Affecting 28 millions of Americans, migraines can be debilitating enough to prevent people from working, spending time with their families, and can lead to depression. This form of headache can last from hours to weeks and are a major problem for close to 10 percent of the country. While migraines were once thought to be caused by the dilation of blood vessels, researchers using new technologies to look at the brain in high resolution are discovering that certain arterial formations are missing in patients who suffer from migraine pain.

New research from the University of Pennsylvania and published today in the journal PLoS One explores a specific type of blood vessel abnormality seen in patients who suffer from migraines. Researchers have observed that the blood flow in the brain, which flows through a circular structure, abruptly ends. The circle of Willis, a major circle of arteries through which the entire blood supply passes, appeared to be missing components when examined.

Researchers have recently pointed at abnormal neural signals in the brain and propose that the altered blood flow in migraine patients may contribute to the abnormal brain activity.

"People with migraine actually have differences in the structure of their blood vessels — this is something you are born with," said the study lead author, Dr. Brett Cucchiara, 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 study examined 170 people split into three groups, those with no headaches, those who had migraine with aura, and those who had migraine without aura. An aura is a perceptual disturbance that migraine sufferers experience before a headache. They found that the group who had migraines with aura commonly had an incomplete circle of Willis. The abnormality was seen at a rate of 73 percent in those who had migraine with aura, 67 percent of those who had migraine without aura, and in 51 percent of those without migraines.

"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, Dr. John Detre, professor of neurology and radiology.

Source: Wolf R, Nagae L, Zhang Q, etal. Migraine with Aura Is Associated with an Incomplete Circle of Willis: Results of a Prospective Observational Study. PLoS One. 2013.