Intraoperative Neurophysiological Monitoring in Neuro-oncology

Neurosurgery can be considered a radical method to treat some illnesses and can seriously damage the nervous system. To avoid deleterious effects, such injuries must be detected during their initial development by means of intraoperative neurophysio‐ logical techniques (including intraoperative neurophysiological monitoring (IONM) and functional mapping). In this chapter, we review the most relevant and frequently performed IONM/mapping techniques. Some insight about the electrophysiological basis of stimulation and recording of the nervous system are provided. Intraoperative neurophysiological techniques can be divided into free running or evoked elicited. Among the first we discuss EMG, EEG and ECoG. Evoked potentials discussed include somato-sensory (SSEPs), auditory (BAEPs), visual (VEPs), motor (MEPs) and stimulated EMG. We are especially interested in the clear and concise exposition of the methodological peculiarities, the fields of application and the flaws associated with the different techniques discussed, with a focus on practical applications. Therefore, we show examples of real operations performed at our institution. We conclude that IONM and mapping are some of the techniques with more rele‐ vance during recent decades for oncological neurosurgery. The widespread use and improvement of these techniques have allowed a safer removal of a radical tumour, reducing the risk of permanent postoperative deficits and better functional postsurgi‐ cal outcomes during neuro-oncological surgery.