Temporal distribution of clinical seizures over the 24-h day: a retrospective observational study in a tertiary epilepsy clinic.

PURPOSE

Very few studies have evaluated seizure occurrence in humans over the 24-h day; data from children are particularly scarce. Circadian patterns in seizure occurrence may be of importance in epilepsy research and may have important implications in diagnosis and therapy.

METHODS

We have analyzed clinical seizures of 176 consecutive patients (76 children, 100 adults) who had continuous electroencephalography (EEG) and video monitoring lasting more than 22 h. Several aspects of seizures were noted, including classification, time of day, origin, and sleep stage.

RESULTS

More than 800 seizures were recorded. Significantly more seizures were observed from 11:00 to 17:00 h, and from 23:00 to 05:00 h significantly fewer seizures were seen. The daytime peak incidences were observed in seizures overall, complex partial seizures (in children and adults), seizures of extratemporal origin (in children), and seizures of temporal origin (in adults). Incidences significantly lower than expected were seen in the period 23:00 to 05:00 h in seizures overall, complex partial seizures (in children and adults), and in tonic seizures (in children). In addition, significantly fewer seizures of temporal (in children and adults) and extratemporal origin (in children) were observed in this period.

DISCUSSION

The results suggest that certain types of seizures have a strong tendency to occur in true diurnal patterns. These patterns are characterized by a peak during midday and a low in the early night.