Fig. (1). Role of the trigeminal neuron in the migraine attack Attack eliciting factors at the sub-cortical level provoke dilatation of cranial vessels with the activation of trigeminal sensory afferent endings and a consequent neurogenic inflammation process, due to the release of CGRP and SP or NK-A.BK: bradykinin; NO: nitric oxide; CGRP: calcitonin gene-related peptide; SP: substance P; NK-A: neurokinin A.