Pure menstrual migraine
Documented and prospectively-recorded evidence over at least three consecutive cycles has confirmed that attacks occur exclusively on day 1 ± 2 (ie, days −2 to +3) of menstruation in at least two out of three menstrual cycles and at no other times of the cycle.
Menstrually-related migraine
Documented and prospectively-recorded evidence over at least three consecutive cycles has confirmed that attacks occur on day 1 ± 2 (ie, days −2 to +3) of menstruation in at least two out of three menstrual cycles, and additionally at other times of the cycle.
Source
Headache Classification Committee of the International Headache Society (IHS) (2013). The International Classification of Headache Disorders, 3rd edition (beta version). Cephalalgia 2013; 33: 9-807.