Flat Electrode Contacts for Peripheral Nerve Stimulation
The majority of available systems for nerve stimulation use circumferential stimulation electrodes inside an insulating cuff, which produce largely uniform current density within the nerve. Flat stimulation electrodes that contact only one side of the nerve may provide advantages including simpler implantation, ease of production, and more resistance to mechanical failure. However, it is possible that the flat configuration will yield inefficient fiber recruitment due to a less uniform current distribution within the nerve. Here we tested the hypothesis that flat electrodes will require higher current amplitude to achieve effective stimulation than circumferential designs. Computational modeling and in vivo experiments were performed to evaluate fiber recruitment in different nerves and different species using a variety of electrode designs. Initial results demonstrated similar fiber recruitment in the rat vagus and sciatic nerves with a standard circumferential cuff electrode and a cuff electrode modified to approximate a flat configuration. Follow up experiments comparing true flat electrodes to circumferential electrodes on the rabbit sciatic nerve confirmed that fiber recruitment was equivalent between the two designs. These findings demonstrate that flat electrodes represent a viable design for nerve stimulation that may provide advantages over the current circumferential designs for applications in which the goal is uniform activation of the nerve.