News — The University of Miami’s Miller School of Medicine will be one of only three sites in the nation to test a potentially revolutionary opto-electrical cochlear implant, which could improve quality of life for millions with hearing loss.
Funded by a major multi-institutional grant from the National Institute on Deafness and Other Communication Disorders, the five-year study is being led by Claus-Peter Richter, M.D., Ph.D., vice chair for Research in the Department of Otolaryngology at Northwestern University. The UM arm is being led by Suhrud Rajguru, associate professor of Biomedical Engineering and Otolaryngology and co-director of the Institute for Neural Engineering, Jorge Bohorquez, Ph.D., associate professor of Biomedical Engineering and Michael Hoffer, M.D., professor of Otolaryngology.
Cochlear implants send electrical signals to the cochlear nerve to boost hearing. They are the world's most successful neuroprosthetic to date, restoring partial function in nearly 700,000 people, including congenitally deaf children, adults, and those who lose hearing from an infection or other causes.
Still, current implants utilizing electrical stimulation face limitations, making between 16-22 electrode contacts with the cochlea and providing only limited aural information. As a result, individual performance among recipients varies greatly; people with implants face difficulties enjoying music and often have trouble hearing conversation in loud rooms or noise.
“A normal cochlea transmits around 3,000 channels of information,” said Dr. Rajguru. “Current electrical implants replace that with somewhere between 16 and 22 channels only. It's remarkable the brain makes sense of it at all.”
The implant being studied uses light in the infrared range to stimulate the cochlea and could potentially encode far more acoustic information.
“The advantage of light is that it can be focused and confined in space like a laser pointer,” said Dr. Rajguru. “We hope to generate 50 to 100 channels or possibly more to provide increased spectral selectivity for encoding sound. These devices could better replicate the cochlea’s natural ability to transmit signals to the brain.”
“We have extensive experience restoring hearing for those with hearing loss using electrical implants. Now we have the potential to stimulate the hearing nerve in a more precise manner with light energy which can be directed to specific locations as opposed to the electrical current which spreads more broadly throughout the area,” said Fred F. Telischi, M.D., M.E.E., chairman of otolaryngology, professor of neurological surgery and biomedical engineering, and the James R. Chandler Chair in Otolaryngology. “This is a revolutionary breakthrough in cochlear implantation with the potential for substantial improvements in patients’ functional outcomes.”
This study is built on decades of research. Neuroscientists have long used light to stimulate neurons and trace brain circuits. In addition, prior to joining the Miller School, Dr. Rajguru was a postdoctoral researcher in Dr. Richter’s laboratory at Northwestern. This experience, and the Miller School’s overall research and clinical capabilities, made the University of Miami an ideal site for the study.
Trial participants will come from a small pool of people who have large tumors at the base of their skull, requiring translabyrinthine craniotomies to remove them. Unfortunately, this procedure damages the inner ear.
Still, the procedure does provide a unique opportunity to test optical stimulation in cochleae. It will be the first time this technology is tested in people.
“We are not yet approved to permanently implant the device and we have to proceed cautiously,” said Dr. Rajguru. “We hope that this study will allow us to go back to the FDA with the data and move forward with clinical translation.”
In addition to cochlear devices, Dr. Rajguru is also investigating the optical approach to modulate the vestibular system, the inner ear organs that govern spatial orientation. His lab is working on implants that could help patients dealing with vertigo, balance disorders and chronic dizziness.
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