A recent study by researchers from the Perelman School of Medicine at the University of Pennsylvania has shown the arteries supplying blood flow to the brain is more likely to be incomplete in people who experience migraine. The arterial supply of blood to the brain is protected by numerous connections between the major arteries which is known as the circle of Willis. Those who experience migraine and especially migraine with aura are more likely than those without migraine to be missing some components of the circle of Willis. These structural changes in the circle of Willis are something people are born with.
In this study, which appeared in PLOS ONE, the researchers suggest that these structural alterations of the blood supply to the brain may increase susceptibility to changes in cerebral blood flow, which may contribute to abnormal neuronal activity that starts migraine. Experts used to believe that migraine was caused by dilation of blood vessels but now believe it is caused by abnormal neuronal signals.
In the study, the researchers used 170 people consisting of a control group with no headaches, a group of those who have migraine with aura, and a group of those who have migraine without aura. The researchers found an incomplete circle of Willis was more common in those with migraine with aura (73%) and migraine without aura (67%) when compared to those who are headache free (51%). The researchers used magnetic resonance angiography to examine blood vessel structure and magnetic resonance imaging with arterial spin labeling (ASL) to measure changes in cerebral blood flow.
The researchers also found that the most prominent abnormalities were found in the back of the brain where the visual cortex is located which may explain why those with migraine with aura experience numerous visual symptoms. The researchers feel that eventually it may be possible to run diagnostic tests of the circle of Willis in those with migraine to help better development treatment strategies.
Reference: Brett Cucchiara, and et. al., “Migraine with Aura Is Associated with an Incomplete Circle of Willis: Results of a Prospective Observational Study,” PLoS ONE, 2013; 8 (7): e71007