The Effects of Different Phases of Menstrual Cycle on Blood Levels of Antiepileptic Drugs and Electroencephalography in Adolescent Girls with Idiopathic Epilepsy

Aim: Increased seizure activity may be observed in certain phases of menstrual cycle due to unknown reasons. Menstrual cycle-related seizures are defined as catamenial seizures. Molecular mechanisms involved in the etiology of catamenial epilepsy (CE) are not precisely known, yet. In this study, based on the hypothesis that altered serum antiepileptic drug (AED) levels can be a factor, we aimed to investigate serum AED levels and electroencephalography (EEG) results from different phases of menstrual cycle in adolescent girls with idiopathic epilepsy. Materials and Methods: A total of 27 adolescent girls (mean age: 15.4±1.3 years) who were admitted to Karadeniz Technical University, Faculty of Medicine, Department of Pediatrics, Division of Pediatric Neurology, diagnosed idiopathic epilepsy and were menstruating, were included in the study. Serum AED, estradiol (E2) and progesterone (Pg) levels at the menstrual and late luteal phases of the menstrual cycles were examined and EEG was performed. Results: Sixteen patients were on valproate (VPA), nine patients were on levetiracetam (LEV), and three patients were on carbamazepine (CBZ) treatment. Due to small sample size, no statistical comparison was performed for CBZ. There was no significant difference in the VPA and LEV levels in the menstrual and luteal phases (p>0.05). The patients were classified according to the ovulatory and anovulatory cycle, only the number of patients in the anovulatory cycle was found to be sufficient for the statistical analysis. There was no significant difference in the VPA and LEV levels in different time periods (p> 0.05). In patients who gave blood samples on the first day of the menstrual cycle, when menstrual fluid retention was expected, serum VPA (n=12) levels at two phases were not found to be statistically significantly different (p>0.05). Two patients were diagnosed with CE. One of these patients, 57% reduction was seen in the CBZ level during the menstrual phase compared to the luteal phase. In addition, EEG showed pathological findings in the menstrual period. In the remaining patients, EEG findings in both phases of the menstrual cycle were normal. Conclusion: Our study results showed no significant changes in serum AED levels at the menstrual and luteal phases in adolescent girls with idiopathic epilepsy using VPA or LEV. However, in one of the patients with CE, reduced CBZ levels during menstrual cycle and presence of pathological findings in EEG were interesting. Further studies are required to confirm these findings in patients with CE.