title: Changes preceding interictal epileptic EEG abnormalities: comparison between EEG/fMRI and intracerebral EEG.
abstract: OBJECTIVE
  In simultaneous scalp electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), blood oxygen level dependent (BOLD) changes occurring before the spike have been sometimes described but could not be explained. To characterize the origin of this prespike BOLD signal change, we looked for electrographic changes in stereo-EEG (SEEG) possibly preceding the scalp spike in patients that showed early BOLD response in EEG/fMRI.
  
  
  METHODS
  We studied four patients with drug-resistant focal epilepsy who underwent EEG/fMRI, showed a prespike BOLD response, and were then studied with depth electrodes for presurgical localization of the epileptic generator. Early BOLD responses in the region of the spike field were analyzed using models with hemodynamic response functions (HRFs) peaking from -9 to +9 s around the spike. SEEG recordings in the period and location corresponding to the early HRF responses were analyzed to detect if electrographic changes were present in the SEEG before the scalp abnormality.
  
  
  RESULTS
  One of the four patients presented a SEEG interictal discharge in the period corresponding to the early BOLD response. In the other three, no electrographic changes were detected in the SEEG in the period corresponding to early BOLD changes.
  
  
  CONCLUSIONS
  Although the early BOLD activity may sometimes be explained by a synchronized neural discharge detectable with SEEG but not visible on the scalp EEG, in most cases the early BOLD response reflects a metabolic phenomenon that does not appear to result from a synchronized neuronal discharge. Prespike metabolic responses can result from synchronized or nonsynchronized neuronal activity, or from nonneuronal mechanisms including glia.
authors.affiliation: Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada. jean.gotman@mcgill.ca
authors.forename: Francesca
authors.initials: F
authors.lastname: Pittau
authors.forename: Pierre
authors.initials: P
authors.lastname: Levan
authors.forename: Friederike
authors.initials: F
authors.lastname: Moeller
authors.forename: Taha
authors.initials: T
authors.lastname: Gholipour
authors.forename: Claire
authors.initials: C
authors.lastname: Haegelen
authors.forename: Rina
authors.initials: R
authors.lastname: Zelmann
authors.forename: François
authors.initials: F
authors.lastname: Dubeau
authors.forename: Jean
authors.initials: J
authors.lastname: Gotman
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000378:metabolism* / Q000473:pathology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D004569:Electroencephalography / Q000379:methods*; D004828:Epilepsies, Partial / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D055815:Young Adult