Abstracts

Identification of a focal nature from generalized spike-and-wave discharges (GSWD) may have important implications for the treatment of intractable epilepsy. Independent component analysis (ICA) can separate complex multichannel data into spatially fixed and temporally independent components. To differentiate between primary and secondary bilateral synchrony (PBS and SBS, respectively), we applied ICA to GSWD, and analyzed the characteristic patterns of independent components. Electroencephalograms (EEGs) from 19 patients with GSWD (9 PBS patients, 10 SBS patients) were studied. Thirty GSWD epochs (from [ndash]0.2 to +0.3 s from the negative maximum of the spike) were selected and concatenated to construct an EEG data matrix that was subjected to ICA. Because spikes that have different spatial distributions produce different ICA components, selected independent components were localized by mapping them on a spherical model of the head by means of brain electrical source analysis (BESA) to define dipole sources. Epileptic components of GSWD were clearly separated by the ICA algorithm. Between one and three components per patient were responsible for GSWD. While the epileptic components of GSWD in PBS patients were bilaterally symmetrical radial dipoles that were located primarily within the dorsolateral frontal region, epileptic components in SBS patients were asymmetrical mixed dipoles that were located primarily within the medial frontal region. Spatiotemporal decomposition of independent components of GSWD by using ICA can be useful for differentiating SBS from PBS. The localization of the dipole sources of the independent components provides further insight into the pathophysiological origins of GSWD.