title: Global and regional functional connectivity maps of neural oscillations in focal epilepsy.
abstract: Intractable focal epilepsy is a devastating disorder with profound effects on cognition and quality of life. Epilepsy surgery can lead to seizure freedom in patients with focal epilepsy; however, sometimes it fails due to an incomplete delineation of the epileptogenic zone. Brain networks in epilepsy can be studied with resting-state functional connectivity analysis, yet previous investigations using functional magnetic resonance imaging or electrocorticography have produced inconsistent results. Magnetoencephalography allows non-invasive whole-brain recordings, and can be used to study both long-range network disturbances in focal epilepsy and regional connectivity at the epileptogenic zone. In magnetoencephalography recordings from presurgical epilepsy patients, we examined: (i) global functional connectivity maps in patients versus controls; and (ii) regional functional connectivity maps at the region of resection, compared to the homotopic non-epileptogenic region in the contralateral hemisphere. Sixty-one patients were studied, including 30 with mesial temporal lobe epilepsy and 31 with focal neocortical epilepsy. Compared with a group of 31 controls, patients with epilepsy had decreased resting-state functional connectivity in widespread regions, including perisylvian, posterior temporo-parietal, and orbitofrontal cortices (P < 0.01, t-test). Decreased mean global connectivity was related to longer duration of epilepsy and higher frequency of consciousness-impairing seizures (P < 0.01, linear regression). Furthermore, patients with increased regional connectivity within the resection site (n = 24) were more likely to achieve seizure postoperative seizure freedom (87.5% with Engel I outcome) than those with neutral (n = 15, 64.3% seizure free) or decreased (n = 23, 47.8% seizure free) regional connectivity (P < 0.02, chi-square). Widespread global decreases in functional connectivity are observed in patients with focal epilepsy, and may reflect deleterious long-term effects of recurrent seizures. Furthermore, enhanced regional functional connectivity at the area of resection may help predict seizure outcome and aid surgical planning.
authors.affiliation: 1 UCSF Comprehensive Epilepsy Centre, University of California, San Francisco, California, USA 2 Department of Neurological Surgery, University of California, San Francisco, California, USA 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Dario J
authors.initials: DJ
authors.lastname: Englot
authors.affiliation: 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Leighton B
authors.initials: LB
authors.lastname: Hinkley
authors.affiliation: 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Naomi S
authors.initials: NS
authors.lastname: Kort
authors.affiliation: 1 UCSF Comprehensive Epilepsy Centre, University of California, San Francisco, California, USA 2 Department of Neurological Surgery, University of California, San Francisco, California, USA.
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Imber
authors.affiliation: 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Danielle
authors.initials: D
authors.lastname: Mizuiri
authors.affiliation: 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Susanne M
authors.initials: SM
authors.lastname: Honma
authors.affiliation: 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Findlay
authors.affiliation: 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Coleman
authors.initials: C
authors.lastname: Garrett
authors.affiliation: 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Paige L
authors.initials: PL
authors.lastname: Cheung
authors.affiliation: 1 UCSF Comprehensive Epilepsy Centre, University of California, San Francisco, California, USA 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Mantle
authors.affiliation: 1 UCSF Comprehensive Epilepsy Centre, University of California, San Francisco, California, USA 2 Department of Neurological Surgery, University of California, San Francisco, California, USA 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Phiroz E
authors.initials: PE
authors.lastname: Tarapore
authors.affiliation: 1 UCSF Comprehensive Epilepsy Centre, University of California, San Francisco, California, USA 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA 4 Department of Neurology, University of California, San Francisco, California, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Knowlton
authors.affiliation: 1 UCSF Comprehensive Epilepsy Centre, University of California, San Francisco, California, USA 2 Department of Neurological Surgery, University of California, San Francisco, California, USA 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Edward F
authors.initials: EF
authors.lastname: Chang
authors.affiliation: 1 UCSF Comprehensive Epilepsy Centre, University of California, San Francisco, California, USA 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA 4 Department of Neurology, University of California, San Francisco, California, USA Heidi.Kirsch@ucsf.edu.
authors.forename: Heidi E
authors.initials: HE
authors.lastname: Kirsch
authors.affiliation: 1 UCSF Comprehensive Epilepsy Centre, University of California, San Francisco, California, USA 3 Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
authors.forename: Srikantan S
authors.initials: SS
authors.lastname: Nagarajan
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000503:physiopathology*; D004567:Electrodes, Implanted; D004828:Epilepsies, Partial / Q000503:physiopathology / Q000628:therapy*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D016896:Treatment Outcome
keywords: epilepsy; functional connectivity; magnetoencephalography; outcome; surgery