Focal epilepsy is a neurological condition that involves the cyclical recurrence of seizures. However, the prevalence and patterns of seizure cycles are not known. This study aims to establish the prevalence, strength, and temporal patterns of seizure cycles across multiple timescales.

 This retrospective cohort study included a total of 222 participants with medically refractory focal epilepsy. The selection criteria were the availability of cEFG and/or self-reports of disabling seizures. All participants took antiseizure medications and responsive neurostimulation based on clinical indications. The primary outcomes of this study were self-reported daily seizure counts, cEFG-based hourly counts, and detections of interictal epileptiform activity (IEA).

 The findings suggested that the prevalence was 12% of circannual seizure cycles, 60% for multidien seizure cycles, and 89% of circadian seizure cycles. The strengths of circadian and multidien seizure cycles were similar, whereas circannual seizure cycles were weaker. The individual-based analysis showed that circadian seizure cycles showed five peaks in a day, and multidien cycles showed peaks at 7, 15, 20, and 30 days. Electrographic and self-reported seizures consistently occurred during the phase of multidien IEA cycles.

 The research concluded that the prevalence of plural seizure cycles was high, which helped explain the natural variability of the timing of seizures.