Migraines have no established cause, although they're assumed to be caused by aberrant brain activity that disrupts nerve signals, neurotransmitters, and blood vessels in the brain. Hormonal, emotional, physical, nutritional, environmental, and pharmaceutical factors have all been cited as probable migraine causes. Some women get migraines around the time of their menstruation, probably due to changes in hormone levels such as oestrogen.

from Times of India https://timesofindia.indiatimes.com/life-style/health-fitness/health-news/is-it-a-migraine-attack-why-many-people-fail-to-recognise-symptoms-and-dont-know-what-triggers-them/articleshow/90055140.cms