WEDNESDAY, Oct. 3, 2001 (HealthDayNews) -- The auras that foreshadow migraines for some people might be more than a harbinger of pain. New research shows they may actually trigger the intense throbbing associated with this kind of headache.
Using laboratory rats, scientists from Harvard University found a direct link between the aura, a visual disturbance generated in the brain, and the actual pain of a migraine. The discovery could eventually lead to better treatments for this type of migraine, researchers say. Approximately 30 million Americans, mostly women, have migraines every year, and one in five sufferers has migraines that start with auras.
"This is the first time we are proving this missing link," says Dr. Hayrunnisa Bolay, lead author of the study. "We think these auras might be one of the triggers. If we can understand these mechanisms, now we can say there's an activation point in migraines."
Bolay presented her findings Oct. 1 at the annual meeting of the American Neurological Association in Chicago.
In the study, researchers started with the premise that auras are tied to a brain phenomenon called cortical spreading depression (CSD). The pain of migraines has been traced to inflammation and blood flow changes in the dura mater, a membrane that covers the brain. And scientists have long suspected that CSD somehow stimulates the trigeminal nerve pain system, from which all head pain comes.
In the latest study, researchers induced CSD in rats and then measured blood flow in their dura mater, using a novel imaging technique they developed called "speckle imaging." This gives researchers a highly magnified view of what is happening in real time in the brain's blood vessels.
They found one wave of CSD increased blood flow in the dura mater for 45 minutes. The trigeminal nerve was clearly responsible for this increased blood flow because when researchers cut the nerve, CSD no longer led to increased blood flow in the dura mater.
One migraine expert says the study breaks new ground.
"This is the first study that has shown CSD does induce the changes in blood vessels that we suspect occurs in migraines. I think it's interesting and it's important," says Dr. Fred Sheftell, president of the American Council for Headache Education (ACHE). "Studies like this really help us to demonstrate the validity of migraines as a neurobiological disorder."
He also has praise for the "speckle imaging" technique: "I think it's important new technology. There's more to learn about how to apply this to humans."
Other researchers at Harvard have already captured the spread of an aura in a human with functional magnetic resonance imaging (fMRI).
The fMRI recorded events in the occipital cortex, the area of the brain in the back of the head that controls vision. Researchers found the neurons first fired at the back of the visual cortex and spread forward.
Sheftell says the most recent findings still have to be shown in humans.
But Bolay notes that "speckle imaging" is an invasive technique, so it can only be used on animals, although it could be a useful way to track the effects of new drugs designed to ease migraines. The process involves removing part of the skull and then lighting the brain with a laser. The scattered light hits a camera, which records blood flow images in real time.
"If we understand how the brain kick-starts pain, we would be able to develop better drugs," she says. "Now we understand why we have head pain. If we could understand what triggers it, we could block the headache."
What To Do
Get more information about migraine headaches from the National Migraine Association or the National Headache Foundation.
Visit ACHE for more on women and migraines.
Learn the language of headache with the migraine glossary.
Curious about how "speckle imaging" works? Here's an explanation from Optics.org.
