Study Fine-Tunes Hearing

From the Summer 2015 edition of Vanderbilt Medicine Magazine

Allyson, seated, and her audiologist, Rene Gifford, Ph.D., in the anechoic chamber, an echo-free room used for hearing research. Photo by John Russell.
Allyson, seated, and her audiologist, Rene Gifford, Ph.D., in the anechoic chamber, an echo-free room used for hearing research. Photo by John Russell.

When Vanderbilt audiologist Allyson Sisler-Dinwiddie, Au.D., received her own cochlear implant, she experienced what many such patients do – her hearing was restored, but understanding speech could be difficult, especially in noisy situations.

“There’s a wide range on how people do,” said David Haynes, M.D., professor of Otolaryngology, Neurosurgery and Hearing and Speech Sciences and director of the cochlear implant program.

Some do very well, while others return to audiologists dozens of times to have the device’s electrodes reprogrammed – between 12 and 22 of them – to improve hearing. Recognizing the need for improvement, an interdisciplinary research team at Vanderbilt came up with an innovative way to reprogram the implants. A Vanderbilt study showed that 72 percent of people participating preferred the new programming method over their previous program.

According to current clinical practice, all the electrodes in a cochlear implant are turned on and programmed, which sometimes causes interference when adjacent electrodes stimulate the same nerves, resulting in distortion or noise. The Vanderbilt team discovered that by turning certain electrodes off entirely, patients’ hearing often improved.

The study began in 2012, when the team developed a method of overlaying computer models of the auditory nerves onto patients’ CT scans to determine the location of the nerves. Once they could estimate where individual nerves were, they hypothesized that by turning off certain electrodes that stimulate the same groups of nerves, patients’ hearing might be improved.

Jack H. Noble, Ph.D., a research assistant professor in Electrical Engineering and Computer Science, created computer models of the cochlea that enable inferring the positions of the nerves in patient CT images. He did so using high-resolution imaging of 10 cadavers in his prior doctoral work.

“It’s a really exciting, new piece of information, and we’re excited to be able to explore how to use that information to help the programming process and improve outcomes,” he said.

Before Sisler-Dinwiddie participated in the study in 2012, the hearing in her right ear was more muffled than her left. “Anytime someone talked, it sounded like they had a mouth full of marshmallows,” she said.

The improvement in her right ear since reprogramming has been “unbelievable,” she said.

Rene Gifford, Ph.D., who is Sisler-Dinwiddie’s audiologist, recalls her calling on the phone, overjoyed about how she was hearing after her cochlear implants were reprogrammed.

“She said, ‘I don’t know what you did, but I can talk on the phone with this ear now,’” Gifford said. “I was blown away. I didn’t believe her.”

Though the method is only available at Vanderbilt now, the team hopes to make it more widely accessible. The study is the result of having an engineering school and a medical school right next to each other and the spirit of cooperation across campus, said Benoit Dawant, Ph.D., Cornelius Vanderbilt Professor of Engineering.

“The only place right now where this sort of method is being implemented is in the research lab here… across all of our labs,” Dawant said. “This type of research is probably possible at very few institutions and Vanderbilt is one of them.”

For more information about the study, contact Wendy Lipscomb at 615-936-2491 or wendy.lipscomb@vanderbilt.edu.