Sedation may reduce reliability of MEG language mapping in pediatric epilepsy

A study published in Epilepsia examined whether sedation affects the physiological reliability of magnetoencephalography (MEG) language mapping in children with epilepsy. The analysis included 69 patients undergoing presurgical evaluation: 32 nonsedated and 37 sedated participants. Researchers measured auditory responses using the M200/M100 amplitude ratio and interhemispheric asymmetry, calculated language laterality indices from a continuous recognition memory task, and performed source localization using Fast-VESTAL.

Sedation preferentially suppressed late auditory responses, with a lower M200/M100 ratio (p < .001) and greater interindividual variability. Early sensory responses remained preserved, while auditory–language coupling was numerically attenuated. Low M200/M100 ratios frequently coincided with highly lateralized language indices, raising concern that seemingly decisive results could reflect reduced physiological reliability. Source imaging showed preserved primary auditory cortical activity but reduced recruitment of higher-order association networks in sedated participants.

The findings suggest that laterality indices should be interpreted alongside physiological response measures when planning epilepsy surgery in sedated children. The authors propose the M200/M100 ratio as a marker for identifying results requiring caution. However, the available abstract does not report a validated cutoff, diagnostic accuracy against an independent reference standard, or surgical outcomes. The observational comparison cannot establish that sedation alone explains the differences.