A comparison of electrophysiological measures for characterizing the cochlear-implant electrode-neuron interface.

The health of the auditory nerve is a key factor for hearing outcomes in cochlear-implant patients. Many electrophysiological markers of auditory-neural health have been proposed, with varying predictive power and independence from non-neural factors. The "Failure Index" (FI), the ratio between stimulation current level and response magnitude of the electrically-evoked compound action potential (eCAP) was compared to the Panoramic eCAP method. Both methods predicted localized areas of reduced neural responsiveness in a group of human cochlear-implant users, but the FI showed a greater dependence on a non-neural factor, namely, the distances between the cochlear-implant electrodes and the auditory nerves.