Breaking the walls of silence

By Nilika de Silva

Imagine a world without music, a world without sound.

Most of us take so much for granted. For in reality a considerable number of babies are born congenitally deaf, around the world. To their parents, the dreaded confirmation by the paediatrician would sound like a death knell.

But modern science has brought good news for any person with a hearing loss worse than 85 decibels. Being born deaf and dumb no longer means a life without sound and speech.

"Two percent of the world's population is congenitally deaf," said Audiologist R. Ranjith from the AVM, Madras ENT Research Foundation who is on a short, but fruitful visit to Sri Lanka. He is here to help children living in a world of silence, to hear the birds sing and the raindrops on the roof.

Ranjith who subscribes to the school of thought that sign language creates restrictions, said, "Through sign language you create another community." A graduate from Ramachandra Harvard Medical College, in Madras, this 24-year-old audiologist believes that congenital hearing loss cannot be cured by any medicine. And naturally if there is no hearing there is no speech. "If there is any problem in the middle or outer ear you can rectify it by surgery or medicine, but if the problem is in the inner ear there is no medicine. The only way is to manage with hearing aids. However, a hearing aid is nothing but an amplifier which helps both the listener and the speaker."

The function of the ear is to locate the sound and conduct it in the form of acoustical energy to the middle ear. Here the eardrum converts this acoustical energy to mechanical vibrations, which are carried by three bones in the middle ear. The third bone, the smallest in the body, is attached to the cochlea or inner ear.

Thirty years ago Professor William House embarked on research on cochlea implantation, in America. This was a revolutionary as it proved that even an affliction in the inner ear did not imprison one in a world of silence.

What Professor House figured out was that in the cycle of events that leads up to hearing loss if the inner ear was not functioning properly, an intervention could improve the situation. He operated on people with hearing loss, planted a receiver-stimulator behind the skin and made a hole in the cochlea and inserted a wire. The acoustical energy was thus converted to electrical energy and taken to a transmitting coil kept outside. This converted the electrical energy to radio frequency waves. The receiver stimulator absorbed it, converted it to electrical energy, stimulated the wire, which in turn stimulated the nerves and took it to the brain. This was the first invention known as the single channel implant, Mr. Ranjith said. The first implant was in 1974.

The next stage of development was by Prof. Graham Clerke, from the Melbourne Bionic Ear Institute, who read the characteristics of speech and employed a speech processor to analyse the incoming sound and pick up the speech sounds alone. This was the multi-channel implant. The internal equipment via a magnetic receiver-stimulator, had a powerful magnet. The transmitting coil also had a magnet.

Explaining the procedure involved in carrying out a cochlea implant, Mr. Ranjith said, "Doing the surgery is simple. Beyond surgery some type of rehabilitation is necessary. The rehabilitation is the most difficult and challenging part."

"Three weeks after surgery the patient comes to me. I have to fix the external equipment to the computer. I have to find the comfortable level of each and every electrode and each and every nerve, for the child. This is known as mapping procedure," he explained. "The child cries when he hears the first noise. The mother too will be crying out of happiness."

So far around 60,000 cochlea implants have been done around the world, the highest number being in Europe, mainly in Nottingham in Britain.

An implant on a child should be placed as early as possible. The earliest one in the world was on a six-month-old baby in South Africa.

In Sri Lanka, three such implants have been done on a 28-year-old man with acquired hearing loss due to a viral infection at the age of 26, an eight-year-old girl from Nawalapitiya and a two-year-old boy from Colombo.

Comprehensive testing is done to confirm that the person requires a cochlea implant. An audiometer, impedance meter, brain stem evoke response meter and Magnetic Resonance Imaging are used.

"The age of implantation is very important as children acquire speech very fast only up to five and a half years," he said. After this there will be a neural sheath, a lack of plasticity over the area responsible for speech and language acquisition, so that the acquisition of language is very slow. The moment you do a cochlea implant and switch on, the child is auditorily newborn.

There are two types of cochlea (implant) instruments - a 22-channel one costing Indian Rs. 385,000 and 24-channel one costing Indian Rs. 745,000.

Mr. Ranjith works for Dr. Mohan Kameshwaran, former Professor of the Royal College of Surgeons who started the Madras ENT Research Foundation. "My uncle Manoharan is also an audiologist. He was the audiologist at Madras Medical College and speech therapist for then Chief Minister M.G. Ramachandran who had had a paralytic attack and was unable to speak," he said.

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