Of course, understanding where the pain of migraines come from does not explain why someone gets migraines in the first place or why one gets a migraine on any particular day. There is some evidence that there is a migraine generator. This is based upon some patients developing "migraine like" headaches after implantation of neural stimulators for chronic pain and one patient who was observed during a spontaneous migraine during a time that she was being studied in a special type of scanner.

I like to think about a migraine threshold in those patients who are susceptible to migraines. Each day we wake up and if we are not having a migraine, we are below our individual migraine threshold. As the day goes on, certain things happen that moves us closer or further from our migraine threshold. These things vary from person to person but may include stress, eating certain foods, sensing different smells, seeing certain patterns of lights, and many things which we have not yet identified. If you cross over your threshold, you then trigger your migraine and the events leading to neurogenic inflammation occur.

Migraine Prevention and Prophylactic Treatment of Migraine