CALCA and migraine disorder: A study using transcranial Doppler sonography, CGRP infusion induced a greater vasodilatatory reponse in the posterior circulation in migraine with aura than in migraine without aura patients; the authors suggest that this could favour CSD assuming that CGRP would dilate chiefly the proximal arteriolar segments while the distal segments would constrict due to local hyocapnia to maintain a constant cerebral blood flow, a hypothesis that needs to be proven [11].