Preservation of language function by mapping the arcuate fasciculus using intraoperative corticocortical evoked potential under general anesthesia in glioma surgery

OBJECTIVE Intraoperative language mapping under general anesthesia is imperative for brain tumor surgery because awake surgery is not always feasible. Monitoring corticocortical evoked potential (CCEP) is known to be a useful method for tracking neuronal connectivity and localizing functional areas. The authors evaluated the clinical benefit of intraopera- tive CCEP monitoring for language function preservation in patients undergoing glioma surgery.METHODS Between January 2019 and June 2021, the authors performed a total of 29 consecutive glioma surger-ies using CCEP monitoring under general anesthesia because of a risk of speech impairment; these were analyzed. Language area mapping was implemented by the anterior language area to posterior language area CCEP method for arcuate fasciculus mapping, and tumor resection was performed while avoiding the localized language areas. Language function before and after surgery was evaluated by the Controlled Oral Word Association Test (COWAT).RESULTS Intraoperative CCEP was successfully monitored in 25 patients (86.2%), and a valid signal was undetect-able in the other 4 patients. Language function evaluation was possible before and after surgery in a total of 20 patients. Overall, the preservation rate of language function was 65.0%, and the deterioration rate was 35.0% after tumor resec-tion with CCEP monitoring. Among those 8 patients with preoperative COWAT scores >= 18, 5 patients (62.5%) suc- cessfully preserved their language function, with COWAT scores > 18 after tumor resection. Among the 12 patients with preoperative deteriorated language function (COWAT score < 18), 8 patients (66.7%) showed improvement or preserved language function after surgery.CONCLUSIONS Intraoperative CCEP monitoring of the arcuate fasciculus is an acceptable technology for the preserva-tion of language function under general anesthesia in glioma surgery in patients in whom awake surgery is not feasible.