Effect of anesthesia on electrocorticography for localization of epileptic focus: Literature review and future directions.

Intraoperative electrocorticography (ECoG) is a useful technique to guide resections in epilepsy surgery and is mostly performed under general anesthesia. In this systematic literature review, we seek to investigate the effect of anesthetic agents on the quality and reliability of ECoG for localization of the epileptic focus. We conducted a systematic search using PubMed and EMBASE until January 2019, aiming to review the effects of anesthesia on ECoG yield. Fifty-eight studies were included from 1016 reviewed. There are favorable reports for dexmedetomidine and remifentanil during ECoG recording. There is inadequate, or sometimes conflicting, evidence to support using enflurane, isoflurane, sevoflurane, and propofol. There is evidence to avoid halothane, nitrous oxide, etomidate, ketamine, thiopental, methohexital, midazolam, fentanyl, and alfentanil due to undesired effects. Depth of anesthesia, intraoperative awareness, and surgical outcomes were not consistently evaluated. Available studies provide helpful information about the effect of anesthesia on ECoG to localize the epileptic focus. The proper use of anesthetic agents and careful dose titration, and effective communication between the neurophysiologist and anesthesiologist based on ECoG activity are essential in optimizing recordings. Anesthesia is a crucial variate to consider in the design of studies investigating ECoG and related biomarkers.