Cyclical excitability of the motor cortex in patients with catamenial epilepsy: A transcranial magnetic stimulation study

Purpose: The pathophysiology of catamenial epilepsy is still unclear. Therefore, we investigated the cortical excitability of women with catamenial epilepsy during different phases of the menstrual cycle. Methods: Using transcranial magnetic stimulation, six patients suffering from catamenial epilepsy were investigated during ovulatory cycles. On days 8, -14, -7 and 2 of the cycle (day 1 being the first day of menstrual bleeding), resting motor threshold (RMT), cortical silent period (CSP), intracortical inhibition (ICI) and intracortical facilitation (ICF) were investigated. The non-parametric Friedman-test for multiple comparisons and Wilcoxon signed rank test were used for statistical analysis. Results: Five patients suffered from focal epilepsy (three right hemispheric, one bitemporal, one unknown origin) and one patient had idiopathic generalized epilepsy. All patients experienced perimenstrual seizure clustering and two also showed an increased seizure frequency during the luteal phase. In the right hemispheres there was a significant change of CSP duration in the course of the menstrual cycle (chi(2) = 8.3, P = 0.041), due to a shorter CSP during the luteal phase (Z = -2.0, P = 0.043) and menstruation (Z = -2.2, P = 0.028) as compared to the follicular phase. There was no significant variation of CSP in the left hemispheres. RMT, ICI and ICF showed no significant changes in the course of the menstrual cycle. Conclusions: The CSP changes suggest a decreased inhibition involving GABA-ergic neurotransmission during the luteal phase and menstruation. These TMS alterations correlated with the clinical course of the epilepsies and were found in the hemispheres containing the majority of the epileptogenic zones. (C) 2006 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.