Middle ear implants - an alternative to hearing aids
By: Roxane Tracey, July 21, 2000

The Symphonix implant simulates normal sound (Photo courtesy of Symphonix Inc.)

The world may soon sound a bit clearer for the hearing impaired. San Jose, California-based Symphonix, Inc.'s new surgical implant, the Vibrant Soundbridge may soon be sold as a treatment for people who suffer from moderate to severe hearing loss.

Although the surgical implant is not yet commercially available in the U.S., the device was recently recommended for approval by a panel of U.S. Food and Drug Administration advisers. The company believes that the recommendation will act as a stepping stone towards eventually providing a treatment for millions of hearing impaired adults that cannot be adequately treated with a conventional hearing aid.

Claudia Orellana, marketing manager for Symphonix, says that the mechanics of the Vibrant Soundbridge make it more effective than everyday hearing aids.

"A normal hearing aid works by producing an amplificational sound, so it's basically like a microphone and speaker that turn up volume inside the ear," says Orellana. "By contrast the Vibrant Soundbridge vibrates the bones in the middle ear in a mechanical way rather than just amplifying sound. So basically it mimics the way sound is naturally transmitted through the ear canal."

The Vibrant Soundbridge has both external and implantable components (Photo courtesy of Symphonix Inc.)

The Soundbridge does not sit in the inner ear like a hearing aid. Instead, sounds in the environment are picked up by the microphone located in the audio processor (the external part of the device). These sounds are then converted to an electrical signal within the audio processor and transmitted across the skin to an internal receiver. The signal is then sent by the conductor link - a wire leading to a small electromagnet, which in turn vibrates the tiny bones in the inner ear to produce sound.

Audiologist, Marshall Chasin, says that because the implant does not sit in the inner ear, it will give those who are hearing impaired the opportunity to avoid some of the complications associated with hearing aids.

"This will be advantageous to those who have hearing aids already and have not had optimal benefits from the devices," says Chasin, who is also the coordinator of research with the Canadian Hearing Society. "Problems with hearing aids can occur because they can produce whistling or feedback sounds."

Chasin added that Symphonix would also be beneficial for cosmetic reasons. "There are some who don't want anything to be seen in the ear canal. But the device is only partially implantable, so you will still need a little quarter-sized button for the battery, volume control and some of the electronics behind the ear and the hair."

But the implant surgery, which takes approximately three hours, is not without its risks, including facial and nerve damage, altered taste and temporary pain. Chasin says those who may be interested in the procedure should not be too concerned about the drawbacks.

"This is a well-known middle ear surgery," he says. "And there are nerves that can hang through the middle ear like the taste nerve and your facial nerve. But if your doctor sees any of those two nerves dangling in your middle ear he's going to close off the middle ear and say sorry I can't do the surgery."

According to Orellana, over 350 patients worldwide have had the device implanted, which is now commercially available in Europe. One of the patients who successfully received the middle ear treatment was Florida audiologist Lisa Evans-Smith whose testimonial is posted in the viewpoints section of Audiology Online's website. Evans-Smith, who was born with moderate-severe hearing loss, reports that she was frustrated with the discomfort of her hearing aid. In the testimonial she goes on to say that it was 'the best decision I have ever made concerning my hearing health.'

As of 1994, the total hearing impaired population was estimated at approximately 26 million, of which about 17 million people are classified as either moderately or severely hearing impaired.

For more information on Lisa Evans-Smith's middle ear implant check out Audiology Online 's website.

For more information on the Vibrant Soundbridge check out Symphonix Inc. 's website.

Copyright © 2953285 Canada Inc. cob Discovery Channel Canada 2000

You can see the original article at:
http://www.exn.ca/stories/2000/07/21/61.cfm
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