Prototype middle-ear version of cochlear implant shows promise
MedWire News: Researchers hope that a miniature, middle-ear version of existing cochlear implants will revolutionize the technology for patients.
Cochlear implants have restored at least a basic level of hearing to over 200,000 deaf people since their development. However, recipients are currently required to wear a microphone and related electronics on the side of their head, which can be problematic.
"Imagine a child wearing a microphone behind the ear. It causes problems for a lot of activities. Swimming is the main issue. And it's not convenient to wear these things if they have to wear a helmet," said lead study author Darrin Young (University of Utah, Salt Lake City, USA) in a press statement.
He added that "for adults, it's social perception. Wearing this thing indicates you are somewhat handicapped and that actually prevents quite a percentage of candidates from getting the implant. They worry about the negative image."
Young and team have developed a middle-ear microphone device that they hope will significantly reduce the size of the external technology required for such devices, making them easier and more convenient for recipients than currently available cochlear implants.
The only significant external part of the new device would be a removable charger for the implanted battery, which recipients would need to wear at night.
"Everything is the same as a conventional cochlear implant, except we use an implantable microphone that uses the vibration of the bone," explained Young.
The prototype capacitive accelerometer-based device is about the size of an eraser on top of a pencil (2.5x6.2 mm) and weighs 25 mg. It has been successfully implanted and tested in the ear canals of four cadavers.
The device is currently capable of detecting a sound pressure level of 60 dB at 500 Hz, 35 dB at 2 kHz, and 57 dB at 8 kHz, but the researchers hope to improve this to 34 dB at 150 Hz and 24 dB at 500 Hz by using advanced microelectromechanical systems fabrication technology.
Improvement in the prototype is required before it is able to accurately detect normal conversational speech, particularly quieter, low-frequency sounds, says the team. They also hope to reduce the current size to approximately 2.0x2.0 mm. Therefore, Young and colleagues believe it will be at least 3 years before tests in people are carried out.
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By Helen Albert