title: Mesial temporal lobe epilepsy with hippocampal sclerosis is a network disorder with altered cortical hubs.
abstract: OBJECTIVE
  Electrophysiologic hubs within the large-scale functional networks in mesial temporal lobe epilepsy (mTLE) with hippocampal sclerosis (HS) have not been investigated. We hypothesized that mTLE with HS has different resting-state network hubs in their large-scale functional networks compared to the hubs in healthy controls (HC). We also hypothesized that the hippocampus would be a functional hub in mTLE patients with HS.
  
  
  METHODS
  Resting-state functional networks, identified by using magnetoencephalography (MEG) signals in the theta, alpha, beta, and gamma frequency bands, were evaluated. Networks in 44 mTLE patients with HS (left mTLE = 22; right mTLE = 22) were compared with those in 46 age-matched HC. We investigated betweenness centrality at the source-level MEG network.
  
  
  RESULTS
  The main network hubs were at the pole of the left superior temporal gyrus in the beta band, the pole of the left middle temporal gyrus in the beta and gamma bands, left hippocampus in the theta and alpha bands, and right posterior cingulate gyrus in all four frequency bands in mTLE patients; all of which were different from the main network hubs in HC. Only patients with left mTLE showed profound differences from HC at the left hippocampus in the alpha band.
  
  
  CONCLUSIONS
  Our analysis of resting-state MEG signals shows that altered electrophysiologic functional hubs in mTLE patients reflect pathophysiologic brain network reorganization. Because we detected network hubs in both hippocampal and extrahippocampal areas, it is probable that mTLE is a large-scale network disorder rather than a focal disorder. The hippocampus was a network hub in left mTLE but not in right mTLE patients, which may be due to intrinsic functional and structural asymmetries between left and right mTLE patients. The evaluation of cortical hubs, even in the spike-free resting-state, could be a clinical diagnostic marker of mTLE with HS.
authors: Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea.|Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea.
authors: Seung-Hyun
authors: SH
authors: Jin
authors: Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea.|Interdisciplinary Program in Neuroscience, Seoul National University College of Natural Science, Seoul, Korea.
authors: Woorim
authors: W
authors: Jeong
authors: Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea.|Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea.|Interdisciplinary Program in Neuroscience, Seoul National University College of Natural Science, Seoul, Korea.|Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.|Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea.
authors: Chun Kee
authors: CK
authors: Chung
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000473:pathology / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D008569:Memory Disorders / Q000209:etiology; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology*; D012146:Rest; D012598:Sclerosis / Q000209:etiology; D055815:Young Adult
keywords: Electrophysiologic cortical hubs; Hippocampal sclerosis; Large-scale functional network; Mesial temporal lobe epilepsy; Resting-state magnetoencephalography