title: Correlation between scalp-recorded electroencephalographic and electrocorticographic activities during ictal period.
abstract: OBJECTIVE
  To investigate the correlation between scalp-recorded electroencephalographic (EEG) and electrocorticographic (ECoG) activities during ictal periods.
  
  
  METHODS
  Simultaneous EEG and ECoG recordings with chronic subdural electrodes were performed in eight patients with partial epilepsy.
  
  
  RESULTS
  In two cases where the ictal ECoG discharges originated in deep brain structures such as the hippocampus and interhemispheric surface of the frontal lobe, ictal discharges could not be detected on EEG until they expanded to the cortex of convexity. In four cases, the ictal onset zones were located in the lateral convexity. When synchronous or near synchronous ictal ECoG discharges with amplitudes of 200-2000muV were recorded on more than 8-15cm(2) of cortex, corresponding discharges were recorded on EEG in these four cases. However, in a case of frontal lobe epilepsy, asynchronous ictal ECoG discharges were recorded on 10 electrodes of convexity but no ictal EEG activity was recorded. Furthermore, in two frontal lobe epilepsy cases, ictal EEG discharges did not always reflect the ictal ECoG spike, but occasionally reflected slow background ECoG activity around the ictal discharges.
  
  
  CONCLUSIONS
  Multiple factors such as the width of the cortical area involved, amplitude of ictal discharges and degree of synchronization of electrical potentials play important roles in the appearance of ictal EEG recordings, and the relationship between ictal EEG and ECoG is not straightforward.
authors.affiliation: Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Kimiaki
authors.initials: K
authors.lastname: Hashiguchi
authors.forename: Takato
authors.initials: T
authors.lastname: Morioka
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Yoshida
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Miyagi
authors.forename: Shinji
authors.initials: S
authors.lastname: Nagata
authors.forename: Ayumi
authors.initials: A
authors.lastname: Sakata
authors.forename: Tomio
authors.initials: T
authors.lastname: Sasaki
mesh_terms: D000293:Adolescent; D000328:Adult; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017966:Pyramidal Cells / Q000503:physiopathology*; D012640:Seizures / Q000503:physiopathology*; D014741:Video Recording