People who experience migraines are more likely to have gaps in the network of arteries that pumps blood throughout the brain, according to a new study published yesterday in the journal PLOS One. The resulting imbalance in cerebral blood flow could be a factor in triggering the debilitating headaches, the researchers said.
Migraines, which can be excruciating and sometimes last for up to 72 hours, affect an estimated 28 million people in the U.S. In 1965, researchers first suggested that susceptibility to migraines was related to the structure of the circle of Willis – the loop of arteries that directs blood flow through the brain. The exact cause of migraines is still unknown, and more recent scholarship has pointed to a variety of contributing factors – including overactive neuron signaling and environmental cues – but the current study adds to the evidence that the circle of Willis plays a critical role in migraine development.
Researchers from the University of Pennsylvania examined the arteries and blood flow in the brains of 170 25-50 year old individuals using magnetic resonance imaging techniques. One group of subjects suffered from migraines, a second group experienced migraines with aura – symptoms like seeing spots and wavy lines that begin about half an hour before the migraine sets in — and the final, control group did not suffer from migraines.
Compared to the control group, people who experienced migraines with aura were significantly more likely to have an incomplete circle of Willis — 73 percent of those with migraine with aura versus 51 percent of the control. While there was a trend for incomplete circle of Willis in people with migraine alone – 67 percent – the result was not statistically significant.
In addition, people who had incomplete circles of Willis had greater asymmetry in the blood flow throughout the brain compared to people with complete arterial circles. The blood flow was most disrupted in the back of the brain for these subjects, which is where visual processing occurs. This phenomenon might help explain the visual hallucinations associated with aura, noted the study’s lead author.
An incomplete circle of Willis is likely one of many risk factors for migraine, which has in turn been linked to increased risk for stroke. The researchers hope that their findings will help doctors categorize migraine patients based on their individual headache components, potentially aiding in the selection of treatment strategies.