ABSTRACT
Circadian rhythms have marked effects on expression of epilepsy, influencing the timing of occurrence of seizures and the characteristics of interictal epileptiform discharges (IEDs). Circadian rhythms are not a singular entity but involve many systems within and without the central nervous system. Therefore, a circadian influence is not likely a single, unified mechanism. Rather, circadian rhythms are better thought of as endogenously mediated, excitatory, and inhibitory influences that vary with time of day and dynamically compete with other seizure precipitants to elevate or depress seizure threshold. In this chapter, I review basic concepts of chronobiology, the organization of the circadian timing system, the effects of epilepsy and seizures on circadian rhythms, and the influences of circadian rhythms on the timing of seizures.
