Clinical trial: cochlear implantation of adults with asymmetric hearing loss


A focus of research in the laboratory of Jill Firszt, PhD, is the study of asymmetric hearing loss, where patients have notable hearing differences between the ears. For example, when one ear has moderate hearing loss and one ear has profound hearing loss, a hearing aid for the poor ear has limited benefit. Consequently, these individuals must listen with only one ear.

Loss of binaural hearing results in decreased speech understanding and poor sound localization and has a substantial impact on daily communication and quality of life. The only available treatment that can provide hearing to the poor ear is a cochlear implant. Cochlear implantation of the poor ear is not routinely considered because current candidacy criteria include severe to profound hearing loss in both ears.

$2.25M grant for clinical trial

Dr. Firszt’s lab has received a four-year, $2.25 million grant supported by the National Institutes of Health (NIH) to conduct a clinical trial of cochlear implantation in adults with asymmetric hearing loss. The study, approved by the FDA, will evaluate the effects of treatment to the poor ear with a cochlear implant. A second goal is to assess whether bilateral input from a cochlear implant in one ear and acoustic hearing in the other ear improves speech understanding, sound localization, and quality of life. Quality of life measures address overall health, hearing handicap, and social and emotional consequences of hearing loss.

The study is currently running at four sites in the US: Washington University School of Medicine (lead site); House Ear Clinic, Los Angeles, CA; St. Luke’s Midwest Ear Institute, Kansas City, MO; and New York University, New York City, NY.

Dr. Firszt and her research team believe the results of the new study could profoundly influence the direction of clinical decisions and treatment for a substantial patient population who must rely on a unilateral signal that is degraded by hearing loss.

Figure (at right): Example audiograms (hearing tests) in panels A, B, C show hearing thresholds in the better ear and poor ear that meet the study inclusion criteria for individuals with asymmetric hearing. Frequency (pitch) is shown across the horizontal axis from 250 Hz (lowest) to 8000 Hz (highest). Intensity (volume) is shown along the vertical axis from -10 dB HL (very soft sound) to 120 dB HL (very loud sound). In panel A, the right ear is the poor ear; in panels B and C, the left ear is the poor ear. In panel C, the arrows shown off the X markings indicate that ear had no response to sound at the limits of the test equipment for each frequency tested. For all study participants, the poor ear receives a cochlear implant and the better ear continues to use a hearing aid.