Distribution of seizures across the menstrual cycle in women with epilepsy

The purpose of this study was to determine whether seizure frequency and cycle days with seizure occurrence vary across the menstrual cycle. The subjects were the first 100 women with intractable focal onset seizures, 13-45 years old, who completed the baseline phase of the National Institutes of Health (NIH) Progesterone Trial. Each subject recorded seizures and menses during a 3-month baseline phase. Data consisted of (1) seizure numbers for each cycle day and (2) cycle days with seizure occurrence. Statistical comparisons of seizure frequency and days with seizures were performed using generalized estimating equation one-way analysis of variance (ANOVA) and logistic regression followed by pairwise multiple comparisons of days based on the least square means. Seizure numbers and cycle days with seizure occurrence varied across the menstrual cycle. There was an approximately twofold difference between the highest (day 1) and lowest (day -8) values for both seizure frequency and days with occurrence. The demonstration of variation in seizure frequency and cycle days with seizure occurrence across the menstrual cycle, as well as identification of specific days that have substantially higher or lower frequencies than other days, supports the existence of catamenial epilepsy.