COAXIAL INSULATED BIPOLAR ELECTRODE FOR MONOPOLAR AND BIPOLAR MAPPINGOF NEURAL TISSUE - TECHNICAL NOTE WITH EMPHASIS ON THE PRINCIPLES OF INTRAOPERATIVE STIMULATION

To facilitate use of various stimulation modes for intra-operative mon itoring during neurosurgical procedures, we designed and produced a va riable stimulation system that consists of a coaxial bipolar flush-tip insulated stimulation electrode, and a switch box to administer monop olar or bipolar stimulation through the same stimulation electrode. Th e electrode is composed of components that are readily available, so t hat its construction can be duplicated by others at minimal expense. F or mapping of neural tissue during surgical procedures, we use the mon opolar stimulation mode to identify relative large areas around the si te of stimulation which are free of motor nerve fibres. The bipolar st imulation mode is most useful for precise localization of motor nerve fibres and in distinguishing motor from non-motor fibres.