title: An assessment of MEG coherence imaging in the study of temporal lobe epilepsy.
abstract: OBJECTIVE
  This study examines whether magnetoencephalographic (MEG) coherence imaging is more sensitive than the standard single equivalent dipole (ECD) model in lateralizing the site of epileptogenicity in patients with drug-resistant temporal lobe epilepsy (TLE).
  
  
  METHODS
  An archival review of ECD MEG analyses of 30 presurgical patients with TLE was undertaken with data extracted subsequently for coherence analysis by a blinded reviewer for comparison of accuracy of lateralization. Postoperative outcome was assessed by Engel classification. MEG coherence images were generated from 10 min of spontaneous brain activity and compared to surgically resected brain areas outlined on each subject's magnetic resonance image (MRI). Coherence values were averaged independently for each hemisphere to ascertain the laterality of the epileptic network. Reliability between runs was established by calculating the correlation between epochs. Match rates compared the results of each of the two MEG analyses with optimal postoperative outcome.
  
  
  RESULTS
  The ECD method provided an overall match rate of 50% (13/16 cases) for Engel class I outcomes, with 37% (11/30 cases) found to be indeterminate (i.e., no spikes identified on MEG). Coherence analysis provided an overall match rate of 77% (20/26 cases). Of 19 cases without evidence of mesial temporal sclerosis, coherence analysis correctly lateralized the side of TLE in 11 cases (58%). Sensitivity of the ECD method was 41% (indeterminate cases included) and that of the coherence method 73%, with a positive predictive value of 70% for an Engel class Ia outcome. Intrasubject coherence imaging reliability was consistent from run-to-run (correlation > 0.90) using three 10-min epochs.
  
  
  CONCLUSIONS
  MEG coherence analysis has greater sensitivity than the ECD method for lateralizing TLE and demonstrates reliable stability from run-to-run. It, therefore, improves upon the capability of MEG in providing further information of use in clinical decision-making where the laterality of TLE is questioned.
authors.affiliation: Department of Neurosurgery, Henry Ford Health System, Detroit, Michigan, USA.
authors.forename: Kost
authors.initials: K
authors.lastname: Elisevich
authors.forename: Neetu
authors.initials: N
authors.lastname: Shukla
authors.forename: John E
authors.initials: JE
authors.lastname: Moran
authors.forename: Brien
authors.initials: B
authors.lastname: Smith
authors.forename: Lonni
authors.initials: L
authors.lastname: Schultz
authors.forename: Karen
authors.initials: K
authors.lastname: Mason
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Barkley
authors.forename: Norman
authors.initials: N
authors.lastname: Tepley
authors.forename: Valentina
authors.initials: V
authors.lastname: Gumenyuk
authors.forename: Susan M
authors.initials: SM
authors.lastname: Bowyer
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000592:standards*; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000592:standards*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D055815:Young Adult