I would recommend going to the American Headache Society website. You should get some good basic information there.
Pull up some RECENT review articles on pubmed, written by established headache specialists. The difference in quality and accuracy of information that you receive from a headache specialist and a neurologist is generally huge. Unfortunately, migraine is just not strongly emphasized during residency. It is not until going into a headache fellowship where one learns about migraine extensively.
There are many theories that attempt to explain the pathophysiology of migraine. The reality is, it is probably a combination of these theories and theories that are yet to be formulated. "Migraine science" is in it's infancy as there are few animal models (i.e. you can't ask a mouse if it is having head pain and migraine does not show up on EEG, MRI, etc.) and not very many researchers (in relative terms) conduct research on the topic.
Look up Robbins Headache Clinic. They post many articles.
You've picked a difficult but important topic to write on.
Best of luck!