“This explains the throbbing headache and accompanying scalp and neck-muscletenderness experienced by many migraine patients,” said the study’s seniorauthor, Rami Burstein, a Harvard Medical School professor of anesthesia and critical care medicine atBIDMC.In addition, for reasons that have been unknown, nearly 85 percent of migrainepatients are also extremely sensitive to light, a condition known asphotophobia.“Migraine patients may wear sunglasses, even at night,” he said, adding thatthe dimmest of light can make migraine pain worse. Extremely disabling,photophobia can prevent patients from such routine activities as reading,writing, working, or driving.It was the observation that even blind individuals who suffer from migraineswere experiencing photophobia that led Burstein and first author Rodrigo Nosedato hypothesize that signals transmitted from the retina via the optic nervewere somehow triggering the intensification of pain.The investigators studied two groups of blind individuals who suffer migraines.Patients in the first group were totally blind due to eye diseases such asretinal cancer and glaucoma; they were unable to see images or to sense light,and therefore could not maintain normal sleep-wake cycles. Patients in thesecond group were legally blind due to retinal degenerative diseases such asretinitis pigmentosa; although they were unable to perceive images, they coulddetect the presence of light and maintain normal sleep-wake cycles.“While the patients in the first group did not experience any worsening oftheir headaches from light exposure, the patients in the second group clearlydescribed intensified pain when they were exposed to light, in particular blueor gray wavelengths,” said Burstein. “This suggested to us that the mechanismof photophobia must involve the optic nerve, because in totally blindindividuals, the optic nerve does not carry light signals to the brain.“We also suspected that a group of recently discovered retinal cells containingmelanopsin photoreceptors [which help control biological functions includingsleep and wakefulness] is critically involved in this process, because theseare the only functioning light receptors among patients who are legally blind.”The scientists took these ideas to the laboratory, where they performed aseries of experiments in “an animal model” of migraine. After injecting dyesinto the eye, they traced the path of the melanopsin retinal cells through theoptic nerve to the brain, where they found a group of neurons that becomeelectrically active during migraine.“When small electrodes were inserted into these ‘migraine neurons,’ wediscovered that light was triggering a flow of electrical signals that wasconverging on these very cells,” said Burstein. “This increased their activitywithin seconds.”And even when the light was removed, he said, these neurons remained activated.“This helps explain why patients say that their headache intensifies withinseconds after exposure to light, and improves 20 to 30 minutes after being inthe dark.” Thediscovery ofthis pathway provides scientists with a new avenue to follow in working toaddress the problem of photophobia.“Clinically, this research sets the stage for identifying ways to block thepathway so that migraine patients can endure light without pain,” saidBurstein.In addition to Noseda and Burstein, co-authors include BIDMC investigatorsVanessa Kainz, Moshe Jakubowski, Joshua Gooley, and Clifford B. Saper, alongwith Kathleen Digre of the University of Utah. The study was funded by grantsfrom the National Institutes of Health and from Research to Prevent Blindness. Normal0017014001338491311.1282000Askpeople who suffer from migraine headaches what they do when they’re having attacks,and you’re likely to hear “go into a dark room.” Although it’s long been knownthat light makes migraines worse, the reason why has been unclear. NowHarvard scientists at Beth Israel Deaconess Medical Center (BIDMC) have identified a visualpathway that underlies sensitivity to light during migraines. Thefindings, which were published in yesterday’s advance online issue of NatureNeuroscience, help to explain the mechanism behind this widespread condition.The research involved blind individuals and those with normal eyesight. Amigraine is a one-sided, throbbing headache associated with a number ofsymptoms, including nausea, vomiting, and fatigue. Migraines are notoriouslydebilitating and surprisingly widespread, affecting more than 30 million peoplein the United States alone. Migraine pain is believed to develop when themeninges, the system of membranes surrounding the brain and central nervoussystem, become irritated, which stimulates pain receptors and triggers a seriesof events that lead to the prolonged activation of groups of sensory neurons.