To find an alternative to the standard 50% threshold representation of estimated source localizations in epilepsy pre-surgical evaluation.

In epilepsy surgery, the focus can be difficult to ascertain. Source localization through non-invasive EEG can help. Currently, 50% thresholding of derived source spaces has become a de facto standard, but this can over/under-exaggerate the representation of source spaces.

Standard 50% thresholding yielded source spaces with median 19.2% individualized grey matter voxels, while “3-point thresholding” yielded median 26.2% voxels: p(W)=1.15690e-18. 3-point thresholding also harmonizes source estimation agreements between SWS in different foci groups: p(KW)=0.77355 unifocal, p(KW)=0.35049 multifocal. However, SWS affected 50% thresholded source spaces depending on foci location: multifocal p(KW)=0.00565, but not unifocal p(KW)=0.63884.

A novel customized “3-point threshold” yielded almost 1.5 times more source spaces for consideration and enhanced concordance of source space sizes between SWS, especially among multifocal patients. This is most helpful when standard 50% thresholding yields estimates that are too spatially restrictive or clinically incongruent where a robust alternative is needed.