Fig. 1. Temporal relationship between ovarian hormones and occurrence of catamenial seizures during the menstrual cycle.

The upper panel illustrates the strong relationship between seizure frequency and estradiol/P levels. The lower panel illustrates the three types of catamenial epilepsy. The vertical gray bars (left and right) represent the likely period for the perimenstrual (C1) type, while the vertical gray bar (middle) represents the likely period for the periovulatory (C2) type. The horizontal dark gray bar (bottom) represents the inadequate luteal (C3) type that likely occur starting early ovulatory to menstrual phases. In general, the female reproductive cycle is estimated to last 29 days. Day 1 is the onset of menstruation, and ovulation occurs 14 days before the onset of menstruation. The menstrual cycle is divided into four phases: (i) menstrual phase, days -3 to +3; (ii) follicular phase, days +4 to +9; (iii) ovulatory phase, days +10 to +16; and (iv) luteal phase, days +17 to -4. The early follicular phase is associated with low levels of estrogens and P. The synthesis and secretion of estrogens and P from the ovaries is controlled primarily by the hypothalamic GnRH and pituitary gonadotropins, FSH and LH. As ovulation approaches, the level of estrogen rises and triggers the release of a large surge of LH leading to ovulation. Following ovulation, the ruptured follicle luteinizes and forms a corpus luteum that secretes P and estrogen. Estradiol is secreted in the second half of the follicular phase and increases to a peak at midcycle, while P is elevated during the luteal phase and declines before menstruation begins. The neurosteroid AP is increased in parallel to its precursor, P (Reddy, 2009).