Optimization of stimulus parameters for selective peripheral nerve stimulation with multi-contact electrodes

This study describes a method for optimizing selective stimulus parameters for multi-contact peripheral electrodes. Overlap between pairs of contacts is quantified by the deviation in their combined response from linear addition of their individual responses. Mathematical models are fit to recruitment and overlap data, and a cost function is defined to maximize recruitment and minimize overlap between all contacts. Results are presented for two four-contact nerve-cuff electrodes stimulating bilateral femoral nerves of one human subject with spinal cord injury. Knee extension moments between 11.6 and 17.2 Nm are achieved through two contacts of each nerve-cuff with less than 10% overlap between each pair of contacts. These results suggest that optimization can provide an automated means of determining stimulus parameters to achieve strong, selective muscle contractions through multi-contact peripheral nerve electrodes.