title: Resection of individually identified high-rate high-frequency oscillations region is associated with favorable outcome in neocortical epilepsy.
abstract: OBJECTIVE
  High-frequency oscillations (HFOs) represent a novel electrophysiologic marker of endogenous epileptogenicity. Clinically, this propensity can be utilized to more accurately delineate the resection margin before epilepsy surgery. Currently, prospective application of HFOs is limited because of a lack of an exact quantitative measure to reliably identify HFO-generating areas necessary to include in the resection. Here, we evaluated the potential of a patient-individualized approach of identifying high-rate HFO regions to plan the neocortical resection.
  
  
  METHODS
  Fifteen patients with neocortical seizure-onset zones (SOZs) underwent intracranial electroencephalographic monitoring. To identify interictal HFOs, we applied an automated, hypersensitive HFO-detection algorithm followed by post hoc processing steps to reject false detections. The spatial relationship between HFO distribution and the SOZ was evaluated. To address high interpatient variability in HFO properties, we evaluated the high-rate HFO region, an unbiased statistical parameter, in each patient. The relationship between resection of the high-rate HFO region and postoperative outcome was examined.
  
  
  RESULTS
  Grouped data demonstrated that the rate of ripple (60-200 Hz) and fast ripple (200-500 Hz) was increased in the SOZ (both p < 0.01). Intrapatient analysis of the HFO distribution localized the SOZ in 11 patients. High-rate HFO regions were determined in all patients by an individually adjusted threshold. Resection of high-rate HFO regions was significantly associated with a seizure-free outcome (p < 0.01). The extent/ratio of SOZ or spiking region resection did not differ between seizure-free and seizure-persistent groups.
  
  
  CONCLUSIONS
  Intrapatient analysis of high-rate HFOs provides more detailed description of HFO-generating areas and can mark the areas of clinically significant epileptogenicity--a crucial component of the neocortical epileptic network that should be removed to achieve a good outcome. Validating and adopting an unbiased quantitative HFO parameter has the potential to propel wider and prospective utilization of HFOs in the surgical treatment of neocortical epilepsy and to improve its outcome.
authors.affiliation: Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Samsung Biomedical Research Institute, Seoul, Korea; Division of Computation and Neural Systems, California Institute of Technology, Pasadena, California, U.S.A.
authors.forename: Jounhong Ryan
authors.initials: JR
authors.lastname: Cho
authors.forename: Dae Lim
authors.initials: DL
authors.lastname: Koo
authors.forename: Eun Yeon
authors.initials: EY
authors.lastname: Joo
authors.forename: Dae Won
authors.initials: DW
authors.lastname: Seo
authors.forename: Seung-Chyul
authors.initials: SC
authors.lastname: Hong
authors.forename: Premysl
authors.initials: P
authors.lastname: Jiruska
authors.forename: Seung Bong
authors.initials: SB
authors.lastname: Hong
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods; D019579:Neocortex / Q000503:physiopathology*; D011446:Prospective Studies; D055815:Young Adult
keywords: Automated detection; Epilepsy surgery; High-frequency oscillations; Neocortical epilepsy; Surgical outcome