Catamenial epilepsy links seizures to the menstrual cycle. Learn the three patterns, why it's underdiagnosed, and how cycle tracking transforms treatment.
You notice your seizures cluster around the same days each month. Your friends tell you it's a coincidence. Your GP shrugs. But the pattern keeps repeating, and after several months you're certain your cycle and your seizures are linked. You're not imagining it. You may have catamenial epilepsy — a recognised condition in which seizures correlate with specific phases of the menstrual cycle, affecting roughly one in three women with epilepsy of reproductive age.
The term "catamenial" simply means "monthly" — derived from the Greek for "month." Catamenial epilepsy refers to a pattern in which seizures consistently increase at certain points of the menstrual cycle. It isn't a separate type of epilepsy; it's a hormonal pattern overlaid on whatever underlying epilepsy you already have. Your seizures are the same kind they've always been. They just happen more often at predictable times.
The mechanism is hormonal. Estrogen tends to be pro-convulsant — it lowers the seizure threshold. Progesterone tends to be anti-convulsant — it raises the threshold. As your cycle moves through different ratios of these two hormones, your seizure susceptibility shifts. The three classical catamenial patterns map onto the three points where these hormones swing most dramatically.
Perimenstrual (C1) — seizures cluster in the days just before and during your period. This is the most common pattern and is driven by the rapid drop in progesterone that happens when the corpus luteum involutes. The high-progesterone, anti-seizure environment of the late luteal phase suddenly disappears, and seizures break through.
Periovulatory (C2) — seizures cluster around ovulation, in the middle of the cycle. This pattern is driven by the surge in estrogen that triggers ovulation. The brief spike of pro-convulsant estrogen lowers the seizure threshold for a few days.
Luteal (C3) — seizures increase throughout the second half of the cycle. This pattern is associated with anovulatory cycles, where ovulation doesn't occur and progesterone never rises to its protective level. Without the seizure-raising effect of progesterone, the entire luteal phase becomes vulnerable.
You may not fit neatly into one pattern. Some women have features of more than one. Others have a clear single pattern that's been visible their whole adult life. The only way to know which (if any) applies to you is to track both your seizures and your cycle for several months and look for the correlation.
Catamenial epilepsy should be obvious — and for some people it is. But it's persistently underdiagnosed for several reasons. Many neurologists don't routinely ask about menstrual cycles. Many women don't connect their seizures to their cycle until the pattern is unmistakable. Even when both parties suspect it, the only way to confirm the pattern is with consistent dual tracking — and the dual tracking rarely happens.
Without data, the conversation goes nowhere. "I think my seizures are worse around my period" is hard to act on. "Here's three months of logged data showing 80% of my seizures fall within the four days before menstruation" is a foundation for treatment changes. The difference between those two statements is just systematic logging.
Tip: If you suspect a hormonal pattern, log your period start and end dates alongside your seizures. Even rough cycle tracking is enough to make the pattern visible if it exists.
Once you start tracking seizures alongside your cycle, the picture clarifies fast. Within two to three cycles, you can usually see whether there's any correlation at all. By six cycles, the pattern (if it exists) is unmistakable. You can show your neurologist a chart that maps every seizure against every cycle phase — and that conversation goes very differently from one based on impressions.
This is exactly the kind of analysis that paper diaries can't reliably support. The data needs to be searchable, sortable, and aggregatable across many cycles. A digital seizure tracker captures both the time and the context of each episode in a way that makes hormonal pattern detection genuinely possible.
Confirmation of a catamenial pattern opens up specific treatment strategies that aren't relevant for non-hormonal epilepsy. These include:
None of these options is appropriate without first confirming the pattern. That's why the tracking is the critical first step.
If you're considering pregnancy, hormonal patterns become even more important. The dramatic hormonal shifts of pregnancy, postpartum, and breastfeeding all affect seizure frequency. Knowing your pre-pregnancy hormonal pattern gives your obstetric and neurology teams crucial baseline information. Pre-conception planning for epilepsy is significantly better when you have this kind of data.
Bring your tracked data to the appointment. Show your neurologist the correlation between your cycle and your seizures. Ask explicitly whether catamenial epilepsy fits your pattern. If they're not familiar with cyclical treatment options, ask for a referral to a specialist epilepsy clinic — many UK epilepsy centres now have specific women's epilepsy services.
You're not asking for a favour. You're presenting evidence and asking for treatment that fits the evidence. That's how good medicine works, and it starts with the data only you can collect.
Catamenial epilepsy is a hidden source of preventable seizures in many women's lives. It's underdiagnosed because the data needed to spot it is rarely collected systematically. Once it is, the diagnosis is usually straightforward and the treatment options are well-established. Tracking is the bridge between living with unexplained monthly seizures and getting the targeted treatment that addresses the actual cause.
If you've ever wondered whether your cycle and your seizures are connected, the answer is probably worth investigating. And the investigation costs nothing more than consistent logging.
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