Circalunar and ultralunar periodicities in women with partial seizures.

Purpose: Little consensus exists for the definition of catamenial epilepsy. Few studies have evaluated the periodicity of seizures to test the hypothesis that seizures in women have periodic patterns of occurrence independent of a priori hormonal considerations. In the present study, we determined seizure periodicity according to a "menstrual clock" provided by a common phase marker of the onset of menses.

Methods: Seizure and menstrual diaries of approximately 3 months duration were obtained from women enrolled in a trial of hormonal therapy for localization-related epilepsy. Midluteal progesterone levels identified ovulatory (>or=5 ng/ml, OC) from anovulatory cycles (AC). Individual cycles were normalized to a common phase and period (day 0 = menses onset, intervening days = 28 bins). Periodicity of combined data was estimated with cosinor-nonlinear least squares analysis. Best-fit rhythms were estimated with 95% confidence limits.

Results: 100 patients provided 3344 seizures within 293 cycles (77% OC, 20% AC, indeterminate 3%). OC seizures displayed a circalunar rhythm with peak phase of occurrence at onset of menses. AC seizures also featured a circalunar rhythm that peaked at menses onset but also had ultralunar rhythms of approximately 14 and approximately 9 days.

Discussion: Seizures in women with epilepsy occur in circalunar rhythms. OC and AC seizures differ in seizure timing with the latter occurring in ultralunar rhythms in addition to the predominant circalunar rhythm. This finding supports the existence of catamenial epilepsy and differences in patterns of seizure occurrence between OC and AC.