Menstrual Headache in Women with Chronic Migraine Treated with Erenumab: An Observational Case Series.

Background: We aimed to assess the differences between menstrual and non-menstrual headache in women with chronic migraine treated with erenumab. Methods: We included fertile women from a single center. Patients were defined as responders to erenumab if reporting a ≥50% decrease in monthly headache days, as compared to pre-treatment for more than half of the treatment period. Premenstrual days were defined as the two days preceding menstruation, while menstrual days were defined as the first three days of menstruation. Results: We included 18 women (11 erenumab responders and 7 erenumab non-responders) contributing to a total of 103 menstrual cycles and 2926 days. The proportion of headache days was higher in menstrual than in premenstrual and non-menstrual days in erenumab responders (34.4% vs. 14.8% vs. 16.3%, respectively; p < 0.001) and in erenumab non-responders (71.4% vs. 53.6% vs. 48.3%, respectively; p < 0.001). Headache days with ≥2 acute medications were higher in menstrual than in premenstrual or non-menstrual headache days in erenumab non-responders (p = 0.002) but not in erenumab responders (p = 0.620). Conclusions: Our data suggest that migraine is more frequent during than outside menstrual days even in women treated with erenumab.