Relationship of sigma activity to sleep interictal epileptic discharges: astudy in children affected by benign epilepsy with occipital paroxysms

Introduction: By applying spectral analysis techniques we recently showed t hat Interictal Epileptic Discharges (IEDs) are modulated by sleep spindle s ynchronization mechanisms (sigma activity, SA, 12.0-16.0 Hz). This finding applies to both benign epilepsy of childhood with rolandic spikes (BECRS), to symptomatic epilepsy of childhood strongly activated by sleep and to the Landau-Kleffner syndrome. These results are quite different from those fou nd in adult partial epileptic patients where slow wave activity (SWA, 0.5-4 .5 Hz) plays the main role in the modulation of IEDs during sleep. This fin ding could suggest that the activation of IEDs by spindle activities could be an age-related feature of epilepsy. In order to verify this hypothesis w e studied a group of epileptic children performing a polysomnographic study on five patients with BEOP strongly activated by sleep. Methods: We perfor med overnight continuous EEG-polysomnographic studies in five patients (mea n age 6.0 +/- 2.5). The IEDs count was performed on the most active occipit al lead. The temporal series of SWA and SA values. derived from spectral an alysis, were obtained fr om a spike-free central, controlateral lead. Relat ionships between SAI SWA and time series of IEDs were tested by means of co rrelation techniques after data normalization. Results: Our results reveale d a significantly higher correlation between IEDs and SA with respect to SW A in all subjects, in total sleep time. When the analysis was limited only to NREM sleep the correlation between sigma and IEDs was even more impressi ve. Conclusions: Data suggest that also in BEOP the spindle generating mech anism modulates the IEDs during sleep. This mechanism seems to be an age-de pendent phenomenon with no I elation whatsoever either with the type of epi lepsy or with the brain region. (C) 2000 Published by Elsevier Science B.V. All rights reserved.