title: Unfavorable surgical outcomes in partial epilepsy with secondary bilateral synchrony: Intracranial electroencephalography study.
abstract: OBJECTIVE
  Secondary bilateral synchrony (SBS) indicates bilaterally synchronous epileptiform discharges arising from a focal cortical origin. The present study aims to investigate SBS in partial epilepsy with regard to surgical outcomes and intracranial EEG findings.
  
  
  METHODS
  We retrospectively reviewed consecutive patients who underwent epilepsy surgery following extraoperative intracranial electroencephalography (EEG) study from 2008 to 2012. The presence of SBS was determined based upon the results of scalp EEG monitoring performed for presurgical evaluations. We reviewed scalp EEG, neuroimaging, intracranial EEG findings, and surgical outcomes in patients with SBS.
  
  
  RESULTS
  We found 12 patients with SBS who were surgically treated for intractable partial epilepsy. Nine (75%) patients had lateralized ictal semiology and only two (16.6%) patients showed localized ictal onset in scalp EEG. Brain MRI showed epileptogenic lesion in three (25%) patients. Intracranial EEG demonstrated that ictal onset zone was widespread or non-localized in six (50%) patients. Low-voltage fast activity was the most common ictal onset EEG pattern. Rapid propagation of ictal onset was noted in 10 (83.3%) patients. Eleven patients underwent resective epilepsy surgery and only two patients (18.2%) achieved seizure-freedom (median follow-up 56 months). MRI-visible brain lesions were associated with favorable outcomes (p=0.024). Patients with SBS, compared to frontal lobe epilepsy without SBS, showed lesser localization in ictal onset EEG (p=0.029) and more rapid propagation during evolution of ictal rhythm (p=0.015).
  
  
  CONCLUSIONS
  The present results suggested that resective surgery for partial epilepsy with SBS should be decided carefully, especially in case of nonlesional epilepsy. Poor localization and rapid spread of ictal onset were prominent in intracranial EEG, which might contribute to incomplete resection of the epileptogenic zone and poor surgical outcomes.
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea; Department of Neurology, Soonchunhyang University School of Medicine, Seoul, South Korea.
authors.forename: Jun-Sang
authors.initials: JS
authors.lastname: Sunwoo
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea; Department of Neurology, Kyung Hee University Hospital at Gangdong, Seoul, South Korea.
authors.forename: Jung-Ick
authors.initials: JI
authors.lastname: Byun
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Jangsup
authors.initials: J
authors.lastname: Moon
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Jung-Ah
authors.initials: JA
authors.lastname: Lim
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Tae-Joon
authors.initials: TJ
authors.lastname: Kim
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Soon-Tae
authors.initials: ST
authors.lastname: Lee
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Keun-Hwa
authors.initials: KH
authors.lastname: Jung
authors.affiliation: Department of Neurology, Seoul National University Hospital Healthcare System Gangnam Center, Seoul, South Korea.
authors.forename: Kyung-Il
authors.initials: KI
authors.lastname: Park
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Kon
authors.initials: K
authors.lastname: Chu
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea; Protein Metabolism Medical Research Center, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Manho
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Chun-Kee
authors.initials: CK
authors.lastname: Chung
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea. Electronic address: jungky10@gmail.com.
authors.forename: Ki-Young
authors.initials: KY
authors.lastname: Jung
authors.affiliation: Department of Neurology, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, South Korea; Program in Neuroscience, Seoul National University College of Medicine, Seoul, South Korea. Electronic address: sangkun2923@gmail.com.
authors.forename: Sang Kun
authors.initials: SK
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D003344:Cortical Synchronization; D000069279:Drug Resistant Epilepsy / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery*; D000069280:Electrocorticography; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery*; D017034:Epilepsy, Frontal Lobe / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011379:Prognosis; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult
keywords: Epilepsy surgery; Intracranial electroencephalography; Secondary bilateral synchrony; Surgical outcome