Flashes of light, visual disturbances - one-of-five people who get migraines have these auras that warn them they're about to have an attack.
Now, researchers have been able, with the help of functional magnetic resonance imaging (fMRI), to capture the aura from beginning to end, and observe the brain activity taking place just before the migraine strikes.
"We were very lucky to find a subject who could trigger the aura," says Dr Nouchine Hadjikhani, study co-author and an instructor in radiology at Harvard Medical School and Massachusetts General Hospital.
A man who said playing basketball triggered flashes of light, which were often accompanied by loss of vision, was told to play to his heart's content, then rush to the hospital when he felt an attack coming on.
The researchers would have him jump into the scanner and follow the progressions, says Hadjikhani. "What we saw was there was a change in the signal that correlated with [the] visual perception of the subject."
"The bold changes we were observing showed us there are more chances it [the aura] was a neuronal event," rather than having to do with something happening in the blood vessels, says Hadjikhani. And, researchers add, the ability to capture images of the auras "substantiate the organic nature of migraine and chronic daily headache and that they are real."
The fMRI recorded events in the occipital cortex, the area of the brain in the back of the head that controls vision. Researchers found that at the beginning of the aura, the neurons were firing at the back of the visual cortex and spreading forward, akin to waves in a pond after a pebble has been tossed in the water.
Typically, the visual images of an aura last about 15 minutes, researchers say, and pain medication taken while the aura's in progress doesn't work.
"This finding may facilitate treatment of migraine before the headache itself manifests," says Dr Seymour Diamond, director and founder of the National Headache Foundation. And, "the earlier you treat a migraine attack, the more successful you will be in reversing the symptoms."
For many of the 30 million Americans who have migraines, Hadjikhani adds, "if we could abort it beforehand... it would be like getting on the train one station earlier."
The results of the study were presented recently at the 10th International Headache Congress of the International Headache Society.
What to do
Whether or not your migraines are preceded by auras, you should seek medical help to control the pain and attacks. Since many things trigger migraine pain, keep track of the things you eat, what you're doing and your moods to help you and your doctor track the causes.