Time distribution of seizures during long-term video-EEG monitoring

The purpose of this study was to investigate the duration of monitoring, number of seizures recorded, and date and time of occurrence of seizures in different patient groups during video-EEG monitoring (VEEGM). Patients with partial or psychogenic seizures who were admitted to our VEEGM unit between September 1996 and March 2002 were retrospectively evaluated. Duration of monitoring, date and time of occurrence of seizures were identified in each patient. For practical reasons, a day was divided into 3 equal time periods (period 1: 08-16; period II: 16-24 and period III: 24-08 hrs), and the period in which the seizure occurred was noted. Patients were classified in 5 groups: 1-temporal; 2-frontal; 3-parieto-occipital; 4-psychogenic and 5-unclassified. Duration of monitoring, the number of seizures recorded and time distribution of seizures were identified in each group and compared statistically. We evaluated 746 seizures in 209 patients. Seizures were more likely to occur in periods I and III in groups 1 (p = 0.004) and 5 (p < 0.001). In group 4 they were more likely to occur in periods I and II (p < 0.001). Duration of monitoring was not statistically different between the groups. However, the number of seizures recorded varied significantly (p = 0.006). Patients in group 5 had the greatest number of seizures and were followed by groups 2, 4, 3 and 1, respectively. Groups also differed according to date of seizure occurrence (p < 0.001). We conclude that the number of seizures recorded and time distribution of seizures during VEEGM are influenced by the lobe of onset of seizures.