EEG frequency profiles of idiopathic generalised epilepsy syndromes

Abstract

The objective of this study was to investigate EEG frequency profiles (topographic distribution of spectral power data) in well-defined idiopathic generalised epilepsy (IGE) syndromes: juvenile absence epilepsy (JAE), juvenile myoclonic epilepsy (JME), epilepsy with grand mal seizures on awakening (EGMA), and in the unified ‘common IGE’ (CIGE) group of these patients. Methods: Absolute and relative (percent) power values were computed from waking EEG activity by Fast Fourier Transform (FFT). Each patient group was compared to an age-matched group of healthy control persons. Results: There was a general tendency for diffuse (absolute and relative) delta–theta–alpha power excess and relative beta power deficit in all IGE groups as compared to controls. Statistically significant ( P≤0.05) bilateral absolute power differences were: fronto-parietal delta and diffuse theta (in JAE), frontal delta (in JME) and frontal alpha (in EGMA). Statistically significant ( P≤0.05) relative power differences were: frontal delta, diffuse theta, fronto-centro-parietal beta (in JAE), frontal delta and beta (in JME) and fronto-central alpha (in EGMA). The CIGE group showed power alterations of the same type but differences were statistically more significant than in the other patient groups. Conclusion: Absolute power findings were interpreted as enhanced neuronal synchrony in the 0.5–12.0 Hz frequency range together with the tendency of decreasing synchrony in faster (12.5–32.0 Hz) frequencies. Corresponding shifts in relative power were interpreted as reflecting dysfunction of cortical regions. The authors hypothesise that these IGE frequency profiles reflect widespread cortical dysfunction essentially common to all the investigated IGE syndromes.