Relationship of sleep interictal epileptiform discharges to sigma activity(12-16 Hz) in benign epilepsy of childhood with rolandic spikes

Objective: The activation of interictal epileptic discharges (IEDs) by NREM sleep is a well-known phenomenon in benign epilepsy of childhood with rola ndic spikes (BECRS). The activating properties of NREM sleep on IEDs have b een attributed to increased synchronization within thalamocortical neurons. During NREM sleep two synchronizing mechanisms lead to the appearance of s pindles and delta waves on the EEG. Spectral analysis technique is a suitab le method that can be used to quantitatively describe the dynamics of delta (slow wave activity (SWA) 0.5-4.0 Hz) and sigma activity (12.0-16.0 Hz) du ring sleep. Methods: In order to define more accurately the relationship between synchr onizing mechanisms (spindles and delta activities) and IEDs during sleep in BECRS, we have performed overnight continuous EEG polysomnography studies in 9 patients (mean age 7.4 +/- 2.5 years). The temporal series of SWA and sigma values, derived from spectral analysis, have been obtained from a spi ke-free derivation lead. The IEDs count has been performed on the most acti ve lead. Relationships between sigma and SWA and time series of IEDs were t ested by means of correlation techniques after data normalization. Results: Our results revealed a significant higher correlation between IEDs and sigma activity with respect to SWA in all the subjects, in total sleep time. The same analysis limited to NREM sleep highlights the better correl ation between sigma and IEDs. Conclusions: Data suggest that during sleep of BECRS patients, IEDs are mor e sensitive to the promoting action of the spindle-generating mechanism tha n to the SWA-producing one. (C) 1999 Elsevier Science Ireland Ltd. All righ ts reserved.