Cochlear Implant Aids the Profoundly Deaf

A team at the University of Michigan (Ann Arbor, MI, USA) made the implant and embedded thin-film electrode sites that directly stimulate the auditory nerve. The implant is currently being tested in guinea pigs and cats, said team leader Kensall D. Wise, director of the Center for Wireless Integrated Microsystems (WIMS, Ann Arbor, MI, USA), who also holds appointments in the departments of biomedical engineering, electrical engineering, and computer science at the university. The device may be available in four to five years for use in humans.

Approximately 100,000 patients to date have received cochlear implants worldwide. The current technology, Dr. Wise noted, is bulky, difficult for surgeons to insert, and does not allow a great range of perceived frequencies. The present implants use electrodes formed from a bundle of wires fed into the snail-shaped cochlea of the inner ear, and each implant has anywhere from 16 to 22 stimulating sites along its length. By contrast, the new implant will host up to 128 stimulating sites.

The range of frequencies that can be stimulated depends on how far into the cochlea the implant can go, with the lower frequencies located further up toward the apex of the spiral canal, said Dr. Wise. More sites mean greater tonal range and better frequency perception, and the implant's flexibility will minimize damage to existing hearing.

The ribbon film technology lets researchers embed other functions in the implant, such as position sensors that allow surgeons to watch the implant's progress on a monitor as they are feeding it into the cochlea. The implant can be manufactured by the same process used in making integrated circuits, which means it can be mass produced.



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