title: Characteristics of dipoles in clustered individual spikes and averaged spikes.
abstract: The aim of this study is to analyze the characteristics of dipoles in clustered individual spikes and averaged spikes, we compared electroencephalography (EEG) dipole localizations from patients with intractable extratemporal lobe epilepsy (IETLE) and from patients with benign epilepsy with centrotemporal spikes (BECTS). We studied 10 patients; five with IETLE who underwent epilepsy surgery after subdural EEG and five with BECTS. We recorded 19-channel digital scalp EEGs and used clustering analysis for individual spikes to characterize interictal spikes. We selected and averaged one representative spike group at the maximum negative peak electrode. We used a single dipole method with three-shell spherical head model. We compared dipole localizations of both averaged and individual spikes.IETLE data had more identifiable spike clusters and fewer spikes in each cluster than BECTS (P<0.05). Dipole sources with goodness-of-fit >or=95% in averaged spikes were less frequent in IETLE than in BECTS (P<0.05). For IETLE, averaged spikes showed no dipoles (two patients), while individual spikes gave dipole sources reliably in the epileptic region. For BECTS, individual and averaged spike sources were clustered. More than 80% of dipoles in averaged spikes were stable, in close proximity, for prolonged periods in BECTS. More spike groups after clustering and fewer acceptable dipoles from averaged spikes in IETLE reflect variable spike activity over extensive epileptic regions. Fewer spike groups producing more acceptable dipoles in BECTS correlate with stable spike sources within the isolated epileptic central region. Characteristics of clustered interictal spikes need careful examination before the use of dipole analysis of averaged spikes for epilepsy evaluation.
authors.affiliation: Department of Paediatrics, Division of Neurology, The Hospital for Sick Children, University of Toronto, 555 University Avenue, ON, Toronto, Canada M5G 1X8.
authors.forename: Shiro
authors.initials: S
authors.lastname: Chitoku
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Otsubo
authors.forename: Takashi
authors.initials: T
authors.lastname: Ichimura
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Saigusa
authors.forename: Ayako
authors.initials: A
authors.lastname: Ochi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Shirasawa
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Kamijo
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Pang
authors.forename: James T
authors.initials: JT
authors.lastname: Rutka
authors.forename: Shelly K
authors.initials: SK
authors.lastname: Weiss
authors.forename: O Carter
authors.initials: OC
authors.lastname: Snead
mesh_terms: D000293:Adolescent; D001921:Brain / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male