J Neurosci Res. 2020;00:1–15. wileyonlinelibrary.com/journal/jnr | 1 © 2020 Wiley Periodicals, LLC. Received: 24 September 2019 | Revised: 23 April 2020 | Accepted: 3 May 2020 DOI: 10.1002/jnr.24646 RESEARCH ARTICLE Localizing the seizure onset zone by comparing patient postictal hypoperfusion to healthy controls Tefani Perera 1,2 | Ismael Gaxiola-Valdez 1,2 | Shaily Singh 1,3 | Joseph Peedicail 1,3 | Sherry Sandy 3 | R. Marc Lebel 4,5 | Emmy Li 1,2 | Madison Milne-Ives 1,2 | Jessie Szostakiwskyj 2 | Paolo Federico 1,2,3,5 | on behalf of the Calgary Comprehensive Epilepsy Program collaborators Edited by Junie Warrington. Reviewed by Victoria Morgan and Thimmasettappa Thippeswamy. The peer review history for this article is available at https://publons.com/publon/10.1002/jnr.24646. Abbreviations: CBF, cerebral blood flow; pvcASL, postictal versus controls arterial spin labeling; sASL, subtraction arterial spin labeling; SOZ, seizure onset zone; TLE, temporal lobe epilepsy; VEEG, video-EEG. 1 Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada 2 Seaman Family MR Research Centre, University of Calgary, Calgary, AB, Canada 3 Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada 4 GE Healthcare, Calgary, Calgary, AB, Canada 5 Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada Correspondence Paolo Federico, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Room C1214a, Foothills Medical Centre, 1403 29th Street NW, Calgary, AB T2N 2T9, Canada. Email pfederic@ucalgary.ca Funding information Canadian Institutes of Health Research, Grant/Award Number: MOP-136839 Abstract Arterial spin labeling (ASL) MRI can provide seizure onset zone (SOZ) localizing infor- mation in up to 80% of patients. Clinical implementation of this technique is limited by the need to obtain two scans per patient: a postictal scan that is subtracted from an interictal scan. We aimed to determine whether it is possible to limit the number of ASL scans to one per patient by comparing patient postictal ASL scans to baseline scans of 100 healthy controls. Eighteen patients aged 20–55 years underwent ASL MRI <90 min after a seizure and during the interictal period. Each postictal cerebral blood flow (CBF) map was statistically compared to average baseline CBF maps from 100 healthy controls (pvcASL; patient postictal CBF vs. control baseline CBF). The pvcASL maps were compared to subtraction ASL maps (sASL; patient baseline CBF minus patient postictal CBF). Postictal CBF reductions from pvcASL and sASL maps were seen in 17 of 18 (94.4%) and 14 of 18 (77.8%) patients, respectively. Maximal postictal hypoperfusion seen in pvcASL and sASL maps was concordant with the SOZ in 10 of 17 (59%) and 12 of 14 (86%) patients, respectively. In seven patients, both pvcASL and sASL maps showed similar results. In two patients, sASL showed no significant hypoperfusion, while pvcASL showed significant hypoperfusion con- cordant with the SOZ. We conclude that pvcASL is clinically useful and although it may have a lower overall concordance rate than sASL, pvcASL does provide local- izing or lateralizing information for specific cases that would be otherwise missed through sASL. KEYWORDS arterial spin labeling, drug-resistant epilepsy, hypoperfusion, seizure onset zone