Why Light Worsens Migraine Headaches
Blind Patients Help Scientists Understand the Link Between Light and Headaches
Jan. 12, 2010 -- Researchers in Boston say they’ve gained new insight into why light makes migraine headaches so painful.
The culprit, they say, is a new pathway that underlies sensitivity to light during migraine episodes in blind people and people with normal eyesight. Scientists at Beth Deaconess Medical Center report their findings in the online journal Nature Neuroscience.
Migraines, which afflict more than 30 million people in the United States, are painful headaches for which sufferers often seek relief by going into dark rooms. Migraines are believed to develop when the system of membranes surrounding the brain and central nervous system, called the meninges, becomes irritated.
That stimulates pain receptors and triggers a series of events that lead to prolonged activation of groups of sensory neurons, the scientists report.
“This explains the throbbing headache and accompanying scalp and neck-muscle tenderness experienced by many migraine patients,” says Rami Burstein, PhD, professor of anesthesia and critical care at Beth Israel and Harvard Medical School.
Migraines cause one-sided, throbbing pain, and have been called “sick headaches” because they have long been associated with vomiting, nausea, irritability, and fatigue.
People with migraines also are also typically aggravated by light with worsening of symptoms compared to being in the dark. This causes many migraine sufferers to wear sunglasses, often at night, Burstein says.
It was the observation that even blind people who suffer migraines were experiencing sensitivity to light, referred to as photophobia, that led Burstein and Rodrigo Noseda, PhD, to hypothesize that signals transmitted from the retina to the optic nerve were triggering the intense headaches, the authors say.
The scientists studied two groups of blind people with migraines. Patients in one group were totally blind because of eye diseases, unable to see images or sense light.
People in a second group were legally blind, but were able to detect the presence of light.
“While the patients in the first group did not experience any worsening of their headaches from light exposure, the patients in the second group clearly described intensified pain when they were exposed to light, in particular blue or gray wavelengths,” Burstein says in a news release. “This suggested to us that the mechanisms of photophobia must involve the optic nerve, because in totally blind individuals, the optic nerve does not carry light signals to the brain.”