Chapter 15 - Intraoperative Neurophysiological Mapping and Monitoring for Supratentorial Procedures

Abstract

This chapter explores intraoperative neurophysiological mapping and monitoring for supratentorial procedures. The goal of delineation through mapping and monitoring of eloquent cortical areas and subcortical pathways is to achieve a more radical cytoreduction while still preserving unimpaired function. Somatosensory evoked potentials (SEPs) are typically elicited by the electrical bipolar stimulation of a peripheral nerve. The most commonly stimulated nerves are the median nerve, if sensory modalities and cortical regions representing the upper extremities are to be monitored, and the posterior tibial nerve for the lower extremities. SEP recording from these nerves is easiest to obtain and provides the most stable results. Neurophysiological mapping has corrected the presurgical estimation of the central sulcus location in 12% of patients. It also helps to identify the motor stimulation point for monitoring motor evoked potentials (MEPs). Intraoperative neurophysiological monitoring of the functional integrity of the cortical sensory and motor areas and pathways is noninvasive and does not interfere with the ongoing surgical procedure. It gives immediate feedback about functional impairment of the monitored structure. This provides the opportunity to rectify this impairment.