Editor's Note: (This story was originally published on CNN.com in 2013.)
(CNN) About 37 million Americans suffer from migraines, those incredibly painful and often debilitating headaches. Though they've been known to knock a person out, migraines weren't thought to permanently affect the brain -- until now. A study published Wednesday in the journal Neurology suggests that migraines may indeed leave a mark.
"Our review and meta-analysis study suggests that the disorder may permanently alter brain structure in multiple ways," said study author Dr. Messoud Ashina, a neurologist at the University of Copenhagen in Denmark.
A migraine is a common type of headache in which throbbing pain is typically felt on just one side of the head. Sufferers experience sensitivity to light, nausea and vomiting. Women are three times more likely to be affected by migraines than men.
According to the American Migraine Foundation, migraines cost the United States more than $20 billion a year, both in direct medical expenses like doctor visits and medication and indirectly, when employees miss work resulting in lost productivity.
About 20% of migraine sufferers experience an aura, a warning symptom 20 minutes to an hour before a migraine begins. It's usually in the form of visual disturbances like wavy lines, dots or flashing lights, tingling in the face or arms, even difficulty speaking.
The study focused on three types of abnormalities that were detected by magnetic resonance imaging, or MRI. MRI tests use a magnetic field and radio wave energy to take pictures of organs inside the body. They can detect problems that often cannot be seen with an X-ray or ultrasound imaging.
Researchers reviewed six population-based studies and 13 clinic-based studies to see whether migraine sufferers had an increased risk of brain lesions, white matter abnormalities, infarct-like lesions or brain volume changes in both the gray and white matter regions of the brain. Infarct-like lesions, also called silent strokes, are changes neurologists usually see on MRI scans that look like minor strokes.
According to the study, the risk of white matter brain lesions increased 68% for those suffering migraines with aura, compared with non-migraine sufferers. Those who suffered from migraines without aura saw that increased risk cut in half (34%), but they too could get lesions in the part of the brain that is made up of nerve fibers.
Researchers found that white matter abnormalities are not limited to migraines; they also occur in non-migraine headaches. And people with migraines and migraines with aura were also more likely to have brain volume changes than those who don't suffer from migraines. But what these white matter abnormalities lead to is still unclear. That's why Ashina says more long-term studies are needed.
"Migraine affects about 10% to 15% of the general population and can cause a substantial personal, occupational and social burden," Ashina said. "We hope that through more study, we can clarify the association of brain structure changes to attack frequency and length of the disease. We also want to find out how these lesions may influence brain function."
Though migraines might be associated with structural changes in the brain, there's no cause for concern, Ashina determined.
"Studies of white matter changes showed no relationship to migraine frequency or cognitive status of patients."
Dr. MaryAnn Mays, a staff neurologist at the Center for Headache & Pain at the Cleveland Clinic, who was not involved in the research, agreed.
"What this study does demonstrate is yes, brain changes are more common in patients with migraines and probably are more common in patients with migraine aura," Mays said. "The good news is that ... long-term cognitive changes were not seen, even though these brain changes were apparent on imaging."
So do these brain changes pose a problem?
"I don't think, overall, in the long term, migraine sufferers need to be concerned," Mays said. "However, clinicians should screen for cardiovascular risk factors that may be apparent and can be modified -- such as hypertension and high cholesterol -- that could be contributing to white matter lesions that are unrelated to the migraine."
Mays is confident that headache experts are going to continue to monitor these changes to determine whether it will have any impact on the health of migraine sufferers.