Stereo-electroencephalography is used to localize the seizure onset zone and connected neuronal networks in surgical candidates suffering from intractable focal epilepsy. The concept of an epileptogenicity index has been proposed recently to represent the likelihood of various regions being part of the seizure onset zone. It quantifies low-voltage fast activity, the electrophysiological signature of seizure onset usually assessed visually by neurologists. Here, we revisit epileptogenicity in light of neuroimaging tools such as those provided in statistical parametric mapping software. Our goal is to propose a robust approach, allowing easy exploration of patients' brains in time and space. The procedure is based upon statistical parametric mapping, which is an established framework for comparing multi-dimensional image data that allows one to correct for inherent multiple comparisons. Statistics can also be performed at the group level, between seizures in the same patient or between patients suffering from the same type of epilepsy using normalization of brains to a common anatomic atlas. Results are obtained from three case studies (insular reflex epilepsy, cryptogenic frontal epilepsy and lesional occipital epilepsy) where tailored resection was performed, and from a group of 10 patients suffering from mesial temporal lobe epilepsy. They illustrate the basics of the technique and demonstrate its very good reproducibility and specificity. Most importantly, the proposed approach to the quantification of the seizure onset zone allows one to summarize complex signals in terms of a time-series of statistical parametric maps that can support clinical decisions. Quantitative neuroimaging of stereo-electroencephalographic features of seizures might thus help to provide better pre-surgical assessment of patients undergoing resective surgery.

IMPORTANCE Cortical stimulation is used during presurgical epilepsy evaluation for functional mapping and for defining the cortical area responsible for seizure generation. Despite wide use of cortical stimulation, the association between cortical stimulation-induced seizures and surgical outcome remains unknown.OBJECTIVE To assess whether removal of the seizure-onset zone resulting from cortical stimulation is associated with a good surgical outcome.

SummaryObjectiveInterictal [18F]fluorodeoxyglucose–positron emission tomography (FDG‐PET) is used in the presurgical evaluation of patients with drug‐resistant focal epilepsy. We aimed at clarifying its relationships with ictal high‐frequency oscillations (iHFOs) shown to be a relevant marker of the seizure‐onset zone.MethodsWe studied the correlation between FDG‐PET and epileptogenicity maps in an unselected series of 37 successive patients having been explored with stereo‐electroencephalography (SEEG).ResultsAt the group level, we found a significant correlation between iHFOs and FDG‐PET interictal hypometabolism only in cases of temporal lobe epilepsy. This correlation was found with HFOs, and the same comparison between FDG‐PET and ictal SEEG power of lower frequencies during the same epochs did not show the same significance.SignificanceThis finding suggests that interictal FDG‐PET and ictal HFOs may share common underlying pathophysiologic mechanisms of ictogenesis in temporal lobe epilepsy, and combining both features may help to identify the seizure‐onset zone.