Researchers say a finding that links light and migraine headache pain probably won't lead to new treatments for migraine pain itself, but could help scientists find a drug to ease the sensitivity to light.
Researchers say a finding that links light and migraine headache pain probably won't lead to new treatments for migraine pain itself, but could help scientists find a drug to ease the sensitivity to light. iStockphoto.com
A study of blind people has revealed how bright light can intensify the pain of a migraine headache.
The study, published in Nature Neuroscience, found a pathway between light-sensitive cells in the retina and an area in the brain that's involved in migraine pain. The retinal cells don't contribute to vision, so they are still functioning in the eyes of many blind people whose other retinal cells no longer work.
"Why it should be that light makes pain worse during migraine had remained a mystery until this study," says Richard B. Lipton, who directs the Montefiore Headache Center at the Albert Einstein College of Medicine in New York. He was not involved in the research.
The finding could help scientists explain why some migraine sufferers are also sensitive to certain smells and sounds, Lipton says.
The study involved 20 migraine sufferers who had little or no vision.
It showed that people who had lost their eyes or suffered damage to the ocular nerve were not affected by exposure to bright light, says Rami Burstein, an author of the study and a migraine researcher at Beth Israel Deaconess Medical Center in Boston.
But light did increase migraine pain in people who still had functioning photoreceptors called retinal ganglion cells, Burstein says.
One of those people was Heather Bird, 22, of Rochester, N.Y., who volunteered to participate in the study.
Bird says a genetic disorder has left her blind and unable to tell if the world is bright or dim most of the time. But if she has a migraine and feels a "stab of pain" the moment she steps outside, she knows the sun must be out.
Burstein says the results with blind people helped his team design a series of studies in rats to track the signals from retinal ganglion cells. The studies showed that the signals go to "brain areas that have nothing to do with visual perception."
Some of these areas probably help the brain maintain circadian rhythms, Burstein says. But others are involved in pain, including migraine pain.
That would explain how light could intensify the pain of a migraine even in someone who is blind, he says.
Burstein says the finding probably won't lead to new treatments for migraine pain itself. But it could help scientists find a drug that would let migraine patients leave the confines of a dark room without feeling more pain.