantation provides exposure to sounds that can be helpful during the critical period when children learn speech and language skills. "Almost 90 per cent of our patients fall in the category of pre-lingual," says Dr Milind Kirtane, Consultant ENT surgeon, Hinduja Hospital, Mumbai. According to experts, correct selection plays an important part to get a positive outcome from a CI surgery. "If you do not select your patient properly with pre operative measures and tests to evaluate the candidate first and just go and rush in and do an implant, then you might not get an ideal result," adds Dr Kirtane. For a post-lingual patient, it has been found that the age is not the limit and he/she still can be operated, however, the sooner the patient is operated after he/she becomes deaf, the better it is.

Teaming Up

Besides the advanced technology and the surgery, it is team approach that plays an important part not just in the selection of the patient but also in his rehabilitation after the CI surgery.

A CI centre typically consists of a team of professionals, i.e. ENT surgeon with special training in cochlear implantation, audiologist with special training in CI and an audio verbal therapist, who teaches the post-implanted patient to listen and then speak and lastly the parents, if it is a child. "These four components play a major role as we have to have an ideally suited patient. There should be a lot of stringent selection criteria for saying that it is a good patient for the cochlear implant by this team," shares Dr Kirtane. It is helpful if the department is equipped with tools for assessment of hearing loss in young children like otoacoustic emissions, BERA / ASSR, behavioural or VRA testing setup and tympanometry.

Rehab: Post-Implant

A CI enables the patient to hear and therapy enables the patient to understand what they hear. "Therapy required is known as the Auditory Verbal Approach, through which a child is taught to 'listen and speak. The younger the patient, the better the outcome," says Tyabji.

When CIs first came to India, the rehabilitation scene was abysmal. In the recent past, CI companies, have on a war-footing invited professionals from several countries to conduct workshops and training sessions, for those working with CI recipients in India. Cochlear Limited jointly with Ali Yavar Jung National Institute for the Hearing Handicapped, Mumbai has started a six-month training course in Auditory Verbal Therapy to increase the number of professionals equipped to manage pre and post operative management.

The therapy includes audiological management, which is the process through which each electrode is subjectively adjusted to maximise hearing thresholds. Each electrode represents a certain range of frequency, and with proper audiological management, the patient should be able to hear across the speech frequency range. Incorrect mapping results in compromised listening.

It also includes on-going assessment, informal as well as formal as it is most essential to evaluate the child's performance to set future goals.

Integration into regular schools: Children with CIs need good modeling and exposure to a lot of spoken language. If they are sent to special schools (as suggested by many school Principals), they will not get this exposure and in fact will pick up incorrect speech and language. “A combination of good surgery, correct audiological management and on-going therapy enables the child to communicate in spoken language and to become an integrated, contributing member of mainstream society," says Tyabji.

Body Worn Processor-PSP from Advanced Bionics	Body Worn Processor from Cochlear Company
Helix 90k HF 1J electrode implant from Advanced Bionics	Countour electrode implant from Cochlear Company

Why Less Interest

It is not profitable for any hospital to run a CI programme as there is a heavy initial investment in doing this surgery. "I am sure many hospital will come forward for doing CI surgery, but the problem is the number of people coming up for the implant is certainly not high. With the present set of hospitals I am sure that we can still manage the present demand," opines Dr John Mathew, Professor of ENT, CMC, Vellore.

From Better to Best

The first successful implantation was done in Australia by Prof Graham Clark in Melbourne in 1978. Since then, there have been many modifications and the device has become compact and more versatile. Improvement has been in design of implant / processor technology, miniaturisation and battery options of the device. CI technology has become more sophisticated over the years. With just a single electrode earlier, today, a modern CI has 22 electrodes.

"With improving electrode technology, we are able to try and preserve residual hearing. More reliable and sophisticated electronics mean better speech processing and longer lasting implants," shares Dr Pradip Uppal, Head- Dr Uppal E N T hospital, Thane. Today, the standard CI available in the worldwide market is multiple electrode implant. The technology has helped thousands of people listen, learn and talk since the first multi-channel cochlear implant surgery was performed in 1982.

Not Made in India

As of now, there are no indigenous CIs available in the market. A few years ago, under the aegis of Dr APJ Kalam, DRDO was tasked with the development of an Indian Cochlear Implant System, but there is no news about that. The Indian team from Armed Forces did visit Cochlear Limited, Australia for guidance in this matter. Dr Kalam's vision was to bring down the cost of the implant for the common man. However, experts still doubt the quality and acceptability of such an implant in the market. There are many advanced CI systems and all are available in India today. Mainly, there are four big companies manufacturing CIs, the largest of which is Cochlear Limited, Australia and followed by in no particular order, Advanced Bionics LLC, US; Medel, Austria and Neurelec, France.

Hybrids Hits the Market

The hybrid implant also known as 'Electro Acoustic Implant' is one innovation which is already in the market and is designed for patients with high frequency hearing loss who may have good low frequency hearing. It incorporates a specialised electrode designed to stimulate the high frequencies and complement their existing low frequency hearing. It is a combination of both hearing aid and a CI. Hybrid implant is already in use in Australia, but in India we have not done any hybrid implant yet.

Sounds of the Future

Worldwide, efforts are on to make CI more compact, in which the next level would be Totally Implantable Cochlear Implant (TICI). This implant is still in its research phase. According to Dr Kirtane, the biggest problem with TICI is that since even the microscope will be inside the body, all the body noises can be heard. "It might not be suitable for the children at the moment because it is much more bulky. Battery does not last for ever. So, after the battery life goes then it will become like any other implant," says Dr Mathew.

R&D

Research is on towards refining speech processing. Hence, the external processor in the CI is being refined to give the patient, better speech processing, especially in noisy surroundings. "Research is being conducted to make CI as 'atraumatic' as possible so that it does not damage the residual function of cochlea. On the surgical side, the surgery techniques are being improved to do minimal damage or to reduce the amount of damage done to the cochlea while introducing the implant," says Dr Kirtane.

Cost Prohibitive

Among the hurdles obstructing the usage of CI in India, the biggest one is the exorbitant cost of the device which varies in the range of Rs five lakh to nine lakh. CIs available in India through few major international companies are available in the market at international prices. At the moment, the electrodes in the CI device are assembled by people with their hands through a microscope which is one of the reasons why implants are expensive. On the other hand, improvement in the electronic technology, the cost of the ongoing research and training programmes conducted by the manufacturing companies adds up into the cost of the implant.

Countries like the UK and Australia have state-funded implant programmes. In the US, insurance companies pay for the CI. However, in India where most of the medical care is self financed, the poor ones who are deaf have no choice. Eighty per cent of the deaf population in the world is in the less developed counties. With over one million children alone in India requiring this, and with only 3,000 implants being conducted, it is a proof that the prohibitive cost is keeping the people away," shares Dr Mathew.

However, now there has come a ray of hope with State Government of AP coming up with a state-funded scheme to donate CI free-of-cost in the state.

sonal.shukla@expressindia.com