title: Spatial correlation of hemodynamic changes related to interictal epileptic discharges with electric and magnetic source imaging.
abstract: BACKGROUND
  Blood oxygenation level-dependent (BOLD) signal changes at the time of interictal epileptic discharges (IEDs) identify their associated vascular/hemodynamic responses. BOLD activations and deactivations can be found within the epileptogenic zone but also at a distance. Source imaging identifies electric (ESI) and magnetic (MSI) sources of IEDs, with the advantage of a higher temporal resolution. Therefore, the objective of our study was to evaluate the spatial concordance between ESI/MSI and BOLD responses for similar IEDs.
  
  
  METHODS
  Twenty-one patients with similar IEDs in simultaneous electroencephalogram/functional magnetic resonance imaging (EEG/fMRI) and in simultaneous EEG/magnetoencephalogram (MEG) recordings were studied. IEDs in EEG/fMRI acquisition were analyzed in an event-related paradigm within a general linear model (GLM). ESI/MSI of averaged IEDs was performed using the Maximum Entropy on the Mean. We assessed the spatial concordance between ESI/MSI and clusters of BOLD activations/deactivations with surface-based metrics.
  
  
  RESULTS
  ESI/MSI were concordant with one BOLD cluster for 20/21 patients (concordance with activation: 14/21 patients, deactivation: 6/21 patients, no concordance: 1/21 patients; concordance with MSI only: 3/21, ESI only: 2/21). These BOLD clusters exhibited in 19/20 cases the most significant voxel. BOLD clusters that were spatially concordant with ESI/MSI were concordant with IEDs from invasive recordings in 8/11 patients (activations: 5/8, deactivations: 3/8).
  
  
  CONCLUSIONS
  As the results of BOLD, ESI and MSI are often concordant, they reinforce our confidence in all of them. ESI and MSI confirm the most significant BOLD cluster within BOLD maps, emphasizing the importance of these clusters for the definition of the epileptic focus.
authors.affiliation: Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Canada.
authors.forename: Marcel
authors.initials: M
authors.lastname: Heers
authors.forename: Tanguy
authors.initials: T
authors.lastname: Hedrich
authors.forename: Dongmei
authors.initials: D
authors.lastname: An
authors.forename: François
authors.initials: F
authors.lastname: Dubeau
authors.forename: Jean
authors.initials: J
authors.lastname: Gotman
authors.forename: Christophe
authors.initials: C
authors.lastname: Grova
authors.forename: Eliane
authors.initials: E
authors.lastname: Kobayashi
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000503:physiopathology*; D001931:Brain Mapping / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods*; D004828:Epilepsies, Partial / Q000188:drug therapy / Q000503:physiopathology*; D006439:Hemodynamics; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015225:Magnetoencephalography / Q000379:methods*; D010100:Oxygen / Q000097:blood; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: EEG-functional magnetic resonance imaging (EEG/fMRI); electric source imaging; electroencephalogram (EEG); focal epilepsy; intracranial EEG; magnetic source imaging; magnetoencephalogram (MEG)