title: Epileptic networks in focal cortical dysplasia revealed using electroencephalography-functional magnetic resonance imaging.
abstract: OBJECTIVE
  Surgical treatment of focal epilepsy in patients with focal cortical dysplasia (FCD) is most successful if all epileptogenic tissue is resected. This may not be evident on structural magnetic resonance imaging (MRI), so intracranial electroencephalography (icEEG) is needed to delineate the seizure onset zone (SOZ). EEG-functional MRI (fMRI) can reveal interictal discharge (IED)-related hemodynamic changes in the irritative zone (IZ). We assessed the value of EEG-fMRI in patients with FCD-associated focal epilepsy by examining the relationship between IED-related hemodynamic changes, icEEG findings, and postoperative outcome.
  
  
  METHODS
  Twenty-three patients with FCD-associated focal epilepsy undergoing presurgical evaluation including icEEG underwent simultaneous EEG-fMRI at 3T. IED-related hemodynamic changes were modeled, and results were overlaid on coregistered T1-weighted MRI scans fused with computed tomography scans showing the intracranial electrodes. IED-related hemodynamic changes were compared with the SOZ on icEEG and postoperative outcome at 1 year.
  
  
  RESULTS
  Twelve of 23 patients had IEDs during recording, and 11 of 12 had significant IED-related hemodynamic changes. The fMRI results were concordant with the SOZ in 5 of 11 patients, all of whom had a solitary SOZ on icEEG. Four of 5 had >50% reduction in seizure frequency following resective surgery. The remaining 6 of 11 patients had widespread or discordant regions of IED-related fMRI signal change. Five of 6 had either a poor surgical outcome (<50% reduction in seizure frequency) or widespread SOZ precluding surgery.
  
  
  CONCLUSIONS
  Comparison of EEG-fMRI with icEEG suggests that EEG-fMRI may provide useful additional information about the SOZ in FCD. Widely distributed discordant regions of IED-related hemodynamic change appear to be associated with a widespread SOZ and poor postsurgical outcome.
authors.affiliation: Department of Clinical and Experimental Epilepsy, University College London Institute of Neurology, London, United Kingdom.
authors.forename: Rachel
authors.initials: R
authors.lastname: Thornton
authors.forename: Serge
authors.initials: S
authors.lastname: Vulliemoz
authors.forename: Roman
authors.initials: R
authors.lastname: Rodionov
authors.forename: David W
authors.initials: DW
authors.lastname: Carmichael
authors.forename: Umair J
authors.initials: UJ
authors.lastname: Chaudhary
authors.forename: Beate
authors.initials: B
authors.lastname: Diehl
authors.forename: Helmut
authors.initials: H
authors.lastname: Laufs
authors.forename: Christian
authors.initials: C
authors.lastname: Vollmar
authors.forename: Andrew W
authors.initials: AW
authors.lastname: McEvoy
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Walker
authors.forename: Fabrice
authors.initials: F
authors.lastname: Bartolomei
authors.forename: Maxime
authors.initials: M
authors.lastname: Guye
authors.forename: Patrick
authors.initials: P
authors.lastname: Chauvel
authors.forename: John S
authors.initials: JS
authors.lastname: Duncan
authors.forename: Louis
authors.initials: L
authors.lastname: Lemieux
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology* / Q000503:physiopathology*; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D054220:Malformations of Cortical Development / Q000150:complications* / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology / Q000503:physiopathology; D010351:Patient Discharge / Q000592:standards; D011184:Postoperative Period; D057234:Preoperative Period; D016896:Treatment Outcome