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| Implantable Hearing Aids Studied | |
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Two types of surgically implanted hearing aids now under study at Pittsburgh hospitals may help people with the most common type of hearing loss.
In contrast to conventional hearing aids, which amplify sounds that are then transmitted to the eardrum, the implantable devices are surgically emplaced in the middle ear, behind the eardrum. The hearing aids directly drive the bones of the middle ear, which transmit sound to the inner ear, or cochlea. The result, say developers, is less sound distortion, less feedback and less trouble with background noise.
Allegheny General Hospital is one of two U.S. centers testing the first fully implantable hearing aid, a model called the Envoy that is made by St. Croix Medical Inc. of Minneapolis. The eardrum serves as the hearing aid's microphone.
Last week, surgeons implanted the Envoy hearing aid in four patients. The systems won't be turned on, however, until the patients have healed, perhaps in six to eight weeks. Drs. Moises Arriaga and Douglas Chen are directing the study at AGH. About 10 patients will be enrolled.
UPMC Health System is one of 10 U.S. centers studying a semi-implanted model, called the Middle Ear Transducer, or MET, made by Otologics of Boulder, Colo. It has two parts: one that is surgically implanted in the middle ear and another that is a removable, external device. Unlike the Envoy, which uses the eardrum as its microphone, the MET relies on an external microphone that transmits sounds to the implant.
Dr. Barry Hirsch and audiologist Catherine Palmer lead the UPMC team, which has implanted one device thus far. That patient is still healing, so the device has not been activated.
Ninety patients will be enrolled by the 10 sites in the study.
Both types of devices are designed to help people with sensorineural hearing deficits, sometimes called nerve hearing loss, which typically occurs because of exposure to loud noises or such illnesses as measles or meningitis. It can also be hereditary. The hearing loss is caused by damaged or missing hair-like cells in the cochlea.
The implantable devices are supposed to reduce the distortion that can occur with external hearing aids, particularly when amplification must be high. The implants also may help people with hearing loss so severe that external aids are insufficient.
For information about the implantable hearing aid study at Allegheny General Hospital, call 877-284-2000. For information about the study at UPMC, call 412-647-2030.
Wednesday, March 20, 2002 By Byron Spice, Science Editor, Post-Gazette |
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