Middle Ear Implants Not Your Grandpa's Hearing Aid
By: Kathryn Clabo, CNN
August 22, 2002
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, 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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