title: Localizing seizure-onset zones in presurgical evaluation of drug-resistant epilepsy by electroencephalography/fMRI: effectiveness of alternative thresholding strategies.
abstract: OBJECTIVE
  Simultaneous EEG/fMRI is an effective noninvasive tool for identifying and localizing the SOZ in patients with focal epilepsy. In this study, we evaluated different thresholding strategies in EEG/fMRI for the assessment of hemodynamic responses to IEDs in the SOZ of drug-resistant epilepsy.
  
  
  METHODS
  Sixteen patients with focal epilepsy were examined by using simultaneous 92-channel EEG and BOLD fMRI. The temporal fluctuation of epileptiform signals on the EEG was extracted by independent component analysis to predict the hemodynamic responses to the IEDs. We applied 3 different threshold criteria to detect hemodynamic responses within the SOZ: 1) PA, 2) a fixed threshold at P < .05 corrected for multiple comparison (FWE), and 3) FAV (4000 ± 200 activated voxels within the brain).
  
  
  RESULTS
  PA identified the SOZ in 9 of 16 patients; FWE resulted in concordant BOLD signal correlates in 11 of 16, and FAV in 13 of 16 patients. Hemodynamic responses were detected within the resected areas in 5 (PA), 6 (FWE), and 8 (FAV) of 10 patients who remained seizure-free after surgery.
  
  
  CONCLUSIONS
  EEG/fMRI is a noninvasive tool for the presurgical work-up of patients with epilepsy, which can be performed during seizure-free periods and is complementary to the ictal electroclinical assessment. Our findings suggest that the effectiveness of EEG/fMRI in delineating the SOZ may be further improved by the additional use of alternative analysis strategies such as FAV.
authors.affiliation: Support Center of Advanced Neuroimaging, Inselspital, University of Bern, Switzerland. Martinus.Hauf@gmx.de
authors.forename: M
authors.initials: M
authors.lastname: Hauf
authors.forename: K
authors.initials: K
authors.lastname: Jann
authors.forename: K
authors.initials: K
authors.lastname: Schindler
authors.forename: O
authors.initials: O
authors.lastname: Scheidegger
authors.forename: K
authors.initials: K
authors.lastname: Meyer
authors.forename: C
authors.initials: C
authors.lastname: Rummel
authors.forename: L
authors.initials: L
authors.lastname: Mariani
authors.forename: T
authors.initials: T
authors.lastname: Koenig
authors.forename: R
authors.initials: R
authors.lastname: Wiest
mesh_terms: D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000627:therapeutic use; D001931:Brain Mapping / Q000379:methods*; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000175:diagnosis* / Q000503:physiopathology* / Q000628:therapy; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D017211:Treatment Failure; D055815:Young Adult
chemical_list: D000927:Anticonvulsants