Chapter 12 - Electrophysiology and intraoperative neurophysiological monitoring

Abstract

Abstract The surgical treatment of tumours of the central nervous system has undergone significant changes due the technical advances of the past decade. Progress in functional assessment of the nervous system has been made that has influenced the efficacy of the surgical attempt of tumor removal. In particular, the advances of intraoperative neurophysiology contribute to the improvements of neurological outcome after neurosurgical procedures. Sudden changes of neurophysiological parameters may indicate surgically induced neurological impairment at times when a functional deficit is still reversible. Thus, the recent developments can provide that postoperatively the patients appear in optimal condition for nonsurgical oncological treatment. Methods of intraoperative neurophysiological mapping and monitoring have become an integral part of neuro-oncological surgery. Neurophysiological mapping installs the topography of functional neurogenic tissue in the operative field when a tumour is approached or the resection reaches adjacent functional areas. Neurophysiological monitoring provides continuous assessment of the activity or integrity of specific functional systems. The clinical applications of intraoperative neurophysiology mostly require a comprehensive understanding of the nervous system's functional integrity and demand multimodal sets of monitoring and mapping methods according to the anatomical location of the tumour. An essential requirement to maintain patients’ independence is the preservation of motor function. Recent advancements in the methodology of intraoperative neurophysiology can improve the preservation of motor function, through the introduction of motor evoked potentials in neurosurgery. The novel technique of motor evoked potential monitoring using transcranial electrical stimulation allows reliable assessment of the functional integrity of the corticospinal and corticobulbar tracts while the patient is under general anesthesia. Preservation of motor evoked potentials predicts the maintenance of voluntary control of limb movements and motor cranial nerve function. This chapter reports on the role of preoperative electrophysiology in neuro-oncology and summarizes theoretical and practical aspects of available neurophysiological methods used in the operating room based on references in the literature and personal experience.