Cerebral blood flow velocities are reduced during attacks of unilateral migraine without aura.

It has been disputed whether or not large intracranial arteries are dilated during migraine attacks. In order to answer this question the present transcranial Doppler study focused on side-to-side differences of middle cerebral artery blood velocity during unilateral attacks of migraine without aura in 25 patients. Blood velocity in the middle cerebral artery was lower on the headache side (59 cm/s) than on the non-headache side (65 cm/s) during the migraine attack. No such difference was found outside of attack (65 cm/s both sides). The difference (headache side minus non-headache side) was on average -6.1 cm/s during attack compared to -0.4 cm/s outside of attack (p = 0.01). Assuming that rCBF is unchanged during attacks of migraine without aura, our results suggest a 9% increase in middle cerebral artery lumen (cross-sectional area) on the affected side during unilateral attacks of migraine without aura. The findings, however, do not necessarily mean that arterial dilatation is the only or even the most significant cause of pain.