Drug-resistant epilepsy is a diagnostic and therapeutic challenge, mainly in patients with negative MRI findings. State-of-the-art imaging methods complement standard epilepsy protocols with new information and help epileptologists to increase the reliability of their decisions. In this study, we investigate whether arterial spin labeling (ASL) perfusion MRI can help localize the epileptogenic zone (EZ). To that end, we developed an image processing method to detect the EZ as an area with hypoperfusion relative to the contralateral unaffected side, using subject-specific thresholding of the asymmetry index in ASL images. We demonstrated three thresholding criteria (termed minimal product criterion, minimal distance criterion, and elbow criterion) on 29 patients with MRI-negative epilepsy (age 32.98 ± 10.4 years). The minimal product criterion showed optimal results in terms of positive predictive value (mean 0.12 in postoperative group and 0.22 in preoperative group) and true positive rate (mean 0.71 in postoperative group and 1.82 in preoperative group). Additionally, we found high accuracy in determining the EZ side (mean 0.86 in postoperative group and 0.73 in preoperative group out of 1.00). ASL can be easily incorporated into the standard presurgical MR protocol, and it provides an additional benefit in EZ localization.

CEITEC Central European Institute of Technology Neuroscience Center Masaryk University Brno Czech Republic

Department of Neurology Brno Epilepsy Center St Anne's University Hospital and Medical Faculty of Masaryk University Pekařská 53 Brno 656 91 Czech Republic

Department of Radiology and Nuclear Medicine Amsterdam University Medical Center VU University Medical Center Amsterdam Neuroscience Amsterdam The Netherlands

Department of Radiology and Nuclear Medicine University Hospital Ghent Ghent Belgium

Institute of Radiopharmaceutical Cancer Research Helmholtz Zentrum Dresden Rossendorf Dresden Germany

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