Catamenial epilepsy: in search of a clinical entity and its prevalence.

The prevalence of catamenial epilepsy has been difficult to determine for several reasons, including menstrual cycle variability and randomness of seizure occurrence, a high prevalence of seizure clustering in males and nonmenstruating females with epilepsy, and the lack of a definition of catamenial epilepsy in previous studies. Recently, a definition describing three distinct patterns that may provide a sensible nomenclature for future research on catamenial epilepsy has been proposed, and it may provide standardized criteria for inclusion in catamenial epilepsy studies. Such a definition should allow estimates of true prevalence of this disorder to be more precise and prospective treatment trials to be designed.