Researchers believe they know why light exacerbates the already debilitating pain of migraines, even in some blind people.

A report published in Nature Neuroscience reveals how visual and pain pathways in the brain converge to produce this phenomenon.

The Boston-based researchers report there are cells in a part of the brain called the thalamus “where information from the visual system and information from the pain system converge, and that anatomic convergence provides the first available explanation for how it could be that light makes pain worse,” said Dr. Richard Lipton, director of the Montefiore Headache Center and professor of neurology and epidemiology at Albert Einstein College of Medicine in New York City.

According to the study, about 85 percent to 90 percent of all migraine sufferers report having photophobia, which is when light makes the pain worse.

To solve the paradox, the team studied 20 blind individuals, all of whom suffered from migraines. Six participants had no light perception at all and no functioning optic nerve. These individuals also experienced no photophobia.

The remaining 14 people could sense light and dark and also experienced photophobia.

The study showed that the optic nerve is critically needed in order to produce photophobia or exacerbation of the headache by light.

Senior author Rami Burnstein, a professor of anesthesia and neuroscience at Harvard University, said the study “identified a new pathway in the brain that originates in the eye and goes to the brain areas where neurons are found that are active during migraine attacks. The light can increase the electrical activity in neurons that are active to begin with.”

The findings should put to rest any thoughts that patients exaggerate their sensitivity to light, Lipton said. “This provides an anatomic and physiological basis for a common experience — that light makes pain worse, not because you’re a whiner, but because there is an anatomic pathway that links the visual system to the pathway that produces head pain.”

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