Intraoperative Cortico-Cortical Evoked Potential Monitoring for Tumor Resection in Eloquent Regions: A Systematic Review.

Preserving neurological function during brain tumor surgery near the eloquent cortex is a major challenge. Cortico-cortical evoked potentials (CCEPs) have emerged as a promising modality for intraoperative mapping of functional connectivity, especially in areas responsible for language, movement, and sensory integration. Unlike traditional motor or sensory evoked potentials, CCEPs allow assessment of bidirectional cortico-cortical pathways and have shown utility in epilepsy surgery. Their integration into tumor resections near eloquent areas remains a developing frontier. This systematic review aimed to evaluate the clinical utility, methodological consistency, and limitations of CCEP monitoring during brain tumor surgery involving eloquent regions. The systematic search of the literature occurred in PubMed, Scopus, Web of Science, and Google Scholar, with the search period between 2015 and 2024. Eight articles were deemed eligible for inclusion, presenting original data on the use of CCEP intraoperatively or more antecedently in surgical settings involving the eloquent cortex. The extraction was based on the demographic information of the patient, stimulation parameters, signal processing, and clinical response. The risk of bias was evaluated through ROBINS-I (Risk of Bias in Non-randomized Studies of Interventions). CCEPs were associated with improved mapping accuracy in six of eight studies and enabled enhanced visualization of cortico-cortical connectivity. Studies also highlighted variability in stimulation protocols and the influence of signal preprocessing. Only three studies showed a low overall risk of bias, reflecting heterogeneity in design and population. CCEP monitoring is a promising tool for functional mapping during tumor resection in the eloquent cortex. However, methodological inconsistencies and limited tumor-specific data highlight the need for standardized protocols and larger, prospective studies.