Estimation of cerebrovascular reactivity in migraine without aura

The nature and role of vascular abnormalities in migraine are controversial. In this study we evaluated cerebrovascular reactivity to hypercapnia in patients suffering from migraine without aura with unilateral headache. Using bilateral transcranial Doppler ultrasound, we studied the changes of flow velocity after hypercapnia in the anterior, middle, and posterior cerebral arteries of 16 migraine patients and 16 healthy control subjects. All patients were studied during an attack-free interval and during a migraine attack. Cerebrovascular reactivity was evaluated with the breath-holding index, obtained by dividing the percent increase in mean flow velocity occurring during breath-holding by the time (seconds) in which the subjects held their breath after a normal inspiration. The response to breath-holding was similar for all arteries considered in both control subjects and patients during the attack-free interval. During the migraine attack, the breath-holding index in patients was significantly lower than the migraine-free interval in all arteries (P < .001). No side-to-side difference in cerebrovascular reactivity was detected in migraine patients either outside or during attacks. These results suggest that a failure of cerebrovascular regulation occurs during attacks of migraine without aura.