Extra-operative somatosensory evoked potentials confirm the accuracy of MEG SEF localizations

Abstract

Abstract MEG somatosensory evoked fields (SEF) have been used in pre-surgical functional mapping to localize sensory cortex. Although the localization accuracy of the SEF has been compared to functional MRI, there have not been any direct comparisons between the SEF and sensory cortex identified by electrocorticography. In this retrospective study, we identified 9 children (5 males, 4 females; aged 4–17 yrs) who had pre-surgical functional mapping with MEG and then proceeded to epilepsy surgery with subdural grid recording. We compared the pre-operative localization of the MEG SEF with the location identified extra-operatively with subdural grid electrodes. We found 78% (7/9) concordance for gyral localization between pre-operative MEG and extra-operative grid recording. In the other two patients, MEG SEF was located in the central sulcus. We conclude that MEG demonstrates high accuracy in localizing sensory cortex and is a valuable tool in pre-surgical functional mapping.