title: Tailoring epilepsy surgery with fast ripples in the intraoperative electrocorticogram.
abstract: OBJECTIVE
  Intraoperative electrocorticography (ECoG) can be used to delineate the resection area in epilepsy surgery. High-frequency oscillations (HFOs; 80-500 Hz) seem better biomarkers for epileptogenic tissue than spikes. We studied how HFOs and spikes in combined pre- and postresection ECoG predict surgical outcome in different tailoring approaches.
  
  
  METHODS
  We, retrospectively, marked HFOs, divided into fast ripples (FRs; 250-500 Hz) and ripples (80-250 Hz), and spikes in pre- and postresection ECoG sampled at 2,048 Hz in people with refractory focal epilepsy. We defined four groups of electroencephalography (EEG) event occurrence: pre+post- (+/-), pre+post+ (+/+), pre-post+ (-/+) and pre-post- (-/-). We subcategorized three tailoring approaches: hippocampectomy with tailoring for neocortical involvement; lesionectomy of temporal lesions with tailoring for mesiotemporal involvement; and lesionectomy with tailoring for surrounding neocortical involvement. We compared the percentage of resected pre-EEG events, time to recurrence, and the different tailoring approaches to outcome (seizure-free vs recurrence).
  
  
  RESULTS
  We included 54 patients (median age, 15.5 years; 25 months of follow-up; 30 seizure free). The percentage of resected FRs, ripples, or spikes in pre-ECoG did not predict outcome. The occurrence of FRs in post-ECoG, given FRs in pre-ECoG (+/-, +/+), predicted outcome (hazard ratio, 3.13; confidence interval = 1.22-6.25; p = 0.01). Seven of 8 patients without spikes in pre-ECoG were seizure free. The highest predictive value for seizure recurrence was presence of FRs in post-ECoG for all tailoring approaches.
  
  
  CONCLUSIONS
  FRs that persist before and after resection predict poor postsurgical outcome. These findings hold for different tailoring approaches. FRs can thus be used for tailoring epilepsy surgery with repeated intraoperative ECoG measurements. Ann Neurol 2017;81:664-676.
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Maryse A
authors.initials: MA
authors.lastname: van 't Klooster
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Nicole E C
authors.initials: NEC
authors.lastname: van Klink
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Willemiek J E M
authors.initials: WJEM
authors.lastname: Zweiphenning
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Frans S S
authors.initials: FSS
authors.lastname: Leijten
authors.affiliation: Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
authors.forename: Rina
authors.initials: R
authors.lastname: Zelmann
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Cyrille H
authors.initials: CH
authors.lastname: Ferrier
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Peter C
authors.initials: PC
authors.lastname: van Rijen
authors.affiliation: Brain Center Rudolf Magnus, Department of Child Neurology, UMC Utrecht, Utrecht, The Netherlands.|Biomedical MR Imaging and Spectroscopy Group, Center for Image Sciences, UMC Utrecht, Utrecht, The Netherlands.|Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands.
authors.forename: Willem M
authors.initials: WM
authors.lastname: Otte
authors.affiliation: Brain Center Rudolf Magnus, Department of Child Neurology, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Kees P J
authors.initials: KPJ
authors.lastname: Braun
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Geertjan J M
authors.initials: GJM
authors.lastname: Huiskamp
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.|Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands.
authors.forename: Maeike
authors.initials: M
authors.lastname: Zijlmans
mesh_terms: D000293:Adolescent; D000328:Adult; D058256:Brain Waves / Q000502:physiology*; D002648:Child; D000069279:Drug Resistant Epilepsy / Q000601:surgery; D000069280:Electrocorticography / Q000379:methods*; D004828:Epilepsies, Partial / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods*; D008297:Male; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011379:Prognosis; D055815:Young Adult