London, Jan 11 (ANI): For those who suffer from migraine, slipping on a pair of sunglasses may help ease the chronic pain, say researchers.
Although it's long been known that light makes migraines worse, the reason why has been unclear.
A research team from Beth Israel Deaconess Medical Centre have explained why light makes migraines worse.
They have identified a new visual pathway that underlies sensitivity to light during migraine in both blind individuals and in individuals with normal eyesight.
Migraine pain is believed to develop when the meninges, the system of membranes surrounding the brain and central nervous system, becomes irritated, and nearly 85 percent of migraine patients are become extremely sensitive to light, a condition known as photophobia.
"Migraine patients may wear sunglasses, even at night," Nature Neuroscience quoted study's senior author Dr Rami Burstein, Professor of Anesthesia and Critical Care Medicine at BIDMC and Harvard Medical School, as saying.
He added that the dimmest of light could make migraine pain worse.
It was the observation that even blind individuals who suffer from migraines were experiencing photophobia that led Burstein and first author Rodrigo Noseda, PhD, to hypothesize that signals transmitted from the retina via the optic nerve were somehow triggering the intensification of pain.
The investigators studied two groups of blind individuals who suffer migraine headaches. Patients in the first group were totally blind due to eye diseases such as retinal cancer and glaucoma; they were unable to see images or to sense light and therefore could not maintain normal sleep-wake cycles.
Patients in the second group were legally blind due to retinal degenerative diseases such as retinitis pigmentosa.
While they were unable to perceive images, they could detect the presence of light and maintain normal sleep-wake cycles.
"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 said.
"This suggested to us that the mechanism of photophobia must involve the optic nerve, because in totally blind individuals, the optic nerve does not carry light signals to the brain," he added.
During the study, researchers performed a series of experiments in an animal model of migraine. After injecting dyes into the eye, they traced the path of the melanopsin retinal cells through the optic nerve to the brain, where they found a group of neurons that become electrically active during migraine.
"When small electrodes were inserted into these 'migraine neurons,' we discovered that light was triggering a flow of electrical signals that was converging on these very cells," said Burstein. "This increased their activity within seconds."
And even when the light was removed, he notes, these neurons remained activated.
"This helps explain why patients say that their headache intensifies within seconds after exposure to light, and improves 20 to 30 minutes after being in the dark," he added. (ANI)