Intraoperative Monitoring of Central Neurophysiology

This chapter covers neurophysiological intraoperative monitoring (NIOM). It describes the relevant neurophysiological signals, their anatomical sources, the techniques used to record them, the manner in which they are assessed, and possible causes of intraoperative signal changes. Techniques used include electroencephalography (EEG), electromyography, and auditory, somatosensory, and motor evoked potentials. Some of these techniques can be used to localize and identify areas of cerebral cortex or the corticospinal tract. Recording of the electromyogram generated by reflex activity can be used to evaluate central nervous system function in some circumstances. EEG can be used to assess depth of anesthesia. Signals can be affected by anesthesia, and the chapter discusses various anesthetic agents, their effects on signals, and considerations for anesthetic management during NIOM. Personnel performing NIOM must be knowledgeable about the anatomy and physiology underlying the signals, the technology used to record them, and the factors (including anesthesia) that can affect them.