Menstrually-Associated Migraine

A condition known as "true menstrual migraine" has been defined, rather strictly, as migraine occurring only in the time frame of the two
days before bleeding begins, and the three days after, and at no other time of the month. Only 10–14% of women experience true
menstrual migraine. Up to 60% of women with migraine, however, experience menstrually-associated migraine, as mentioned.

Why does migraine worsen at the time of your menstrual cycle? There are a number of complex biological reasons that this might be so.

Estrogen withdrawal is one such reason. Estrogen levels peak each month at ovulation, and then decline, falling to their lowest levels just
before menstrual bleeding begins, usually on day −1, or the day before your period starts.

Estrogen and progesterone affect a variety of neurotransmitters in the brain, and can therefore affect susceptibility to migraine. In animal
studies, both hormones can exhibit variable effects, depending on which part of the brain is being studied. The overall effect of all the
changes is still being worked out. We do know from studies done in the 1970s that the drop in estrogen at the time of menstruation
induces migraine, but the drop in progesterone does not. A more recent study has shown that at other times in the menstrual cycle when
both estrogen and progesterone levels are higher, there are low levels of migraine severity and disability.

Another chemical involved is prostaglandin, an inflammatory neurotransmitter also found to be present in migraine attacks. Prostaglandin
reaches peak levels perimenstrually. Nonsteroidal anti-inflammatory agents can be used as anti-prostaglandin agents.