Catamenial Epilepsy

When seizure risk repeatedly changes with the menstrual cycle

Catamenial epilepsy describes a pattern in which seizures become more frequent or more likely during particular phases of the menstrual cycle. It is not a separate seizure type or epilepsy syndrome. It is a cyclical pattern superimposed on an existing epilepsy.

Research suggests that menstrual-related seizure worsening is common, but estimates vary depending on how catamenial epilepsy is defined and how carefully cycles and seizures are recorded. A Cochrane review notes that around 40% of women with epilepsy may experience a catamenial pattern.

Why can the menstrual cycle affect seizures?

Ovarian hormones can influence neuronal excitability.

Progesterone and its neuroactive metabolites, especially allopregnanolone, generally enhance inhibitory GABA-related signalling. Oestrogen can have more complex and sometimes pro-excitatory effects.

The important point is not that one hormone is always “good” and another always “bad”. Seizure susceptibility can change as hormone concentrations rise and fall across the cycle, and the effect differs between individuals and epilepsy types.

The three recognised catamenial patterns

Three commonly described patterns are used in research and clinical practice:

C1 — perimenstrual: seizures increase around menstruation, typically from several days before bleeding begins through the first few days of the period.
C2 — periovulatory: seizures increase around ovulation.
C3 — luteal or inadequate-luteal-phase pattern: seizure risk increases during the latter part of cycles in which ovulation or progesterone production is inadequate.

Not everyone fits neatly into one category. Cycles can be irregular, ovulation can vary from month to month, and seizure frequency itself may fluctuate for reasons unrelated to hormones.

The C1 perimenstrual pattern

The best-known pattern is a rise in seizures around menstruation.

One proposed mechanism is the rapid fall in progesterone and its GABA-enhancing metabolite allopregnanolone immediately before menstruation. Experimental work suggests that withdrawal from progesterone-derived neurosteroids can increase neuronal excitability.

This biological model is plausible, but it does not mean that every seizure occurring during a period is hormonally caused.

The C2 periovulatory pattern

Some people experience a seizure increase around ovulation.

This has been linked to the pre-ovulatory rise in oestrogen relative to progesterone, although the exact mechanism in humans is less certain than simple “high oestrogen equals seizures”.

The menstrual cycle affects several systems simultaneously, including sleep, temperature, stress, fluid balance and medication routines, which can also modify seizure threshold.

The C3 luteal pattern

In anovulatory cycles or cycles with inadequate progesterone production, the expected progesterone rise after ovulation may be reduced.

This can create a longer period in which the normal progesterone-related inhibitory effect is relatively weak.

C3 is therefore usually discussed in relation to anovulatory or inadequate-luteal-phase cycles rather than ordinary regular cycles.

How is catamenial epilepsy diagnosed?

There is no single blood test, EEG pattern or MRI finding that diagnoses catamenial epilepsy.

The foundation is a seizure-and-menstrual diary kept across multiple cycles.

Useful records can include:

first and last day of menstrual bleeding;
date and time of every seizure;
seizure type;
missed or late medication doses;
sleep loss;
illness;
alcohol use where relevant;
unusual stress;
changes in contraception or hormone treatment.

A repeating pattern is more informative than one bad period or one seizure cluster.

Why memory alone can mislead

People naturally notice events that happen during memorable phases such as menstruation, but may undercount seizures at other times.

Prospective diaries reduce this recall bias.

They can also reveal a different pattern: for example, seizures may actually be clustering after nights of poor sleep that happen to coincide with menstrual symptoms rather than with the cycle itself.

Does catamenial epilepsy only affect focal epilepsy?

No.

Catamenial worsening has been described in both focal and generalised epilepsies, although much of the older research included large numbers of people with focal epilepsy.

The menstrual pattern therefore describes when seizures increase, not where they begin.

Does having catamenial epilepsy mean hormones caused the epilepsy?

No.

A person may have epilepsy because of a structural, genetic, immune, infectious or unknown cause and still show a menstrual-related change in seizure frequency.

The hormonal cycle modifies seizure susceptibility; it does not necessarily explain the underlying cause of the epilepsy.

Can seizure medication levels change across the cycle?

For some medicines, hormone-related physiological changes may alter drug handling, but this is not the main explanation for every catamenial pattern.

More commonly, the menstrual cycle changes brain excitability while the medication dose remains the same.

Any planned cyclic dose adjustment should therefore be made by the treating specialist rather than by changing medication independently.

Standard antiseizure treatment still matters

Before adding a catamenial-specific strategy, clinicians usually confirm that the person’s baseline epilepsy treatment is appropriate.

That includes checking seizure classification, adherence, sleep, drug interactions and whether the current antiseizure medication is suitable for the epilepsy type.

Catamenial treatment is generally an addition to good epilepsy management, not a replacement for it.

Intermittent treatment approaches

When cycles are regular and a vulnerable window is predictable, some specialists use short-term treatment only during the high-risk days.

Approaches described in the literature include intermittent clobazam, acetazolamide, temporary adjustment of an existing antiseizure medicine and hormonal treatment.

The evidence supporting many of these approaches is limited. The Cochrane review found no randomised controlled trials of the commonly used non-hormonal intermittent strategies.

Clobazam

Clobazam has historically been used intermittently around a predictable vulnerable phase, particularly the perimenstrual period.

Evidence comes largely from older, small studies rather than modern large randomised trials.

Intermittent use may sometimes be chosen to reduce continuous exposure and tolerance, but benzodiazepines can cause sedation and other adverse effects and must be prescribed carefully.

Acetazolamide

Acetazolamide has also been used for catamenial seizure worsening.

A small retrospective series reported a substantial seizure reduction in some patients, but the study was small and uncontrolled. Loss of benefit over time was also reported in a minority.

It is therefore an option sometimes discussed in specialist practice rather than a treatment supported by strong trial evidence.

Progesterone treatment

Natural progesterone has attracted considerable interest because progesterone-derived neurosteroids can enhance inhibitory GABA signalling.

However, clinical evidence is mixed.

The updated Cochrane review found low- to moderate-certainty evidence that progesterone was not clearly superior to placebo overall, although the trials were underpowered and important subgroup effects could not be excluded.

A 2023 systematic review reached a similar conclusion: uncontrolled studies often suggested benefit, but randomised controlled trials did not clearly demonstrate efficacy.

This is why progesterone should not be presented as a proven universal treatment for catamenial epilepsy.

Why some progesterone studies appeared more promising in C1

Subgroup analyses from the large NIH progesterone trial suggested that people with a strong perimenstrual C1 pattern may have responded better than those without a clear C1 exacerbation.

This finding helped shape later treatment discussions, but subgroup findings are not the same as definitive proof.

Further well-designed trials are still needed.

Hormonal suppression of the menstrual cycle

When cycles are irregular or intermittent treatment does not work, specialists may sometimes consider strategies that suppress ovulation or menstruation.

Options described in reviews include medroxyprogesterone or gonadotropin-releasing hormone analogues.

These approaches can affect fertility, bone health, cardiovascular risk and other aspects of health, so they require specialist gynaecological and neurological supervision.

Contraception can complicate the picture

Hormonal contraception can alter bleeding patterns and ovarian hormone cycling.

At the same time, some antiseizure medicines reduce the effectiveness of hormonal contraception, while oestrogen-containing contraception can substantially lower lamotrigine levels.

A seizure change after starting or stopping contraception may therefore reflect hormone effects, medication-level changes, or both.

See Hormones, Contraception & Pregnancy for the broader interaction issues.

Irregular periods make diagnosis harder

If cycles are irregular, predicting ovulation and defining C1, C2 or C3 windows becomes more difficult.

Conditions such as polycystic ovary syndrome, perimenopause, low body weight, endocrine disease and some medications can alter cycle regularity.

In these situations, a specialist may need to consider whether menstrual irregularity itself requires assessment rather than assuming every seizure fluctuation is catamenial.

Perimenopause

Perimenopause can produce irregular ovulation, fluctuating oestrogen and progesterone levels, sleep disruption and changing bleeding patterns.

For someone with previously predictable catamenial epilepsy, the pattern may therefore become less regular.

This is one reason menopause and epilepsy deserve their own assessment rather than simply extending a premenstrual treatment plan indefinitely.

What catamenial epilepsy is not

Catamenial epilepsy does not mean:

every seizure during menstruation is hormonal;
periods themselves cause epilepsy;
hormone treatment will necessarily work;
standard antiseizure medication should be stopped;
a seizure diary can replace specialist evaluation.

When should the pattern be reviewed?

Review is particularly useful when seizures repeatedly cluster in the same phase across several cycles, when a previously stable epilepsy changes after starting or stopping contraception, or when seizure worsening appears during puberty, after pregnancy or during perimenopause.

A specialist can then decide whether the pattern is strong enough to justify a cycle-specific treatment strategy.

The evidence gap

Catamenial epilepsy is clinically recognised, yet the treatment evidence remains surprisingly limited.

The Cochrane review identified only a small number of randomised hormonal trials and no randomised trials of several commonly used non-hormonal intermittent approaches.

This creates a gap between real-world specialist practice and the strength of published evidence.

It also means treatment should be individualised and described honestly: some approaches are biologically plausible and clinically used without being strongly proven by large trials.

The key distinction

Catamenial epilepsy is a reproducible pattern of seizure exacerbation linked to phases of the menstrual cycle.

It is not a seizure type, not a cause of epilepsy and not something that can be diagnosed from one difficult period.

The strongest evidence comes from careful prospective tracking across several cycles, followed by specialist interpretation of whether the pattern is genuinely hormonal and whether treatment should be adjusted during predictable vulnerable periods.

Sources and further reading

Evidence checked: September 2026.

This page is for general education and does not replace individual advice from an epilepsy specialist, GP, pharmacist or reproductive-health clinician.