A Two-Part Model for Determining the Electromagnetic and Physiologic Behavior of Cuff Electrode Nerve Stimulators

A two-part model for determining the electrophysiological behavior of a cuff electrode designed for unidirectional nerve stimulation is presented. In the first part, a model is described which evaluates the potential field of the cuff electrode system in the absence of a nerve. The model recognizes boundary conditions through the specification of secondary sources on the cuff; the unknown source strengths are found through the solution of a Fredholm integral equation. In the second part of the study, the potential field derived for the cuff is taken to be the applied field of a myelinated nerve fiber considered through a linear core-conductor model. The simulation confirms the existence of a "window" of the unidirectional stimulation, a condition that must exist to implement a collision block. The result corresponds to that obtained experimentally by van den Honert and Mortimer [11], [12], and suggests the applicability of such models to determine optimum cuff electrode designs.