Hybrid Cochlear Implants Blend High and Low Frequencies for a Fuller Sound

By Yishane Lee

“Electro-acoustic stimulation” is a mouthful, which may explain why “hybrid cochlear implant” is becoming shorthand for the latest thing in cochlear implantation.

What is a hybrid CI? It is a cochlear implant that makes use of residual hearing in the cochlea, with the goal of preserving it. Lina Reiss, Ph.D., of the Oregon Health and Science University, is a 2012 and 2013 Emerging Research Grant recipient conducting research in hybrid CIs, and she cowrote a piece in our Winter issue of Hearing Health introducing us to this exciting development.

The hybrid is especially promising because it is ideal for people with age-related hearing loss. As the story says:

“The hybrid CI helps people with high-frequency hearing loss while retaining their natural, residual hearing in the low frequencies. A high-frequency hearing loss, like that common in age-related hearing loss, makes consonants difficult to discern. The hybrid CI provides high-frequency information electrically and restores consonant perception. The residual low-frequency acoustic hearing helps ‘round out’ the artificial hearing provided by the CI, and together this gives the user a fuller hearing experience.”

Dr. Reiss collaborated with Christopher W. Turner, Ph.D., of the University of Iowa. Dr. Turner has been involved from the beginning in the development, assessment, and optimization of the hybrid electrode, with more than 20 publications on the subject since 2003, and he is a former HHF grant recipient as well.

One risk of hybrids is losing the low-frequency hearing entirely after implantation. A slightly longer electrode length—shorter than a traditional CI but longer than the initial hybrids—allows the implant to function like a traditional CI if the acoustic hearing is lost. It is undergoing clinical trials and received preliminary FDA approval last November, which is a very good sign.

I asked Dr. Reiss how she became a researcher, and specifically how she came to study cochlear implants. She says:

“I was always interested in science because my father was a scientist. In high school and college, I had some very stimulating research experiences in biological research. I also have a severe-profound hearing loss, and so have a personal interest in auditory research.

“After my sophomore year, I was lucky to obtain a summer research internship working in Eric Young’s auditory neurophysiology laboratory at Johns Hopkins University, where I studied how auditory nerve fibers encode speech sounds. I ended up doing my Ph.D. in that lab, studying how the dorsal cochlear nucleus encodes sound localization cues.

“However, I wanted to do more translational research, so ended up doing a postdoctoral fellowship with Chris Turner at the University of Iowa, where I got involved with the hybrid CI clinical trials. We got a lot of very interesting data with the hybrid CI study, particularly regarding brain plasticity, and there were many other interesting research directions to go on to from there.”

At HHF, we’re definitely excited to see where Dr. Reiss’s curiosity leads.

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