Investigators at the University of Michigan Kresge Hearing Research Institute believe that the latest model of auditory nerve implant, composed of an ultra-thin electrode array, can offer superior quality of sound to typical cochlear implants:
“In nearly every measure, these work better than cochlear implants,” says U-M researcher John C. Middlebrooks. He led a study requested by the National Institutes of Health to re-evaluate the potential of auditory nerve implants. Middlebrooks is a U-M Medical School professor of otolaryngology and biomedical engineering. He collaborated with Russell L. Snyder of the University of California, San Francisco and Utah State University. The two co-authored an article on the results in the June issue of Journal of the Association for Research in Otolaryngology.
The possible auditory nerve implants likely would be suitable for the same people who are candidates today for cochlear implants: the profoundly deaf, who can’t hear at all, and the severely deaf, whose hearing ability is greatly reduced. Also, the animal studies suggest that implantation of the devices has little impact on normal hearing, offering the possibility of restoring sensitivity to high frequencies while preserving remaining low-frequency hearing.
Middlebrooks says it’s possible that the low power requirements of the auditory nerve implants might lead to development of totally implantable devices. That would be an improvement over the external speech processor and battery pack cochlear implant users need to wear and often have to recharge daily.
If the initial success in animals is borne out in further tests, a human auditory nerve implant is probably five to 10 years away, he says…
Like the new device, cochlear implants are small electrode arrays that receive signals from an external sound processor… They are designed to stimulate the auditory nerve and other cells to produce a sensation of hearing. But their location, separated from auditory nerve fibers by fluid and a bony wall, is a limitation.
“Access to specific nerve fibers is blunted,” Middlebrooks says. “The effect is rather like talking to someone through a closed door.”
With the new intraneural stimulation procedure, that effect is eliminated, and there are other technical advantages, too. “The intimate contact of the array with the nerve fibers achieves more precise activation of fibers signaling specific frequencies, reduced electrical current requirements and dramatically reduced interference among electrodes when they are stimulated simultaneously,” Middlebrooks says.