Middle ear implants not your grandpa's hearing aid
http://www.cnn.com/2002/HEALTH/conditions/08/21/middle.ear.implants/index.html

By Kathryn Clabo
Special to CNN

(CNN) --Although 28 million Americans suffer from hearing loss, 80 percent of them shun hearing aids partly because, well, the devices don't have a reputation as the most attractive or comfortable or even effective accessory.

But a new generation of hearing devices -- called middle ear implants -- may help the hearing impaired while keeping embarrassment and irritation to a minimum.

The implants are made for people with sensorineural hearing loss ? a very common form of hearing loss that results from inner ear or nerve damage.

"Middle ear implants are a category of devices that are still fairly new and are used with a subgroup of people who have tried hearing aids and are dissatisfied," says Jaclyn Spitzer, professor of clinical audiology and speech pathology at Columbia Presbyterian Medical Center in New York.

The process of hearing starts when our ears turn sound waves into neural impulses. First, sound waves pass through the eardrum to the middle ear. There the sound waves cause bones called ossicles to vibrate, setting in motion a chain of events that eventually stimulates the auditory nerve to send impulses to the brain. The brain interprets the nerve impulses into different sounds. A breakdown at any step of this system can lead to hearing loss.

"People with the implants in a regular hearing test show a lot of functional gain," said Dr. Jose Fayad, director of cochlear and middle ear devices at Columbia Presbyterian Medical Center. "You have much better volume than with a hearing aid."

In general, middle ear implants are attached to the middle ear bones to enhance their vibration. This amplifies nerve impulses to the brain, increasing hearing ability. But all devices currently available also use an external component -- a small sound processor, much like a microphone, that usually is worn behind the ear.

The external device enhances the sound because it's "capable of being programmed" so small changes in hearing or listening can be adjusted, Spitzer said.

Two middle ear, implantable devices have been approved by the Food and Drug Administration for adult use. But only about 200 people in the U.S. and 500 in Europe have had them implanted ? often due to the expense of surgery. .

Some of the middle ear implants that are either FDA-approved or in the testing process include:

Vibrant Soundbridge (made by Symphonix): The Vibrant Soundbridge is approved by the FDA. It's an electromagnetic hearing device, meaning that it works by passing an electric current through a coil to create a magnetic field. This field causes a magnet on the ossicles to vibrate when hit by sound waves. The sound processor is worn behind the ear. The total cost for this device ? including surgery ? is about $15,000.

Direct Drive Hearing System (DDHS) P010023 (made by Soundtec, Inc.): This system is also FDA-approved. It uses a magnet placed deep inside the ear's canal to amplify sound. The DDHS has an external processor that fits behind the ear and looks much like a traditional hearing aid. This device costs around $5,000.

Middle Ear Transducer (MET) Ossicular Stimulator (Made by Otologics): The MET Ossicular Stimulator is in testing. About 100 study participants have had the device implanted so far.

Envoy Middle Ear Implantable System (St. Croix Medical, Inc.): The Envoy System is the first device that will not need an external processor, making it a fully implantable device. It is a piezoelectric device, meaning that an electric current is passed through a special crystal to produce a vibration on the eardrum. It uses the ear's own acoustics to amplify sound. The system is being tested at Allegheny General Hospital in Pittsburgh and Virginia Mason Medical Center in Seattle.
The devices have their share of converts. "Patients are happy," Columbia's Fayad said. "They say that they have clearer hearing. They hear better in everyday conditions, in real life, and they have much more comfortable hearing."

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