Epilepsy and the Menstrual Cycle

Some women with epilepsy have seizures which are triggered by hormonal changes during the menstrual cycle. This is known as catamenial epilepsy.


Hormones and the Menstrual Cycle

During a woman’s menstrual cycle, the levels of different hormones in her body change. Two of these hormones, oestrogen and progesterone, affect the excitability of the brain, especially in the temporal and frontal lobes of the brain. Oestrogen has a convulsant effect, so it can make seizures more likely to occur. Progesterone has an anticonvulsant effect, so it can make seizures less likely to occur.

In order to understand how your menstrual cycle may affect your epilepsy, it may be helpful to have a basic understanding of the menstrual cycle.

The majority of women have a menstrual cycle which lasts 25-35 days. The average cycle lasts for 28 days. The first day of a woman's period is counted as the beginning of the cycle. During the first half of the cycle, the body produces oestrogen.

Around 14 days after the first day of the period, when the level of oestrogen is at its highest, an egg is released from the ovary (the exact timing can vary greatly from woman to woman). This is called ovulation. After ovulation, the body starts to produce progesterone as well as oestrogen.

If pregnancy does not occur, the body slowly stops producing hormones, so the levels of oestrogen and progesterone fall and menstruation occurs. This is the beginning of a new cycle.


Patterns of Catamenial Epilepsy

In women who have regular menstrual cycles, the oestrogen levels are higher than progesterone levels leading up to ovulation and immediately before menstrual bleeding. Therefore, as oestrogen has a seizure provoking effect, this can cause two patterns of catamenial epilepsy:

  • Seizures which occur before or during the first few days of the menstrual cycle
  • Seizures which occur at the time of ovulation (when the level of oestrogen is at its highest).

Some women have abnormal menstrual cycles and do not ovulate regularly or do not ovulate at all. This may mean that they do not produce enough progesterone (which has an anticonvulsant effect (during the entire second half of the menstrual cycle. This is the third recognised pattern of catamenial epilepsy:

  • An increase in seizures during the entire second half of the menstrual cycle.

Effect of Anti-epileptic Drugs on Catamenial Seizures

Oestrogen and progesterone are metabolised (broken down) by the same enzymes in the liver that metabolise many of the common anti-epileptic drugs (AEDs) (phenytoin, carbamazepine, oxcarbazepine, phenobarbitone, primidone, topiramate and possibly ethosuximide).

When the levels of oestrogen and progesterone are low, such as before menstruation, there are more liver enzymes available to metabolise the AEDs. This means the AEDs are broken down more quickly than at times when the hormone levels are high, such as after ovulation.

When AEDs are broken down quickly, this means that the levels in the blood are lower than at other times of the menstrual cycle. This can increase the risk of seizures occurring. On the other hand, when the AEDs are broken down slowly, the levels in the blood are higher than other times. This offers more protection against seizures.
Effect of premenstrual tension

Many women find that their periods affect their mood, especially in the days leading up to menstruation. This is known as premenstrual tension (PMT). Stress and anxiety are common symptoms of PMT and these are also well-recognised triggers for seizures. For this reason, having PMT may increase the risk of seizures.

Many women experience water retention around the time of their period and there is some evidence to suggest that changes in the fluid balance of the body may make seizures more likely.

Recognising Catamenial Seizures

If you suspect that your seizures may be connected to your menstrual cycle, the easiest way to try to identify this is by keeping a record of all your seizures and the dates of your periods in the same diary. When this information has been recorded for a few months, you can review this with your doctor or epilepsy specialist nurse, to see if any seizure patterns can be identified.

It would also be helpful to keep a record of any other factors which may trigger your seizures in the diary, such as lack of sleep, missing medication, lack of food, stress or alcohol consumption. This can be helpful for identifying other reasons for your seizures.

Treatment for Catamenial Epilepsy

Modern treatment for catamenial epilepsy usually involves the drug clobazam. This drug is taken at specific times during the cycle, unlike usual anti-epileptic medication, which has to be taken continuously.

Research is also being carried out into the effect of changing women’s hormones at various times during the menstrual cycle, for example, by taking progesterone supplements. However, studies that have been carried out into this so far have had disappointing results.

If you feel that your seizures are affected by your menstrual cycle, it is advisable to seek advice from your GP, who may refer you to a neurologist with an interest in epilepsy, if they feel this would be helpful.