title: Scalp EEG does not predict hemispherectomy outcome.
abstract: BACKGROUND
  Functional hemispherectomy is effective in carefully selected patients, resulting in a reduction of seizure burden up to complete resolution, improvement of intellectual development, and developmental benefit despite possible additional neurological deficit. Despite apparent hemispheric pathology on brain magnetic resonance imaging (MRI) or other imaging tests, scalp electroencephalography (EEG) could be suggestive of bilateral ictal onset or even ictal onset contralateral to the dominant imaging abnormality. We aimed to investigate the role of scalp EEG lateralization pre-operatively in predicting outcome.
  
  
  METHODS
  We retrospectively reviewed 54 patients who underwent hemispherectomy between 1991 and 2009 at Medical College of Georgia (1991-2006) and Cincinnati Children's Hospital Medical Center (2006-2009) and had at least one year post-operative follow-up. All preoperative EEGs were reviewed, and classified as either lateralizing or nonlateralizing, for both ictal and interictal EEG recordings.
  
  
  RESULTS
  Of 54 patients, 42 (78%) became seizure free. Twenty-four (44%) of 54 had a nonlateralizing ictal or interictal EEG. Further analysis was based on etiology of epilepsy, including malformation of cortical development (MCD), Rasmussen syndrome (RS), and stroke (CVA). EEG nonlateralization did not predict poor outcome in any of the etiology groups evaluated.
  
  
  CONCLUSIONS
  Scalp EEG abnormalities in contralateral or bilateral hemispheres do not, in isolation, predict a poor outcome from hemispherectomy. Results of other non-invasive and invasive evaluations should be used to determine candidacy.
authors.affiliation: Department of Pediatrics, Division of Child Neurology, Cincinnati Children's, Hospital Medical Center, 3333 Burnet Avenue, MLC 2015, Cincinnati, OH, United States.
authors.forename: Hansel M
authors.initials: HM
authors.lastname: Greiner
authors.forename: Yong D
authors.initials: YD
authors.lastname: Park
authors.forename: Katherine
authors.initials: K
authors.lastname: Holland
authors.forename: Paul S
authors.initials: PS
authors.lastname: Horn
authors.forename: Anna W
authors.initials: AW
authors.lastname: Byars
authors.forename: Francesco T
authors.initials: FT
authors.lastname: Mangano
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Smith
authors.forename: Mark R
authors.initials: MR
authors.lastname: Lee
authors.forename: Ki-Hyeong
authors.initials: KH
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality / Q000502:physiology*; D038421:Hemispherectomy; D006801:Humans; D007223:Infant; D008297:Male; D012189:Retrospective Studies; D012535:Scalp / Q000503:physiopathology; D016896:Treatment Outcome; D055815:Young Adult