Continuous spike-and-wave activity during slow-wave sleep: syndrome or EEG pattern?

We reviewed the electroclinical pictures and clinical characteristics of 32 patients with continuous spike-and-wave activity during slow sleep (CSWS) to ascertain to what extent this electroencephalogram (EEG) pattern is associated with the age-related CSWS syndrome as defined by the International League Against Epilepsy (ILAE) International Classification or with different clinical settings.

We reviewed clinical and EEG characteristics of 32 CSWS patients.

In all patients, detection of CSWS coincided with a worsening of neurologic status. Ten (34%) patients had the typical features of CSWS syndrome, four were classified as having Landau-Kleffner syndrome, and three had acquired opercular syndromes. The remaining 15 patients, all with symptomatic epilepsy, had CSWS, which lasted for variable periods and might be related to inappropriate drug choice. Three patients of this group had unilateral CSWS and exhibited worsening of spontaneous movements in the hemibody contralateral to CSWS activity lasting for a few hours after awakening.

Our data show that a number of factors can intervene in the genesis of CSWS, which may explain the variability of the associated clinical conditions. In view of this etiologic heterogeneity, it is not possible to classify all the patients with CSWS as having the CSWS syndrome. Therefore, the CSWS syndrome should be considered a category embracing a limited group of patients, whereas the EEG pattern of CSWS is seen commonly in various clinical conditions.