US Surgeons Explore Completely Implantable Hearing
Aids
Editor: We've been hearing about totally implantable hearing aids for
a while now, and they're finally here! They're still experimental, but
they are being implanted now. Some of the claims in the press release
may be a bit exaggerated - I'll need to see the evidence before I
believe some of it - but I do believe that implantable hearing aids hold
great promise.
March 2002 - Here's information on the Phase One
trial of Envoy Implantable System
from St. Croix Medical Inc.
September 2004 - And now, the Envoy is undergoing Phase
2 trials!
~~~~~~~~~~~~~~~~~~~
March 2002
A team of ear surgeons at Allegheny General Hospital (AGH) has become
the first in the United States to use a revolutionary, completely
implantable hearing restoration system that promises to greatly improve
the hearing capacity of those who suffer from mild to severe
sensorineural hearing deficits, the most common form of hearing loss -
associated with aging or exposure to loud noise.
An estimated 10 million of the 30 million Americans living with
sensorineural hearing loss would be considered good candidates for the
new therapy.
Pioneered by St. Croix Medical Inc., in Minneapolis, MN, the Envoy
Middle Ear Implantable System has been tested in Germany for the past
year and was just recently cleared by the Food and Drug Administration
for study in the U.S.
The Envoy technology is the only totally implantable hearing
restoration system in the world and AGH is one of two U.S. medical
centers that will investigate the technology in a phase one clinical
trial, joining the Virginia Mason Hearing for Life Center in Seattle,
Washington.
The investigation is being co-directed at AGH by nationally renowned
ear surgeons Moises Arriaga, M.D., and Douglas Chen, M.D., who are also
co-directors of the hospital's Hearing and Balance Center.
Last week, a 66-year-old North Side man became the first person in
the U.S. to receive the Envoy System, followed by three other patients,
a 73-year-old man from Wabash, a 58-year-old woman from Greensburg and a
63-year-old man from Johnstown. The systems will be activated for the
first time in approximately six to eight weeks after healing from the
surgical procedure.
According to Arriaga, excitement over the Envoy System centers around
its potential for both eliminating problems associated with
conventional, externally worn hearing aids, such as background noise,
acoustic feedback, ear canal occlusion and signal distortion, and its
application to a large number of people whose hearing loss threshold is
beyond the reach of current devices.
The potential for improved sound quality with the Envoy system
combined with the technology's invisibility could significantly increase
the number of people who seek assistance for their hearing loss, Arriaga
said. Currently, only 10-20 percent of those considered good candidates
for hearing aids use them.
"For most people who suffer from sensorineural hearing loss,
hearing aids can provide significant quality of life improvement. The
problem with conventional devices, however, is twofold; people often
don't like how they look or feel and the overall sound quality is fairly
limited. Additionally, for those whose hearing loss threshold is greater
than 55 decibels, conventional devices are typically ineffective,
leaving us with few therapeutic options," Arriaga said.
Conventional hearing aids conduct sound using directional microphones
that often pick up sound from sources other than what the user is
focused on, making it difficult to understand and interpret background
noise. In contrast, the Envoy System employs the body's own eardrum as
its microphone, using the natural acoustics of the ear canal without
obstruction, interference or any external devices. The input signals are
thus identical to those received by a person with normal hearing,
allowing for much better sound transmission and comprehension.
"The Envoy System clearly promises to take the field of hearing
restoration to a new level and its impact could be tremendous in terms
of the number of people with hearing loss who stand to benefit. The
advanced design and engineering of the technology should allow us in
most cases to return victims of sensorineural hearing loss to normal or
very close to normal hearing levels.
I believe it will become the standard by which all future hearing
restoration technology is based," said Chen.
Utilizing technology and components contained in implantable cardiac
pacemakers, the Envoy System employs state-of-the-art, biocompatible
piezoelectric transducers to detect and reproduce sound vibrations of
the middle ear bones. Two transducers, the Sensor and Driver, are
mounted to the middle ear bones and connected via fatigue-resistant
wires to a separate electronic unit implanted in the occipital bone
behind the ear that consists of a programmable sound processor and power
source.
The Sensor detects sound vibrations from the tympanic membrane
through the malleus and incus bones. The system converts those
vibrations into electrical signals that are amplified, filtered and
transmitted as mechanical vibrations through the Driver to the stapes
bone. The signal is then delivered via the stapes bone to the inner ear
where it is converted into nerve impulses and translated into words or
sound by the brain.
The Envoy System is powered by a pacemaker-type lithium battery with
a projected life-span of approximately five years. When the battery
begins to weaken, the implantable sound processor/power source can be
replaced independent of the more deeply implanted transducers, a
procedure that can be done on an outpatient basis under local
anesthesia.
The Envoy System's electronics circuit is programmable with radio
frequency telemetry and is comprised of bandpass amplifiers with
frequency responses controlled via physician or audiologist programming
to fit a patient's specific hearing loss profile. The system provides
adjustable gain and volume control, a configuration that allows the
hearing loss compensation for high frequency loss to be independent of
the compensation for low frequency loss. This compression feature
optimizes the device's function in changing environments, such as moving
from noisy situations to quiet situations.
Patients also have the ability to remotely program the implanted
system with a pocket sized programmer to adjust the volume, place the
unit in standby for sleep and select one of three programmed settings,
which have been individually tailored to the patient. Programmed
settings can be changed at any time by the audiologist or physician to
help patients adapt to the new sound or hearing performance changes.
Approximately 10 patients will be enrolled in the phase one study of
the Envoy System, with an expanded phase two study to commence shortly
after pending FDA approval, said Doug Hoag, spokesman for St. Croix.
~~~~~~~~~~~~~~~~~~~
September 2004
Editor: We've been following the story of the Envoy totally
implantable hearing aid for a couple of years now, and are excited to
see that they are in clinical trials. The technology (described towards
the end of the article) is pretty interesting. If any of our readers are
part of this trial, I'd love to hear your thoughts about this system.
~~~~~~~~~~~~~~~~~~~
From the newsroom of the Business Wire, Tuesday, September 7, 2004
St. Croix Medical, Inc. Announces Advancements in US and German
Pivotal Clinical Studies
Totally implantable Envoy(R) System restores quality of life in
patients with hearing loss
MINNEAPOLIS -- St. Croix Medical, Inc. (SCM) announced today that its
Envoy System has been implanted in several patients as part of the
product's pivotal clinical study. This study follows an earlier study
and will evaluate the safety and effectiveness of the company's device
in patients with sensorineural hearing loss on a larger scale.
Physicians in Greensboro, NC, Newport Beach, CA, Pittsburgh, PA and
Koblenz, Germany have performed the first procedures.
"The enrollment of these patients in the US and German clinical
trials is another step towards meeting the European and FDA requirements
for market approval," said Hans Neisz, SCM's President and Chief
Executive Officer. Neisz continued, "The preliminary results are
very encouraging and endorse the system's capabilities to provide
benefit to patients whose life is compromised or debilitated by their
hearing loss."
Over 21.5 million adults in the United States suffer from
sensorineural hearing loss. Conventional microphone-based hearing aids
are the most common treatment today for sensorineural hearing loss.
However, only 20 to 30% of the hearing impaired use hearing aids and
many who try hearing aids stop after a short period. The most commonly
sited limitations of hearing aids include poor understanding in noise,
poor sound quality, whistling (acoustic feedback), battery life, poor
fit and discomfort.
The technology platform of the Envoy System is different from all
other microphone-based hearing devices (hearing aids, other middle ear
implants or cochlear implants). The Envoy uses the eardrum to process
the incoming sound and thereby preserving a natural way of hearing that
particularly benefits patients in noisy environments.
Piezoelectric transducers sense minute mechanical vibrations at the
eardrum and convert them into electrical signals. These electrical
signals are then amplified and filtered by a "pacemaker-like"
sound processor and transmitted to a second piezoelectric transducer
that stimulates the inner ear naturally, and with significantly greater
efficiency than acoustic devices. The Envoy System is the only hearing
device that leverages the natural anatomical function of the ear and is
expected to result in better clarity of sound, better word recognition
and reduction of background noise. The proprietary microelectronics of
the Envoy consumes a very small amount of electrical current, allowing
the device to function for up to 4 years without maintenance. Being
totally implantable, the Envoy System is invisible to the onlooker and
eliminates the stigma that is often associated with hearing impairment.
SCM received an Investigational Device Exemption from the FDA, has
completed Phase I clinical trials and is now actively enrolling patients
to participate in the Phase II pivotal trial in both the United States
and Germany.
About SCM
SCM was founded in 1995 to design, develop and market implantable
devices for the treatment of sensory disorders. A privately held,
Minnesota-based company, the current focus of the organization is to
improve the quality of life for the millions of individuals suffering
from sensorineural hearing loss.
(c) Business Wire 2004
