The menstrual cycle can significantly influence seizure activity in women who have epilepsy. This connection arises because the primary female sex hormones, estrogen and progesterone, directly interact with the brain’s electrical signaling pathways. These natural fluctuations in hormone levels throughout the monthly cycle can increase or decrease the excitability of brain cells, thereby altering a woman’s susceptibility to seizures.
Defining Catamenial Epilepsy
The medical term for this phenomenon is Catamenial Epilepsy (CE), which describes a pattern where seizure frequency is noticeably exacerbated during particular phases of the menstrual cycle. It is not considered a separate type of epilepsy but rather a hormonal influence on an existing seizure disorder. The term “catamenial” originates from the Greek word for “monthly.”
This pattern is relatively common, affecting approximately 40% to 50% of women of reproductive age who have epilepsy. Diagnosis requires a consistent, periodic increase in seizure frequency that aligns with the hormonal shifts of the menstrual cycle. Identifying this pattern is important because it often indicates that a woman’s seizures may be resistant to standard anti-epileptic medications alone.
Hormonal Influence on Neuronal Activity
The underlying mechanism for Catamenial Epilepsy involves the opposing effects of estrogen and progesterone on brain excitability. Estrogen is generally considered pro-convulsant, increasing the likelihood of a seizure. It promotes the activity of glutamate, the main excitatory neurotransmitter, and decreases the effect of GABA, the brain’s primary inhibitory messenger.
Conversely, progesterone is anti-convulsant. Progesterone enhances the function of the GABA-A receptor, boosting the brain’s natural inhibitory signaling. This calming effect raises the seizure threshold, making a seizure less likely to occur.
The key factor influencing seizure risk is the fluctuating ratio between the two hormones, not the absolute level of one. A higher ratio of estrogen to progesterone creates increased neuronal excitability, making the brain more prone to abnormal electrical discharges.
Identifying High-Risk Cycle Phases
Catamenial Epilepsy is categorized into three distinct patterns based on when the seizure increase occurs within a typical menstrual cycle. Accurately identifying a woman’s specific pattern requires careful charting of seizure occurrences alongside menstrual cycles for at least two to three months.
Type 1: Perimenstrual Pattern
The most common pattern is Type 1, where seizures increase just before and during the first few days of menstruation. This exacerbation is triggered by the rapid withdrawal of both estrogen and progesterone following the collapse of the corpus luteum.
Type 2: Periovulatory Pattern
Type 2 involves a seizure increase around the time of ovulation, typically mid-cycle. This is linked to the peak in estrogen that occurs before the egg is released, while progesterone levels are still low. The resulting high estrogen-to-progesterone ratio creates a peak in neuronal excitability.
Type 3: Anovulatory Pattern
The third pattern, Type 3, occurs during an anovulatory cycle, meaning no egg is released. Since the body does not produce progesterone during the second half of the cycle, seizures increase throughout the entire luteal phase due to the sustained low level of progesterone.
Targeted Treatment Strategies
Management of Catamenial Epilepsy focuses on stabilizing the hormonal environment or using anti-epileptic medications specifically during the high-risk phases.
One common approach involves intermittent therapy, where the dosage of a woman’s regular anti-epileptic drug (AED) is temporarily increased, or a fast-acting AED is added, only during the identified vulnerable period. Certain drugs have been used on a pulsed basis, starting a few days before the expected seizure increase and continuing through the at-risk phase.
Hormonal therapies are highly targeted, especially for patterns driven by progesterone withdrawal (Type 1 and Type 3). Cyclic progesterone supplementation is often administered during the second half of the cycle to prevent the sharp premenstrual drop in the hormone. This approach can significantly reduce seizure frequency.
Another option is the use of hormonal contraceptives administered continuously to suppress the entire menstrual cycle and prevent hormonal fluctuations. Treatments that induce amenorrhea, such as injections, can also be effective. Lifestyle factors like consistent sleep and stress reduction are also important during high-risk phases to maintain a stable seizure threshold.