Arterial mechanisms in the pathophysiology of migraine headache-implications for modern therapy

Studies of the cephalic vascular system have markedly contributed towards an understanding of the mechanisms of migraine pain. Whereas cerebral blood flow changes, and thereby changes in the arterioles, correlate poorly with migraine headache, abnormal regulation of the large cranial arteries seems to play a significant role in relation to migraine pain. Thus, vasodilation of extra- and intracranial conductance arteries has been described both during spontaneous migraine attacks and during experimentally provoked vascular headaches. Whether dilation of these arteries is the key mechanism of migraine nociception or is merely associated with another more important nociceptive mechanism remains to be shown. Studies of vascular regulatory mechanisms have not only pointed towards a possible locus of migraine pain, but have also been helpful in demonstrating a new molecular mechanism of migraine-the key effect of the small messenger molecule nitric oxide. It is likely that nitric oxide is the most important molecule responsible for the induction of migraine attacks.