Vascular head pain: a neurobiologist's approach.

Cephalic blood vessels are invested with a dense network of perivascular fibers of diverse origin. A proportion of these fibers arise from trigeminal neurons and contain chemicals which have vasodilating and pro-inflammatory properties. Evidence suggests that these trigeminovascular neurons may influence both vascular function and neurophysiological activity within the brain. The trigeminovascular system may thus represent a (bi-directional, brain-vessel, vessel-brain) final common pathway for the actions of many chemical, mechanical and neural influences which may have important consequences for the pathogenesis and treatment of headache.