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Seizures Related to the Menstrual Cycle
Catamenial Epilepsy
An increase in seizure frequency around the time of menstruation (catamenial epilepsy) was first documented more than 100 years ago.
It is variously reported in 10% to 72% of women
Seizures are linked to menses because sex hormones alter the excitability of neurons in the cerebral cortex.
Estrogens can lower seizure threshold, resulting in an increase in the frequency of interictal spikes & seizures.
Progestins have the opposite effect and may protect against seizures.
Ovulation and Seizures
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The presence or absence of ovulation in any single menstrual cycle affects the likelihood of seizure, and women may exhibit different patterns of seizure exacerbation.
Ovulatory cycles display two distinct patterns.
First, seizures may increase a few days before menses and in the first 2 to 3 days of bleeding, perhaps precipitated by
the rapid decline in progesterone levels.
Second, seizure frequency may increase at the time of ovulation as a result of the rise in estrogen levels.
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Ovulatory Cycles Protect against Seizures.
Women with catamenial epilepsy there is a reduction in seizures during the luteal phase (days 17 to 24) of ovulatory cycles owing to the protection of increased progesterone levels.
With anovulatory cycles ( a cycle where the egg is not released), the progesterone-secreting corpus luteum is not formed and estrogen levels remain high. Anovulatory cycles are associated with a pattern of increased seizures during the entire second half of the menstrual cycle.
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Diagnosis of Catamenial Pattern
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To determine if a catamenial pattern is present, patients should be instructed to chart menses along with basal body temperature and seizures for several months.
A record of basal body temperature is useful in determining ovulation.
Progesterone levels can be measured on day 22 of the menstrual cycle (day 1 being the onset of menses). A progesterone level lower than 5 ng/mL on day 22 indicates an anovulatory cycle.
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Management of Catamenial Seizures
A supplemental daily dose of the maintenance antiepileptic drug at the expected time of seizure exacerbation
Acetazolamide a carbonic anhydrase inhibitor, has also been used but with limited success.
Hormonal manipulation is unconventional, but it may involve either increasing the level of progesterone or decreasing the level of estrogen
Any treatment with hormonal manipulation should be done in collaboration with a gynaecologist and in the presence of effective contraception.
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