Electrophysiological recordings during orthopedic, neurological, and vascular surgery are gradually becoming part of standard medical practice, mainly because these procedures, unlike other intraoperative techniques such as X-ray and ultrasound imaging which provide information on the anatomical status of a structure, provide information regarding the functional integrity of the nervous system of a patient who, typically, is anesthetized and therefore cannot be neurologically examined. The value of these procedures, which are collectively known asintraoperative monitoring (IOM), stems from the fact that they are practical (no active patient participation is required), reliable (normal recordings are known to be very stable over time), and sensitive (they can promptly detect small changes in the activity of the nervous system).