For decades, clinicians have recognized that reproductive hormones modulate neuronal excitability. Consequently, catamenial epilepsy has been widely diagnosed when female patients report seizure exacerbations synchronized with their menstrual cycle. Neuroactive steroids, particularly estrogens and progesterone metabolites like allopregnanolone, exert opposing actions on GABAergic and glutamatergic pathways. However, emerging chronobiological evidence indicates that seizure susceptibility follows intrinsic multiday periodicities regardless of biological sex. A comprehensive scoping review has evaluated existing diagnostic standards, highlighting significant methodological limitations across historical literature. Therefore, neurologists and gynecologists must re-examine the criteria used to differentiate genuine endocrine-driven exacerbations from non-hormonal cyclical rhythms.

Understanding Catamenial Epilepsy and Diagnostic Challenges

Clinicians generally define catamenial epilepsy as a cyclical increase in seizure frequency linked to specific phases of the menstrual cycle. Historically, researchers described three classic patterns: perimenstrual (C1), periovulatory (C2), and inadequate luteal phase (C3). These patterns correlate seizure spikes with rapid progesterone withdrawal or high estrogen-to-progesterone ratios. Despite these clear physiological models, real-world clinical application remains remarkably inconsistent. Many practitioners rely entirely on subjective recall or brief diary entries rather than objective hormonal assays. Consequently, the reported prevalence of this condition varies dramatically from 10% to over 70% across published cohorts. This enormous disparity suggests that existing diagnostic thresholds lack specificity. Furthermore, without standardized verification, clinicians risk attributing any roughly monthly seizure cluster entirely to ovarian cycles.

Findings from the Scoping Review on Seizure Cyclicity

To investigate the consistency of diagnostic approaches, investigators performed a systematic scoping review across major biomedical databases, including MEDLINE and EMBASE. They screened 233 articles and identified 70 primary studies specifically investigating menstrually related seizure patterns. Strikingly, 52.9% of these studies failed to define or specify the diagnostic criteria utilized to establish the condition. In addition, 47.1% of the included literature did not report the duration of baseline tracking before assigning a diagnosis. Among studies that did report monitoring duration, nearly one-third evaluated patients for three months or fewer. Because menstrual cycles and seizure frequencies naturally fluctuate from month to month, such brief evaluation windows cannot reliably confirm true endocrine causality. Thus, current scientific literature demonstrates significant fragmentation and methodological fragility.

The Confounding Role of Multidien Seizure Rhythms

The discovery of endogenous multidien rhythms represents a major paradigm shift in modern epileptology. Continuous electroencephalographic monitoring through implanted responsive neurostimulation devices has revealed that cortical excitability fluctuates over multi-day, circatrigintan (approximately monthly) cycles. Crucially, these 20-to-30-day rhythms occur with equal frequency and robustness in men, postmenopausal women, and children. In the scoping review, literature evaluating multidien cycles (33 studies) demonstrated an average recording duration of 24 months, utilized objective multimodal recordings, and incorporated rigorous significance testing. Because an individual can harbor an innate 28-day multidien cycle that randomly aligns with a 28-day ovarian cycle, distinguishing between the two requires sophisticated mathematical phase analysis rather than simple visual diary inspection.

Clinical Risks of Misdiagnosis and Inappropriate Hormonal Therapy

Relying on inadequate diagnostic criteria exposes patients to significant clinical risks. When physicians misclassify non-specific multidien seizure rhythms as hormonally mediated exacerbations, patients often receive unnecessary endocrine interventions. These therapies include cyclic oral progestins, medroxyprogesterone acetate injections, gonadotropin-releasing hormone agonists, or synthetic neurosteroids. Although hormonal agents benefit patients with true neuroendocrine sensitivity, they carry notable adverse effects, including bone mineral density loss, mood disturbances, thromboembolic risks, and metabolic dysfunction. Furthermore, attribution bias may delay the optimization of standard anti-seizure medications or evaluation for surgical therapies. Therefore, physicians must carefully weigh the evidence before altering endocrine function in patients with drug-resistant epilepsy.

Rethinking Diagnostics: Moving Beyond Short-Term Diaries

Addressing these diagnostic pitfalls requires a modern chronobiological approach to seizure tracking. Clinicians should encourage patients to maintain prospective, digital tracking diaries spanning at least six consecutive menstrual cycles. Whenever possible, objective biological confirmation—such as mid-luteal serum progesterone measurements or urinary luteinizing hormone surge kits—should accompany symptom logs to verify ovulatory status. In addition, future clinical trials must incorporate advanced statistical modeling and circadian-infradian rhythm analytics. By combining long-term electrophysiological data with precise endocrine profiling, clinicians can clearly distinguish genuine menstrual vulnerability from underlying multidien periodicity, ensuring tailored and effective therapeutic management.

Frequently Asked Questions (FAQs)

What distinguishes catamenial epilepsy from other cyclical seizure patterns?

Catamenial epilepsy specifically results from neuroendocrine fluctuations, where changes in estrogen and progesterone alter cortical excitability during distinct menstrual phases. In contrast, general multidien rhythms are intrinsic biological oscillations in brain excitability that span multi-day or monthly cycles. These multidien cycles occur independently of sex hormones and appear equally across men, children, and women.

How many months of prospective tracking are necessary to confirm a diagnosis?

Experts recommend tracking seizures and menstrual cycles prospectively for at least four to six consecutive cycles. Brief tracking periods of one to three months often produce false-positive diagnoses because non-menstrual monthly seizure rhythms can temporarily align with menstrual periods. Extended tracking ensures that statistical correlation remains robust over time despite natural cycle variability.

What are the primary treatment options for verified catamenial seizure exacerbations?

First-line management involves optimizing baseline anti-seizure medications. For patients with verified perimenstrual exacerbations, clinicians may prescribe intermittent pulse therapy with benzodiazepines such as clobazam or acetazolamide during high-risk days. Hormonal interventions, including cyclical progesterone therapy, oral contraceptives, or gonadotropin-releasing hormone analogues, serve as adjunctive therapies when non-hormonal strategies fail.

Disclaimer: This content is for informational and educational purposes only and should not be construed as medical advice. Always consult a qualified healthcare professional regarding any medical condition or treatment decision. Refer to the latest local and national guidelines for clinical practice.

References

1. Wong V et al. Monthly or menstrual? A scoping review of catamenial epilepsy and non-menstrual seizure rhythms. Epilepsia. 2026 Aug 17. doi: 10.1002/epi.70424. PMID: 42606528.
2. Herzog AG, Klein P, Ransil BJ. Three patterns of catamenial epilepsy. Epilepsia. 1997;38(10):1082-1088.
3. Baud MO, Kleen JK, Mirro EA, et al. Multi-day rhythms modulate seizure risk in epilepsy. Nat Commun. 2018;9(1):88.
4. Reddy DS. Neurosteroids and catamenial epilepsy. Int Rev Neurobiol. 2020;154:147-175.