We're all swept from time to time by the occasional migraine, and rest assured you don't want anyone around you when that time comes. Some people, however, suffer from migraines more often than others in what's recently been classified as chronic migraines. It's still unclear what causes them. Some studies point to dilation of blood vessels in the head, it's even been attributed to abnormal neuronal signals, while most recently researchers in the Perelman School of Medicine at the University of Pennsylvania report that the network of arteries supplying blood flow to the brain is more likely to be incomplete in people who suffer migraine.
"People with migraine actually have differences in the structure of their blood vessels - this is something you are born with," said the study's lead author, Brett Cucchiara, MD, Associate Professor of Neurology. "These differences seem to be associated with changes in blood flow in the brain, and it’s possible that these changes may trigger migraine, which may explain why some people, for instance, notice that dehydration triggers their headaches."
The arterial supply of blood to the brain is protected by a series of connections between the major arteries, termed the "circle of Willis" after the English physician who first described it in the 17th century. People with migraine, particularly migraine with aura - a migraine that's preceded or accompanied by sensory warning signs or symptoms, such as flashes of light, blind spots, or tingling in your hand or face - are more likely to be missing components of the circle of Willis, according ot University of Pennsylvania researchers.
In a study of 170 people from three groups - a control group with no headaches, those who had migraine with aura, and those who had migraine without aura - the team found that an incomplete circle of Willis was more common in people with migraine with aura (73 percent) and migraine without aura (67 percent), compared to a headache-free control group (51 percent). The team used magnetic resonance angiography to examine blood vessel structure and a noninvasive magnetic resonance imaging method pioneered at the University of Pennsylvania, called Arterial spin labeling (ASL), to measure changes in cerebral blood flow.
"Abnormalities in both the circle of Willis and blood flow were most prominent in the back of the brain, where the visual cortex is located. This may help explain why the most common migraine auras consist of visual symptoms such as seeing distortions, spots, or wavy lines,” said the study’s senior author, John Detre, MD, Professor of Neurology and Radiology.
Migraine affects an estimated 28 million Americans, causing significant disability in day to day activities. Both migraine and incomplete circle of Willis are common, and the observed association is likely one of many factors that contribute to migraine in any individual.