Objective Measures of Cochlear Implant Electrode Position and Function

Cochlear implants (CIs) restore hearing to deaf patients by electrically stimulating the auditory nerve using an array of electrodes inserted into the cochlea (inner ear). All electrodes should be successfully inserted in the cochlea, with each electrode exciting a discrete range of auditory nerve fibers.

Our research investigates two exceptions to this ideal situation, both of which impair the participant's ability to clearly hear sounds such as speech. One exception occurs when some electrodes are located outside the cochlea, limiting the amount of information that is conveyed to the brain and potentially causing unwanted side effects.

Our research will identify these extra-cochlear electrodes during the CI operation, by stimulating each electrode in turn and recording from all other electrodes.

This "SCINSEV" technique then uses a sophisticated computational method to identify which if any electrodes are out of the cochlea. Even when all electrodes are in the cochlea, however, some may produce broad current spreads, which will "blur" the perception of sounds. Our second "PECAP" method measures these instances by stimulating pairs of electrodes and recording the neural responses. It also uses a new computational method, this time so as to calculate the neural spread from each electrode.

Both methods use fast, non-invasive, objective measurements that use the built-in capabilities of the implant .The interventions used are very similar to those employed in standard clinical practice, and the results will pave the way for better identification and management of poor hearing by CI patients