Approximately half of the women of childbearing age who have epilepsy report an increase in seizures related to their menstrual cycle. Seizures occurring predominantly during a particular part of the menstrual cycle are referred to as catamenial epilepsy. Seizures in catamenial epilepsy usually occur at predictable times:

  • Just before and/or at the onset of bleeding or menses (day 1)
  • At ovulation (midcycle or day 14, in a woman with a 28 day cycle)
  • During the second half of the cycle (days 15-28), particularly in women with abnormal cycles

Why are seizures more likely to occur around the time of menstruation?

This is most likely due to the specific changes in sex hormone levels just before and during menstruation. The two main hormones, estrogen and progesterone, can easily cross the barrier that separates the blood and the brain (the blood-brain barrier), and affect brain cells differently. Estrogen, which is responsible for the onset of bleeding and for ovulation, tends to be proconvulsant; that is, estrogen may lower seizure thresholds making seizures more likely. Meanwhile, progesterone, responsible for keeping the uterine lining rich in preparation for a fertilized egg, has anticonvulsant properties and might be relatively protective against seizures.

How can catemenial epilepsy be controlled?

Control of seizures that occur mainly around the time of menstruation remains a difficult problem. For women who have regular menstrual cycles, a slight increase in the dosage of the antiepileptic drugs before the time of increased seizure frequency may be helpful. Some doctors also recommend taking an additional medication during a woman’s vulnerable time. Acetazolamide (Diamox), a mild diuretic with possible antiepileptic properties, has often been used, but its efficacy in catamenial epilepsy has been disappointing. It seems to be more helpful in diminishing the water retention that occurs in the premenstrual period. Some physicians recommend lorazepam (Ativan), a drug similar to diazepam (Valium), but like Valium it often causes sleepiness, slowed thinking and incoordination. In more recent years, use of progesterone and high progesterone containing birth control pills has been more popular, but the efficacy and safety of hormonal therapy for this type of epilepsy remain to be established. Also, it appears that a woman’s natural progesterone has more of an anticonvulsant effect than the synthetic progesterone in these therapies.