title: Reproducibility of BOLD localization of interictal activity in patients with focal epilepsy: intrasession and intersession comparisons.
abstract: OBJECTIVE
  Simultaneous EEG-fMRI recordings allow the identification of haemodynamic changes induced by neuronal activity during ictal or interictal epileptiform events (IEDs). We evaluated the reproducibility of continuous EEG-fMRI (cEEG-fMRI) in patients with focal epilepsy.
  
  
  METHODS
  We studied 15 patients with focal epilepsy (8 cryptogenic and 7 symptomatic) and frequent interictal abnormalities. Each patient underwent two cEEG-fMRI acquisitions (runs) in the same day (session) and 8 patients repeated the examination after one month. cEEG-fMRI reproducibility was defined by the existence of partially overlapping clusters between activation maps obtained from different runs.
  
  
  RESULTS
  We detected IEDs in 40 out of 46 EEG-fMRI runs and a related significant BOLD-response in all 40 runs. A prevalent positive BOLD response was detected in 12 patients and a prevalent negative response in 3 subjects. Statistical maps included a mean of 10 significant clusters. Nearly 30% of clusters were reproducible in both intrasession and intersession comparisons, with a mean overlap of 30%. Reproducibility did not differ between positive and negative BOLD-responses.
  
  
  CONCLUSIONS
  Among the reproducible clusters, those with the highest percentage of overlap were concordant with the EEG electric field in all patients and they were localized in the same lobe as the brain lesion in patients with symptomatic epilepsy. We hypothesize that reproducible clusters could be more consistently related to the irritative zone than non-reproducible ones.
  
  
  CONCLUSIONS
  The evaluation of cluster reproducibility could improve our knowledge of IED-related BOLD response. Moreover, it could enhance the reliability of cEEG-fMRI to identify the irritative zone in focal epileptic patients.
authors.affiliation: Unit of Neuroradiology, AOUP Pisa, S. Chiara Hospital, via Roma 67, 56100, Pisa, Italy. ilariapesaresi@gmail.com
authors.forename: Ilaria
authors.initials: I
authors.lastname: Pesaresi
authors.forename: Mirco
authors.initials: M
authors.lastname: Cosottini
authors.forename: Gina
authors.initials: G
authors.lastname: Belmonte
authors.forename: Patrizia
authors.initials: P
authors.lastname: Maritato
authors.forename: Mario
authors.initials: M
authors.lastname: Mascalchi
authors.forename: Michele
authors.initials: M
authors.lastname: Puglioli
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Sartucci
authors.forename: Carlo
authors.initials: C
authors.lastname: Bartolozzi
authors.forename: Luigi
authors.initials: L
authors.lastname: Murri
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology; D001931:Brain Mapping / Q000379:methods; D004569:Electroencephalography / Q000379:methods*; D004828:Epilepsies, Partial / Q000097:blood / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood* / Q000378:metabolism*; D015203:Reproducibility of Results
chemical_list: D010100:Oxygen