Table 1.

Overview of the clinical features, presurgical investigations and surgical outcome of the 21 MRI-negative patients

Patient	Age at SEEG, years	Video-EEG	MEG	SEEG anatomy-based seizure-onset zone	Overlap MEG/ SEEG	Surgical procedure	Surgery outcome	Pathology
1	17	Left frontal	Focal	Left medial OFC, left lateral OFC lateral, left F3	Yes	Left lateral OFC, left F3	Engel I	FCDIIa
2	20	Right frontal	Lateralizing	Right posterior T2/right posterior T1/right superior parietal lobule, right inferior parietal lobule, right central	Yes	NA	NA	NA
3	12	Left front	No spike	Left pre-SMA, left medial F1, left lateral OFC 1	No spike	NA	NA	NA
4	36	Right front	Focal	Right T2, right T1, right temporal pole/right medial temporal lobe	Yes	Right temporal pole, right amygdala, right hippocampus, right T5	Engel I	Neuronal loss
5	4	Right front	Non lateralizing	Right lateral F1, right F2, right lateral OFC/right SMA	Yes	Right frontal deconnexion (F1-F2-pole), resection: right F3 resection and right OFC, anterior callosotomy	Engel IV	Mild MCD
6	24	Right frontal	Lateralizing	Right frontal pole, right medial F1	Yes	Right medial F1, right SMA, right frontal pole	Engel IV	Mild MCD
7	15	Left frontal	Non lateralizing	Left SMA, left pre-SMA, left lateral F2, left lateral F1, left lateral OFC, left posterior cingulate gyrus	Yes	Left frontal pole, left anterior F1, Left SMA, Left anterior cingulate gyrus	Engel III	Normal
8	55	Left frontal	Lateralizing	Left SMA, left pre-SMA/left F1, left F2	Yes	NA	NA	NA
9	19	Right temporal	Focal	Right lateral OFC	Yes	Right OFC	Engel I	Normal
10	36	Right temporal	Focal	Right OFC, right anterior T1, right anterior T2	Yes	Right OFC, right temporal pole, right amygdala, right hippocampus, right parahippocampus	Engel I	FCDI
11	32	Left frontal	Focal	Left frontal operculum, left precentral gyrus, left OFC	Yes	NA	NA	NA
12	11	Left frontal	Lateralizing	Left posterior cingulate gyrus, left medial parietal, left lateral parietal	Yes	NA	NA	NA
13	18	Left temporal-occipital	Lateralizing	Left basal temporal, left occipital, left parietal	Yes	NA	NA	NA
14	25	Left temporal	No spike	Left anterior medial temporal, left posterior medial temporal	No spike	NA	NA	NA
15	10	Right parietal/occipital	Lateralizing	Right superior parietal lobule, right inferior parietal lobule, right basal temporal	Yes	Right medial parietal, right posterior cingulate gyrus	Engel III	Normal
16	16	Left posterior perisylvian	Focal	Left posterior T1, left posterior T2, left posterior insula, left temporal pole	Yes	Left posterior T1, left posterior T2	Engel I	Normal
17	17	Left posterior perisylvian	Focal	Right temporo-parietal junction, right parietal operculum, right posterior insula	Yes	Right parietal operculum, right posterior T1, right posterior insula	Engel III	Normal
18	6	Left posterior perisylvian	Focal	Left frontal operculum, left parietal operculum	Yes	Left frontal operculum, left parietal operculum	Engel I	FCDIIa
19	25	Left frontal	No spike	Left temporal pole, left anterior T1/left anterior T2, left amygdala	No spike	NA	Engel III	Normal
20	8	Right central	No spike	Right medial parietal, right posterior central gyrus, right superior parietal lobule, right central	No spike	NA	NA	No
21	11	Left posterior perisylvian	Lateralizing	Left F1, left F2, frontal operculum, left temporal pole, left anterior insula, left posterior insula	Yes	NA	NA	NA

Video-EEG: the main lobar hypothesis regarding the location of the seizure-onset zone is provided; MEG: the extent of the MEG spiking volume determined by VIES is summarized in three categories (see ‘Material and methods’ section).

FCD = focal cortical dysplasia; F1 = superior frontal gyrus; F2 = middle frontal gyrus; F3 = inferior frontal gyrus; MCD = malformation of cortical development; NA = not applicable; OFC = orbito-frontal cortex; SMA = supplementary motor area; T1 = superior temporal gyrus; T2 = middle temporal gyrus; T5 = lingual gyrus.