[Electrophysiological Theory for Understanding Electrical Evoked Potential Monitoring]

Intraoperative neurophysiological monitoring(IOM)is a fundamental resource for complex neurosurgical procedures to prevent unpredictable neurological deficits and identify the exact location of a neurological function. IOMs have been classified based on evoked potential measurement by electrical stimulation. To understand the mechanism of an evoked potential, we must learn how the electric current is spread in humans. In this chapter, (1)electrical stimulation via stimulation electrode, (2)nerve depolarization by electric current stimulation, and(3)electric voltage gathered by a recording electrode have been described. Some of the contents in this chapter are presented in a perspective which might differ from that of a standard electrophysiological textbook. I hope the readers find their own interpretations on how electric current is spread in humans.