For almost 30 years, cochlear implants have been helping profoundly deaf patients around the world to hear and understand speech, revolutionising their lives and their wellbeing. Set against that success story is the experience of 15 to 20% of patients, who find the implant ineffective, with speech, music and other sounds horribly distorted and background noise overwhelming. Even the best implant performance does not deliver anywhere close to ‘normal’ hearing.

Professor Manohar Bance of the University of Cambridge and Honorary Consultant at Addenbrooke’s Hospital, has set out to investigate the detailed causes of these problems and how improved implants might be developed. With funding from the Evelyn Trust and a unique integrated team of talented clinicians, engineers and physiologists, the three-year research project began at the end of 2018.

“There are a couple of fundamental problems with the current types of implant. One is that because the fluid in the inner ear is conductive, the electrodes that deliver the signals to the nerves are spreading current throughout the cochlea and this is causing serious distortion. Also, in a patient with normal hearing, the nerves are tuned in different areas to certain parts of the sound spectrum and it’s not been possible to replicate that with the existing implants. Some patients also have nerve damage in the ear which can also be a barrier to the efficacy of the implant,” explains Manohar.

Working with engineers from the George Malliaras and Shery Huang labs at the University of Cambridge, the team has started by building plastic and other 3D printed models to measure electrical current spreads and voltage distribution inside the inner ear. They are also using cadaveric heads as the best possible way to understand exactly how the implant works in the human ear. Early results are very encouraging and already Professor Bance’s team has produced data about electrical current spread in the inner ear that has never before been available.

“Ultimately our research will inform the development of new designs of implants, incorporating new types of more focussed nerve stimulation that will help many more patients around the world to benefit from a cochlear implant. Improved cochlear implants cannot come too soon. There is a growing body of evidence that associates hearing loss with the progress of dementia. If we can reverse hearing loss, then we very significantly improve the quality of patients’ lives, reducing social isolation and associated mental health problems. But it’s also exciting to consider the possible impact of restored hearing on the progress of some types of degenerative brain disease. More research into these links is urgently needed.”

There’s more detail on Professor Bance’s work and other ground-breaking research projects at the  Cambridge Neuroscience website here: https://www.neuroscience.cam.ac.uk/directory/profile.php?Bance