title: Epilepsy surgery outcome and functional network alterations in longitudinal MEG: a minimum spanning tree analysis.
abstract: Seizure freedom after resective epilepsy surgery is not obtained in a substantial number of patients with medically intractable epilepsy. Functional neural network analysis is a promising technique for more accurate identification of the target areas for epilepsy surgery, but a better understanding of the correlations between changes in functional network organization due to surgery and postoperative seizure status is required. We explored these correlations in longitudinal magnetoencephalography (MEG) recordings of 20 lesional epilepsy patients. Resting-state MEG recordings were obtained at baseline (preoperatively; T0) and at 3-7 (T1) and 9-15months after resection (T2). We assessed frequency-specific functional connectivity and performed a minimum spanning tree (MST) network analysis. The MST captures the most important connections in the network. We found a significant positive correlation between functional connectivity in the lower alpha band and seizure frequency at T0, especially in regions where lesions were located. MST leaf fraction, a measure of integration of information in the network, was significantly increased between T0 and T2, only for the seizure-free patients. This is in line with previous work, which showed that lower functional network integration in lesional epilepsy patients is related to higher epilepsy burden. Finally, eccentricity and betweenness centrality, which are measures of hub-status, decreased between T0 and T2 in seizure free patients, also in regions that were anatomically close to resection cavities. Our results increase insight into functional network changes in successful epilepsy surgery and might eventually be utilized for optimization of neurosurgical approaches.
authors.affiliation: Department of Neurology, Cancer Center Amsterdam, VU University Medical Center, De Boelaan 1117, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands; Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, De Boelelaan 1118, P.O. Box 7057, Amsterdam, The Netherlands. Electronic address: E.vanDellen@vumc.nl.
authors.forename: Edwin
authors.initials: E
authors.lastname: van Dellen
authors.affiliation: Department of Neurology, Cancer Center Amsterdam, VU University Medical Center, De Boelaan 1117, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, 149 Thirteenth Street, Suite 2301, Charlestown, MA, USA; Harvard Medical School, Boston, MA, USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Douw
authors.affiliation: Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, De Boelelaan 1118, P.O. Box 7057, Amsterdam, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Hillebrand
authors.affiliation: Neurosurgical Center Amsterdam, VU University Medical Center, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands.
authors.forename: Philip C
authors.initials: PC
authors.lastname: de Witt Hamer
authors.affiliation: Neurosurgical Center Amsterdam, VU University Medical Center, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands.
authors.forename: Johannes C
authors.initials: JC
authors.lastname: Baayen
authors.affiliation: Department of Neurology, Cancer Center Amsterdam, VU University Medical Center, De Boelaan 1117, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Heimans
authors.affiliation: Department of Neurology, Cancer Center Amsterdam, VU University Medical Center, De Boelaan 1117, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands.
authors.forename: Jaap C
authors.initials: JC
authors.lastname: Reijneveld
authors.affiliation: Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, De Boelelaan 1118, P.O. Box 7057, Amsterdam, The Netherlands.
authors.forename: Cornelis J
authors.initials: CJ
authors.lastname: Stam
mesh_terms: D000328:Adult; D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D009415:Nerve Net / Q000503:physiopathology* / Q000601:surgery*; D017063:Outcome Assessment, Health Care / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: EZ; Functional connectivity; Glioma; Lesional epilepsy; MEG; MST; Magnetoencephalography; Minimum spanning tree; Network analysis; PLI; POS; Resective surgery; SF; epileptogenic zone; magnetoencephalography; minimum spanning tree; phase lag index; post-operative seizures; seizure free