Abstracts

Rationale: Continuous spike and waves during sleep (CSWS) is characterized by excessive accelerations of epileptiform discharges on EEG during sleep. Children with CSWS present with mental retardation, global regression and seizures. They are classified as epileptic encephalopathy with CSWS (ECSWS), atypical benign partial epilepsy (ABPE) and Landau-Kleffner syndrome (LKS). We analyzed characteristics of MEG findings in children with CSWS.Methods: We analyzed MEG in 7 patients with CSWS. They were 4 boys and 3 girls. Age at MEG ranged between 4 and 11 years with a mean of 7.9 years. All patients did not have any brain lesions on MRI. MEG was performed with whole-head 151-channel gradiometers. Sampling rate was 625/1250 Hz. We recorded 15 to 20 data sets of 2-minute periods during sleep. We selected the initial spikes in runs of diffuse/generalized spike and waves during sleep to analyze early phase of the spikes and localize MEG spike source (MEGSS) with band pass filter of 10-50/70Hz.Results: Seven patients consisted of 3 ECSWS, 2 ABPE and 2 LKS. MEG showed clustered MEGSSs in all 7 patients. Bilateral clusters were found in 3 patients. Number of MEGSSs ranged from27 to 143 with a mean of 92. The orientations of clustered MEGSSs were identical. MEGSSs were confined densely within 3 cubic cm in 3 ECSWS and 2 LKS patients with rare seizures. Clusters of MEGSSs in 3 ECSWS patients located in multifocal areas. Clusters of MEGSSs in 2 ABPE patients located in the unilateral peri-Rolandic region. Clusters of MEGSSs in 2 LKS patients located in the predominant posterior portion of the left superior temporal gyrus and perisylvian regions, including Heschl s gyrus.Conclusions: The locations of clustered MEGSSs in ABPE and LKS differed from those in ECSWS. The specific locations, the small and tight clusters and the identical orientation of MEGSSs correlated with unique features of functional disorders and seizures in patients with CSWS.