• Yuto Suzuki, Rei Enatsu, Aya Kanno, Rintaro Yokoyama, Hime Suzuki, Shunsuke Tachibana, Yukinori Akiyama, Takeshi Mikami, Satoko Ochi, Michiaki Yamakage, and Nobuhiro Mikuni.
• Department of Neurosurgery, Sapporo Medical University, Sapporo, Hokkaido, Japan.
• World Neurosurg. 2019 Mar 1; 123: e685-e692.

BackgroundPrevious studies have reported the usefulness of intraoperative corticocortical evoked potentials (CCEPs) for preserving language function during brain surgery.ObjectiveThis study aimed to assess the influence of depth of anesthesia on CCEP to establish its clinical utility.MethodsTwenty patients with brain tumors or epilepsy who underwent awake craniotomy were included in this study. Before resection, the electrode plates were placed on the frontal and temporoparietal cortices, and 1-Hz alternating electrical stimuli were delivered to the pars opercularis/pars triangularis in a bipolar fashion. Electrocorticograms from the temporoparietal cortices time-locked to stimuli were averaged to obtain CCEP responses from a state of deep anesthesia until the awake state. The correlation between CCEP waveforms and bispectral index (BIS) was evaluated.ResultsCCEP amplitude increased with the increase in the BIS level. CCEP latency decreased in 5 patients and increased in 15 patients under anesthesia compared with the awake state. CCEP amplitudes decreased by 11.3% to 75.2% (median 31.3%) under anesthesia with <65 BIS level. These differences were statistically significant (P < 0.01, Wilcoxon signed-rank test). With respect to CCEP latencies, there was no significant difference between the awake and anesthetic states.ConclusionsCCEP amplitudes were correlated with depth of anesthesia, whereas CCEP latencies were not affected by anesthesia. The influence of anesthesia should be considered when applying this technique to intraoperative monitoring.Copyright © 2018 Elsevier Inc. All rights reserved.

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