title: Focal resection of fast ripples on extraoperative intracranial EEG improves seizure outcome in pediatric epilepsy.
abstract: OBJECTIVE
  High-frequency oscillations (HFOs), termed ripples at 80-200 Hz and fast ripples (FRs) at >200/250 Hz, recorded by intracranial electroencephalography (EEG), may be a valuable surrogate marker for the localization of the epileptogenic zone. We evaluated the relationship of the resection of focal brain regions containing high-rate interictal HFOs and the seizure-onset zone (SOZ) determined by visual EEG analysis with the postsurgical seizure outcome, using extraoperative intracranial EEG monitoring in pediatric patients and automated HFO detection.
  
  
  METHODS
  We retrospectively analyzed 28 pediatric epilepsy patients who underwent extraoperative intracranial video-EEG monitoring prior to focal resection. Utilizing the automated analysis, we identified interictal HFOs during 20 min of sleep EEG and determined the brain regions containing high-rate HFOs. We investigated spatial relationships between regions with high-rate HFOs and SOZs. We compared the size of these regions, the surgical resection, and the amount of the regions with high-rate HFOs/SOZs within the resection area with seizure outcome.
  
  
  RESULTS
  Ten patients were completely seizure-free and 18 were not at 2 years after surgery. The brain regions with high-rate ripples were larger than those with high-rate FRs (p = 0.0011) with partial overlap. More complete resection of the regions with high-rate FRs significantly correlated with a better seizure outcome (p = 0.046). More complete resection of the regions with high-rate ripples tended to improve seizure outcome (p = 0.091); however, the resection of SOZ did not influence seizure outcome (p = 0.18). The size of surgical resection was not associated with seizure outcome (p = 0.22-0.39).
  
  
  CONCLUSIONS
  The interictal high-rate FRs are a possible surrogate marker of the epileptogenic zone. Interictal ripples are not as specific a marker of the epileptogenic zone as interictal FRs. Resection of the brain regions with high-rate interictal FRs in addition to the SOZ may achieve a better seizure outcome.
authors.affiliation: Division of Neurology, The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Akiyama
authors.forename: Bláthnaid
authors.initials: B
authors.lastname: McCoy
authors.forename: Cristina Y
authors.initials: CY
authors.lastname: Go
authors.forename: Ayako
authors.initials: A
authors.lastname: Ochi
authors.forename: Irene M
authors.initials: IM
authors.lastname: Elliott
authors.forename: Mari
authors.initials: M
authors.lastname: Akiyama
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Donner
authors.forename: Shelly K
authors.initials: SK
authors.lastname: Weiss
authors.forename: O Carter
authors.initials: OC
authors.lastname: Snead
authors.forename: James T
authors.initials: JT
authors.lastname: Rutka
authors.forename: James M
authors.initials: JM
authors.lastname: Drake
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Otsubo
mesh_terms: D000293:Adolescent; D001921:Brain / Q000503:physiopathology / Q000601:surgery; D002648:Child; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D007223:Infant; D008991:Monitoring, Physiologic; D012189:Retrospective Studies; D012640:Seizures / Q000503:physiopathology* / Q000601:surgery; D016896:Treatment Outcome; D014741:Video Recording