Modeling the effects of electrode recessing on electrochemical safety in cochlear implant electrodes

Electrodes in neural prostheses may trigger stimulation-induced tissue damage if the magnitude of the stimulation exceeds safe levels. Consequently, the concentration of current densities at the periphery of planar electrodes has been studied extensively, and the use of electrode recesses has been suggested as a method of reducing such effects. Cochlear implant electrodes have significant geometrical differences from the planar electrodes used in earlier studies. We have previously used the finite element method to solve for current distributions on half-band cochlear implant electrodes. In this paper, we utilize similar models to investigate the effect of recessing half-band cochlear implant electrodes on their electrochemical safety. It was found that when recess depths were increased, the distribution of the electrodes became more uniform by up to 75.5%. The maximum reduction in irreversible faradaic reactions was found to be only 6.5% at the maximum recess depth, however other factors may contribute to the occurrence of irreversible faradaic reactions.