title: Electrical source imaging for presurgical focus localization in epilepsy patients with normal MRI.
abstract: OBJECTIVE
  Patients with magnetic resonance (MR)-negative focal epilepsy (MRN-E) have less favorable surgical outcomes (between 40% and 70%) compared to those in whom an MRI lesion guides the site of surgical intervention (60-90%). Patients with extratemporal MRN-E have the worst outcome (around 50% chance of seizure freedom). We studied whether electroencephalography (EEG) source imaging (ESI) of interictal epileptic activity can contribute to the identification of the epileptic focus in patients with normal MRI.
  
  
  METHODS
  We carried out ESI in 10 operated patients with nonlesional MRI and a postsurgical follow-up of at least 1 year. Five of the 10 patients had extratemporal lobe epilepsy. Evaluation comprised surface and intracranial EEG monitoring of ictal and interictal events, structural MRI, [(18)F]fluorodeoxyglucose positron emission tomography (FDG-PET), ictal and interictal perfusion single photon emission computed tomography (SPECT) scans. Eight of the 10 patients also underwent intracranial monitoring.
  
  
  RESULTS
  ESI correctly localized the epileptic focus within the resection margins in 8 of 10 patients, 9 of whom experienced favorable postsurgical outcomes.
  
  
  CONCLUSIONS
  The results highlight the diagnostic value of ESI and encourage broadening its application to patients with MRN-E. If the surface EEG contains fairly localized spikes, ESI contributes to the presurgical decision process.
authors.affiliation: Functional Brain Mapping Laboratory, 4 Rue Gabrielle-Perret-Gentil, Geneva, Switzerland. verena.brodbeck@unige.ch
authors.forename: Verena
authors.initials: V
authors.lastname: Brodbeck
authors.forename: Laurent
authors.initials: L
authors.lastname: Spinelli
authors.forename: Agustina M
authors.initials: AM
authors.lastname: Lascano
authors.forename: Claudio
authors.initials: C
authors.lastname: Pollo
authors.forename: Karl
authors.initials: K
authors.lastname: Schaller
authors.forename: Maria I
authors.initials: MI
authors.lastname: Vargas
authors.forename: Michael
authors.initials: M
authors.lastname: Wissmeyer
authors.forename: Christoph M
authors.initials: CM
authors.lastname: Michel
authors.forename: Margitta
authors.initials: M
authors.lastname: Seeck
mesh_terms: D000293:Adolescent; D000328:Adult; D038481:Anterior Temporal Lobectomy; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000503:physiopathology / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D004292:Dominance, Cerebral / Q000502:physiology; D004828:Epilepsies, Partial / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D055815:Young Adult