The extracranial vascular theory of migraine--a great story confirmed by the facts.

Over the years, there has been a considerable amount of controversy as to whether the vascular component of migraine pain arises from the intracranial or the extracranial vessels or both. Some have even questioned whether vasodilatation even plays a significant role in migraine pain and have described it as an unimportant epiphenomenon. In this review, evidence is presented that confirms (1) vasodilatation is indeed a source of pain in migraine; (2) this dilatation does not involve the intracranial vasculature; (3) the extracranial terminal branches of the external carotid artery are a significant source of pain in migraine.