title: Ictal EEG source imaging in presurgical evaluation: High agreement between analysis methods.
abstract: OBJECTIVE
  To determine the agreement between five different methods of ictal EEG source imaging, and to assess their accuracy in presurgical evaluation of patients with focal epilepsy. It was hypothesized that high agreement between methods was associated with higher localization-accuracy.
  
  
  METHODS
  EEGs were recorded with a 64-electrode array. Thirty-eight seizures from 22 patients were analyzed using five different methods phase mapping, dipole fitting, CLARA, cortical-CLARA and minimum norm. Localization accuracy was determined at sub-lobar level. Reference standard was the final decision of the multidisciplinary epilepsy surgery team, and, for the operated patients, outcome one year after surgery.
  
  
  RESULTS
  Agreement between all methods was obtained in 13 patients (59%) and between all but one methods in additional six patients (27%). There was a trend for minimum norm being less accurate than phase mapping, but none of the comparisons reached significance. Source imaging in cases with agreement between all methods was not more accurate than in the other cases. Ictal source imaging achieved an accuracy of 73% (for operated patients: 86%).
  
  
  CONCLUSIONS
  There was good agreement between different methods of ictal source imaging. However, good inter-method agreement did not necessarily imply accurate source localization, since all methods faced the limitations of the inverse solution.
authors.affiliation: Department of Clinical Neurophysiology, Danish Epilepsy Centre, Dianalund, Denmark; Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark. Electronic address: sbz@filadelfia.dk.
authors.forename: Sándor
authors.initials: S
authors.lastname: Beniczky
authors.affiliation: Department of Clinical Neurophysiology, Danish Epilepsy Centre, Dianalund, Denmark; Sleep and Brain Plasticity Centre, Department of Neuroimaging, IOPPN, King's College and Imperial College, London, UK.
authors.forename: Ivana
authors.initials: I
authors.lastname: Rosenzweig
authors.affiliation: Research Department, BESA GmbH, Gräfelfing, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Scherg
authors.affiliation: Research Department, BESA GmbH, Gräfelfing, Germany.
authors.forename: Todor
authors.initials: T
authors.lastname: Jordanov
authors.affiliation: Research Department, BESA GmbH, Gräfelfing, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lanfer
authors.affiliation: Clinical Neurophysiology Unit, Department of Clinical Sciences, Lund University, Lund, Sweden; Electrical Geodesics, Inc., Eugene, OR, USA.
authors.forename: Göran
authors.initials: G
authors.lastname: Lantz
authors.affiliation: Clinical Neurophysiology Section, Department of Neurosurgery, Oslo University Hospital, Norway.
authors.forename: Pål Gunnar
authors.initials: PG
authors.lastname: Larsson
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004569:Electroencephalography; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D012640:Seizures / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000601:surgery; D055815:Young Adult
keywords: EEG; Epilepsy surgery; Inverse solution; Seizure; Source imaging