Regaining hearing thro’ a cochlear implant

We often see requests for donations to help people have cochlear implants, a procedure which enables the deaf to hear. The cost is high, around Rs. 2.5 million in Sri Lanka.

What exactly is a cochlear implant? MediScene spoke to Dr. Ravindra Ruberu and Dr. Mrs. Chandra Jayasuriya, Consultant ENT surgeons at the National Hospital, Sri Lanka to find out.

There are two processes in hearing. The human ear transmits the sound waves to the inner ear, the cochlea mechanically. This is the first process. The second is when the cochlea or the inner ear converts these waves into a nerve impulse and sends it to the brain via the auditory nerve.

When a person's hearing is impaired it could be due to a failure of either of the processes. When the hearing loss is severe, involving the cochlear function, the solution may be cochlear implantation. This is a prosthetic device which can convert the sound waves into an electrical impulse which ultimately stimulates the nerve and sends the signal to the brain. It sounds simple, but then why is the cost so high? This implant contains a platinum component and the technique used here is sophisticated. Thus the device is expensive, costing about Rs. 2.5 million.

However, this is not a panacea for all hearing problems. "We have to select the ideal candidates for the cochlear implants to gain good results," says Dr. Ravindra Ruberu, consultant ENT surgeon, at the National Hospital Sri Lanka, who is involved in cochlear implantation. It is indicated for people with severe hearing loss, where there is no benefit from the hearing aids. Congenitally deaf children and children whose hearing is impaired following meningitis form a major group of candidates.

However for congenitally deaf children the benefits of the procedure are better gained if it is performed at an early age, preferably before the age of two. Once the child grows older his brain wiring systems adapt to the way he is. Thus even if the surgery is done at a later age, his brain may not liaise with the new equipment. He may hear, but his brain does not know that he hears.

"This procedure does not miraculously restore a child with hearing impairment, to normal. This is just a first step in a rehabilitation process intended to help the child hear and speak," adds Dr. Ruberu, explaining that a vast amount of post-operative training has to be done for the child to 'learn to listen'.

"It's called auditory verbal therapy and we teach the child to recognize the sound and connect it with words," says speech therapist Ms. Jayamali Rupasinghe. This learning process has to go on for two to three years. Without auditory verbal therapy, a cochlear implant serves no purpose. How successful the child would be at picking up speech depends mainly on the learning abilities of the child and the motivation of the parents. "Parents may have to do auditory verbal therapy for their child for about five hours each day," added Ms. Rupasinghe, elaborating on the efforts necessary on the part of the parents.

Cochlear implants can serve adults who go deaf after having normal hearing, because their brains are adapted to hearing. The implantation gives better results if it is done following a short time of hearing impairment. The reason again is that the areas in the brain that recognize sound can shut off after years. It is not possible to make an adult talk by implanting a cochlea, if the person has never acquired speech skills.

In Sri Lanka, cochlear implantations are done only in the private sector. It is a major surgery taking about three hours. But it is not the facilities or the expertise that prevent this procedure being done in the government sector.

In the state sector, although we have trained ENT surgeons, speech therapists and the theatre facilities the government cannot afford Rs. 2.5 million rupees for each device, which of course only a few developed countries are doing. Still there is hope. "If the government can start a lottery like 'Govisetha' to support the poor children who need implants, then at least a few of them would be benefited," says Dr. Mrs. Jayasuriya.