|
A tiny, ultra-thin electrode placed directly in the auditory nerve is showing superior results to the standard cochlear implant, according to new research conducted at the University of Michigan Kresge Hearing Research Institute.
If the idea pans out in further animal and human studies, profoundly and severely deaf people would have another option that could allow them to hear low-pitched sounds common in speech, converse in a noisy room, identify high and low voices, and appreciate music — areas where cochlea implants, though a boon, have significant limitations.
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.
The process:
Researchers at the university used cats in the experiments, measuring brain processing of auditory signals in normal conditions. They then compared deaf animals’ brain responses to sounds using cochlear implants and then the direct auditory nerve implants. These measurements employed neuron-monitoring technology developed earlier at the university. The scientists found their sensitive 16-electrode microarray resulted in several advantages over cochlear implants.
If this initial success is borne out in further tests, a human auditory nerve implant is five to 10 years away, University of Michigan researcher John C. Middlebrooks said in a press release.
Improved approach:
Middlebrooks said that in nearly every measure, the new auditory nerve implants worked better than cochlear implants. Additionally, it’s possible the low power requirements of the auditory nerve implant might lead to a totally implantable device. Cochlear implant users must currently recharge batteries that power the device daily.
Approved by the Food and Drug Administration in 1984, cochlear implants have greatly benefited profoundly and severely deaf people. More than 100,000 implants have been performed worldwide in the last two decades, including more than 1,000 at the University of Michigan.
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. 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.
The future:
Middlebrooks has talked with surgeons in otolaryngology about surgical approaches in humans, and is working with U-M biomedical engineers on an intraneural device that can remain in place and be tested further in animals over the next two years. The devices need to be studied over time to see if they are safely tolerated by the auditory nerve.
Such a device might be used first in people whose cochleas are filled with bone and therefore aren’t eligible for a cochlear implant, or people whose cochlear implants are no longer effective.
The University of Michigan has submitted a patent application for the procedure. Through its Office of Technology Transfer, it is currently seeking a commercialization partner to assist in bringing the technology to market.
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.
|
