title: Intracranially recorded ictal direct current shifts may precede high frequency oscillations in human epilepsy.
abstract: OBJECTIVE
  We assessed the temporal-spatial characteristics of ictal direct current (DC) shifts (or infraslow activity) and high frequency oscillations (HFOs) in 16 patients with intractable focal epilepsy.
  
  
  METHODS
  The underlying etiology consisted of cortical dysplasia, glioma, hippocampal sclerosis, and low-grade neuroepithelial tumor in nine, four, two, and one patients, respectively. The median number of analyzed seizure events was 8.0 per patient (range: 2-10). Chronic electrocorticographic recording was performed with (1) a band-pass filter of 0.016-600Hz (or 0.016-300Hz) and a sampling rate of 2000Hz (or 1000Hz).
  
  
  RESULTS
  Ictal DC shifts and a sustained form of ictal HFOs were observed in 75.0% and 50.0% of the patients, and 71.3% and 46.3% of the analyzed seizures. Visual assessment revealed that the onset of ictal DC shifts preceded that of ictal HFOs with statistical significance in 5/7 patients. The spatial extent of ictal DC shifts or HFOs was smaller than that of the conventionally defined seizure onset zone in 9/12 patients.
  
  
  CONCLUSIONS
  Both ictal DC shifts and HFOs might represent the core of tissue generating seizures.
  
  
  CONCLUSIONS
  The early occurrence of ictal DC shifts warrants further studies to determine the role of glia (possibly mediating ictal DC shifts) in seizure generation.
authors.affiliation: Department of Neurology, Kyoto University, Kyoto, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kanazawa
authors.affiliation: Department of Epilepsy, Movement Disorders and Physiology, Kyoto University, Kyoto, Japan.
authors.forename: Riki
authors.initials: R
authors.lastname: Matsumoto
authors.affiliation: Department of Neurology, Kyoto University, Kyoto, Japan.
authors.forename: Hisaji
authors.initials: H
authors.lastname: Imamura
authors.affiliation: Human Brain Research Center, Kyoto University, Kyoto, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Matsuhashi
authors.affiliation: Department of Neurosurgery, Kyoto University, Kyoto, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kikuchi
authors.affiliation: Department of Neurosurgery, Kyoto University, Kyoto, Japan.
authors.forename: Takeharu
authors.initials: T
authors.lastname: Kunieda
authors.affiliation: Department of Neurological Surgery, Sapporo Medical University, Sapporo, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Mikuni
authors.affiliation: Department of Neurosurgery, Kyoto University, Kyoto, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Miyamoto
authors.affiliation: Department of Neurology, Kyoto University, Kyoto, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Takahashi
authors.affiliation: Department of Epilepsy, Movement Disorders and Physiology, Kyoto University, Kyoto, Japan. Electronic address: akio@kuhp.kyoto-u.ac.jp.
authors.forename: Akio
authors.initials: A
authors.lastname: Ikeda
mesh_terms: D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation / Q000379:methods*; D004827:Epilepsy / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D055815:Young Adult
keywords: DC shift; Epilepsy; Focal cortical dysplasia; Glioma; High-frequency oscillation; Infraslow activity