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January 8, 2004

New device may reverse deafness

From: Sydney Morning Herald, Australia - Jan 8, 2004

Two deaf women have become the first in the world to have hearing devices implanted into their brain stems.

The risky procedure, using an Australian-made device, is designed to restore hearing in those who have no nerves connecting the ear to the brain.

Pioneer of the process Dr Bob Shannon, of the House Ear Institute in Los Angeles, said he would next week start testing the hearing of a 42-year-old woman, the second person to receive the implant.

"We just have to keep our fingers crossed," Dr Shannon said.

"We've been working on this for a long time and I hope it pays off and we can deliver good hearing for these people."

Results for the first patient, a 19-year-old woman, had been disappointing.

"She's not achieving the benefits we'd hoped for but it's a little too early to tell if she might improve," Dr Shannon said.

Both women had lost their auditory nerves during the surgical removal of brain tumours.

If the implants prove successful they could also work for children born without the nerves, but Dr Shannon warned against rushing to perform potentially hazardous brain surgery on young people.

"It takes many, many years of experience for your brain to understand and interpret the signals that are coming into the system so in a young child that's the best time to do that, but this is pretty difficult surgery which would normally only be used to remove a life-threatening tumour," he said.

"You'd have to weigh the risks and benefits of doing very difficult and dangerous surgery to give them this type of hearing which might be limited - we don't know yet."

At the moment, the only way to treat people without cochlear nerves is to implant a similar device that touches, but does not penetrate, the brainstem.

"The results with the surface electrode has not been as good as we'd hoped, and we think that the problem with the surface electrode is that it's not making good connection with the nerve in the brainstem," Dr Shannon said.

"The only way to make contact with that is to have micro-electrodes that penetrate in to contact those nerves."

Made by Australian bionic ear company Cochlear Ltd, the new device has eight electrodes of different lengths, which are inserted into the brainstem.

The electrodes will be able to stimulate several bundles of nerves individually to produce different sound frequencies.

"To understand speech and complex sounds you need to have different electrodes in different parts of those nerves so that we can selectively activate different pitches," Dr Shannon explained.

"If we can even get as many as four distinct pitch regions we think we can get people to the level of understanding speech.

"It could be something wonderful."


Copyright © 2004. The Sydney Morning Herald.