Syndrome defined as a cryptogenic or symptomatic generalised epilepsy, which is characterised by the following symptomatic triad: several epileptic seizures (atypical absences, axial tonic seizures and sudden atonic or myoclonic falls); diffuse slow interictal spike waves in the waking EEG (< 3 Hz) and fast rhythmic bursts (10 Hz) during sleep; slow mental development associated with personality disturbances.