Cycles of seizure events in a person with epilepsy

Evidence suggests that the momentary likelihood of a seizure is co-modulated by cycles running on divergent timescales.¹ Circadian seizure cycles are the most prevalent (~90%), with peak seizure incidence occurring at specific times of day with substantial variability, but also shared patterns, across individuals (i.e., seizure chronotypes).¹ This variability is likely driven by endogenous circadian factors as well as the timing of behaviours such as sleep, eating or taking medication.¹ Seizures are more common around sleep-wake transitions, so late evening and/or early morning seizure chronotypes have been observed at the population level.¹ People with sleep-related epilepsy can have a peak seizure time soon after falling asleep (typically before midnight) or in late stages of sleep (typically at dawn); these are unlikely to be fully explained by the differential effects of rapid eye movement (REM) and non-REM phases of sleep on seizures.¹

EEG data show that individual seizure chronotypes are fairly stable over months or years.¹ However, preferential seizure times may spontaneously change, with dramatic practical implications for patients’ day-to-day life.¹ Seizure chronotypes may differ between paediatric and adult populations, possibly due to age-dependent differences in sleep–wake cycles or hormonal or behavioural factors, or due to the development of intrinsic circadian regulatory mechanisms in the brain.¹

Reference:

1. Karoly PJ, Rao VR, Gregg NM, et al. Cycles in epilepsy. Nat Rev Neurol 2021; 17 (5): 267‒284.