Intraoperative Corticocortical Evoked Potential Monitoring for Language Preservation during Glioblastoma Surgery under General Anesthesia

Objective: Intraoperative language mapping under general anesthesia plays an important role in brain tumor surgery, particularly when awake surgery cannot be performed. Corticocortical evoked potential (CCEP) monitoring is considered a valuable method for localizing functional language regions and evaluating neuronal connectivity. The present study aimed to assess the clinical usefulness of intraoperative CCEP monitoring in preserving language function during glioma surgery. Methods: A total of 18 consecutive patients with glioblastoma located in the left language-dominant hemisphere underwent CCEP-guided tumor resection under general anesthesia between January 2022 and December 2024. Subdural electrodes were positioned over the presumed anterior and posterior perisylvian language cortices, and bidirectional single-pulse CCEP stimulation was used to evaluate connectivity between these regions and to localize the arcuate fasciculus. The primary monitoring pathway was selected according to the most robust and stable CCEP response, and tumor resection was performed while preserving the mapped language network. Language function was assessed clinically before surgery, immediately after surgery, and again at 3-6 months after surgery using a 4-level ordinal scale. Results: Language-related CCEP monitoring was feasible in 15 of 18 patients. Among these, intraoperative CCEP signals remained stable in 9 patients, transiently decreased with recovery in 2 patients, and persistently decreased by the end of surgery in 4 patients. Unfavorable language outcomes were observed in 1 of 11 patients (9.1%) in the preserved/recovered group and in 1 of 4 patients (25.0%) in the persistent-decrease group. A single patient showed an unfavorable language outcome despite stable intraoperative CCEP findings. Conclusion: Intraoperative CCEP monitoring under general anesthesia may provide clinically useful information for language preservation during glioblastoma surgery when awake mapping is not feasible. Although further investigation is required to define a solid threshold for intraoperative CCEP deterioration, qualitative CCEP changes may be clinically informative and helpful in guiding surgical strategy.