Abnormal Cerebrovascular Reactivity in Headache-Free Migraineurs

The thermographic finding of a unilateral 'cold patch' on the forehead of both classic and common migraine sufferers has prompted the suggestion that there is an asymmetry in the vasomotor tone of superficial extracranial arteries that could also be present in cerebral vessels. Transcranial Doppler sonography allows the study of the response of intracranial arteries to variations of blood PCO2, which may give an estimate of vasomotor tone regulation. Thirty headache-free migraineurs were compared to 30 age-matched controls. The provocative test consisted of a 30-second apnea, followed by hyperventilation for 1 min. End-tidal pCO2 was assessed by means of a capnometer. The mean flow velocity of the middle cerebral artery was monitored throughout the testing session by means of a 2-MHz transcranial Doppler probe. Baseline mean flow velocities were not statistically different between right and left sides in both controls and migraineurs and between ipsilateral (to the 'cold patch') and contralateral side in migraineurs. During apnea migraineurs, ipsilaterally to the 'cold patch', showed a significantly lower increment in mean flow velocity than controls. Following apnea and during maximal hyperventilation, migraineurs showed a bilateral vasoconstriction significantly more pronounced than controls. End-tidal pCO2 was not statistically different between migraineurs and controls. The findings suggest that the cerebral arterioles of migraineurs are more likely to undergo vasoconstriction when PCO2 is reduced. In addition, there seems to be a unilaterally more pronounced tendency to resist a vasodilatory stimulation.