Abstracts

Rationale: Generalized spike-wave (GSW) discharges are the main electroencephalographic characteristics of idiopathic generalized epilepsies (IGE). Event-related spectral perturbation (ERSP) analysis quantifies changes triggered by events in the spectral power plot of the electroencephalogram (EEG). The aim of this study was to evaluate the presence of focal activity in generalized discharges of patients with IGE using the ERSP analysis. Methods: 32 patients (14 women, mean age 32±14 years) with IGE were investigated. The patients were submitted to routine EEG which was performed in a 22 channels recorder, with 20 minutes duration, 10-20 electrode placement system, photostimulation and hyperventilation. EEGLAB software was used for EEG processing and analysis. GSW discharges were visually selected and excerpts of 4 seconds centered in the onset of generalized discharge were stored. Then, a spectral plot was generated for each electrode. Finally, a mean of all electrodes was calculated and analyzed. Results: 253 discharges (mean 8±12 per patient) were evaluated. The spectral responses obtained in the evaluation of the mean of all channels in the moment of discharges showed changes in electrodes: Fp1, Fp2, F3 e F4 (4.7, 5, 4.6 and 5dB respectively). After 127 ms, similar changes were noticed corresponding to the slow component of the discharge in these same electrodes (5.2, 4.8, 5.1 e 4.9dB). Conclusions: This investigation supports that frontal regions constitute the initial source of generalized discharges. Subsequently, there is fast spread and involvement of greater projection networks.