• Isabell Ofer, Carmelina LeRose, Hansjoerg Mast, Pierre LeVan, Birgitta Metternich, Karl Egger, Horst Urbach, Andreas Schulze-Bonhage, and Kathrin Wagner.
• Epilepsy Center, Medical Center - Faculty of Medicine, University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany; Freiburg Brain Imaging Center, Medical Center - Faculty of Medicine, University of Freiburg, Germany. Electronic address: isabell.ofer@uniklinik-freiburg.de.
• Epilepsy Behav. 2019 Jan 1; 90: 238-246.

RationaleThe spontaneous synchronized activity and intrinsic organization of the Default Mode Network (DMN) has been found to be altered because of epileptic activity of temporal lobe origin. Thus, the aim of the present study was to compare DMN's topological properties in patients with seizure-free (SF) and not seizure-free (NSF) temporal lobe epilepsy (TLE).MethodsFunctional connectivity within the DMN was determined from an 8-minute resting state functional magnetic resonance imaging (fMRI) in 27 patients with TLE (12 SF, 15 NSF) and 15 healthy controls (HC). The DMN regions of interest were extracted according to the automated anatomical labeling (AAL) atlas. Network properties were assessed using standard graph-theoretical measures.ResultsAnalyses revealed, irrespectively of focus lateralization, borderline significance for longer paths (p = 0.049) and in trend reduced local efficiency within the DMN of SF when compared with that of NSF (p = 0.075). The SF and NSF patients did not differ in global network topology from HC (p > 0.05). At the nodal network level, the degree of central hubs was significantly reduced in SF when compared with that in NSF (0.002 ≤ p ≤ 0.080) and HC (0.001 ≤ p ≤ 0.066) while simultaneously, right anterior superior temporal gyrus revealed significantly higher degree in SF than in NSF (p = 0.005) and HC (p = 0.016).ConclusionSeizure freedom seems to be associated with hub redistributions that may underlie longer paths and (in trend) reduced local efficiency of the network. An associated slower system response might reduce the probability of a rapid spread of epileptic discharges over the whole network and may help to prevent hypersynchronous neuronal activity in brain networks that may result in epileptic seizures.Copyright © 2018 Elsevier Inc. All rights reserved.

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