title: ICA extracts epileptic sources from fMRI in EEG-negative patients: a retrospective validation study.
abstract: Simultaneous EEG-fMRI has proven to be useful in localizing interictal epileptic activity. However, the applicability of traditional GLM-based analysis is limited as interictal spikes are often not seen on the EEG inside the scanner. Therefore, we aim at extracting epileptic activity purely from the fMRI time series using independent component analysis (ICA). To our knowledge, we show for the first time that ICA can find sources related to epileptic activity in patients where no interictal spikes were recorded in the EEG. The epileptic components were identified retrospectively based on the known localization of the ictal onset zone (IOZ). We demonstrate that the selected components truly correspond to epileptic activity, as sources extracted from patients resemble significantly better the IOZ than sources found in healthy controls. Furthermore, we show that the epileptic components in patients with and without spikes recorded inside the scanner resemble the IOZ in the same degree. We conclude that ICA of fMRI has the potential to extend the applicability of EEG-fMRI for presurgical evaluation in epilepsy.
authors.affiliation: STADIUS Center for Dynamical Systems, Signal Processing and Data Analytics, Department of Electrical Engineering (ESAT), KU Leuven, Leuven, Belgium ; iMinds Future Health Department, Leuven, Belgium.
authors.forename: Borbála
authors.initials: B
authors.lastname: Hunyadi
authors.forename: Simon
authors.initials: S
authors.lastname: Tousseyn
authors.forename: Bogdan
authors.initials: B
authors.lastname: Mijović
authors.forename: Patrick
authors.initials: P
authors.lastname: Dupont
authors.forename: Sabine
authors.initials: S
authors.lastname: Van Huffel
authors.forename: Wim
authors.initials: W
authors.lastname: Van Paesschen
authors.forename: Maarten
authors.initials: M
authors.lastname: De Vos
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004827:Epilepsy / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D055815:Young Adult