title: EEG and MEG source analysis of single and averaged interictal spikes reveals intrinsic epileptogenicity in focal cortical dysplasia.
abstract: OBJECTIVE
  Simultaneous interictal EEG and magnetoencephalography (MEG) recordings were used for noninvasive analysis of epileptogenicity in focal cortical dysplasia (FCD). The results of two different approach methods (multiple source analysis of averaged spikes and single dipole peak localization of single spikes) were compared with pre- and postoperative anatomic magnetic resonance imaging (MRI).
  
  
  METHODS
  We studied nine children and adolescents (age, 3.5-15.9 years) with localization-related epilepsy and FCD diagnosis based on MRI. Five patients underwent epilepsy surgery, two of them after long-term recording with subdural grid electrodes, and one after intraoperative electrocorticography.
  
  
  METHODS
  The 122-channel whole-head MEGs and 33-channel EEGs were recorded simultaneously for 25 to 40 min. Interictal spikes were identified visually and used as templates to search for similar spatiotemporal spike patterns throughout the recording. With the BESA program, similar spikes (r > 0.85) were detected, averaged, high-pass filtered (5 Hz) to enhance spike onset, and subjected to multiple spatiotemporal source analysis with a multishell spherical head model. Peak activity from single spikes was modeled by single dipoles for the same subset of spikes. Source localization was visualized by superposition on T1-weighted MRI and compared with the lesion identified in T1- and T2-weighted MRI. In the five cases undergoing epilepsy surgery, the results were correlated with invasive recordings, postoperative MRI, and outcome.
  
  
  RESULTS
  In all cases, the analysis of averaged spikes showed a localization of onset- and peak-related sources within the visible lesion for both EEG and MEG. Of the single spikes, 128 (45%; total 284) were localizable at the peak in MEG, and 170 (60%) in EEG. Of these, 91% localized within the lesion with MEG, and 93.5% with EEG. In three of five patients operated on, the resected area included the onset zones of averaged EEG and MEG spike activity. These patients had excellent postoperative outcome, whereas the others did not become seizure free.
  
  
  CONCLUSIONS
  Consistent MEG and EEG spike localization in the lesional zone confirmed the hypothesis of intrinsic epileptogenicity in FCD.
authors.affiliation: Department of Child Neurology, University of Heidelberg, Heidelberg, Germany. Thomas_Bast@med.uni-heidelberg.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Bast
authors.forename: Oezdin
authors.initials: O
authors.lastname: Oezkan
authors.forename: Sabine
authors.initials: S
authors.lastname: Rona
authors.forename: Christoph
authors.initials: C
authors.lastname: Stippich
authors.forename: Angelika
authors.initials: A
authors.lastname: Seitz
authors.forename: Andre
authors.initials: A
authors.lastname: Rupp
authors.forename: Susanne
authors.initials: S
authors.lastname: Fauser
authors.forename: Josef
authors.initials: J
authors.lastname: Zentner
authors.forename: Dietz
authors.initials: D
authors.lastname: Rating
authors.forename: Michael
authors.initials: M
authors.lastname: Scherg
mesh_terms: D002540:Cerebral Cortex / Q000002:abnormalities* / Q000503:physiopathology / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data*; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography / Q000379:methods / Q000706:statistics & numerical data*; D008297:Male; D009421:Nervous System Malformations / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D016896:Treatment Outcome