Impact of sedation on the reliability of magnetoencephalographic language mapping in pediatric epilepsy

OBJECTIVE: Magnetoencephalography (MEG) language mapping in pediatric epilepsy frequently requires sedation, which may alter cortical physiology and compromise the reliability of language lateralization. We hypothesized that sedation disrupts coupling between early auditory processing and higher order language networks, reducing the interpretability of laterality metrics. METHODS: Sixty-nine pediatric patients undergoing presurgical MEG evaluation were analyzed, including 32 nonsedated and 37 sedated participants. Auditory evoked field responses were quantified using the M200/M100 amplitude ratio and interhemispheric asymmetry. Language laterality indices (LIs) were derived from a continuous recognition memory paradigm, and source localization was performed using Fast-VESTAL. RESULTS: Sedation preferentially suppressed late auditory responses, reflected by a significant reduction in the M200/M100 ratio (p < .001) and increased interindividual variability. Despite preserved early sensory responses, auditory-language coupling was numerically attenuated under sedation. Notably, low M200/M100 ratios were frequently associated with highly lateralized LI values, suggesting reduced physiological reliability and the potential for "false certainty" in language lateralization. Source imaging demonstrated preserved primary auditory cortical activity with reduced recruitment of higher order association networks in sedated participants. SIGNIFICANCE: Sedation compromises the physiological reliability of MEG language lateralization by disrupting late auditory and association-level processing. The M200/M100 ratio provides a practical physiological marker for identifying cases in which laterality results should be interpreted with caution. These findings support a physiology-informed framework for improving the clinical interpretation of MEG language mapping in sedated pediatric patients, with direct implications for presurgical planning in pediatric epilepsy.