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Shedding Light On Migraines

Boston researchers have seen the light on why light makes migraine headaches worse. The researchers believe that a new-found pathway is responsible for photophobia during episodes of migraine in both sighted and blind people. The scientists from Beth Deaconess Medical Center have published their results in the online journal called Nature Neuroscience.

Those who suffer from migraines often find the symptoms are aggravated by light and that staying in dark rooms, lessens migraine symptoms. Some migraine sufferers adopt the practice of wearing sunglasses, even at night. The fact that some blind people who experience migraines display the same sensitivity to light as the sighted intrigued researchers Rami Burstein, PhD, and Rodrigo Noseda, PhD.

Retinal Signals

Burstein, a professor of anesthesia and critical care at Beth Israel and Harvard Medical School, and Noseda hypothesized that the retina was sending signals to the optic nerve and that it was this transmission of signals that was responsible for triggering migraine headaches. The two scientists decided to study two groups of blind people who suffer from migraines. The patients in one group were completely blind due to eye disease, and were unable to see any images or sense light. Those in the second group were legally blind, and able to sense 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 explained. “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."

Transmission Process

Burstein and Noseda believed that a group of just-discovered retinal cells responsible for controlling functions such as sleep and wakefulness had a crucial role in this transmission process. Burstein notes that these cells are all that is left of a legally blind person's light receptors. In animal experiments, the researchers were able to trace the path of these cells from the optic nerve to the brain. As the cells traveled to the brain, a group of neurons showed electrical activity.

When researchers inserted tiny electrodes into these, "migraine neurons," they found that light triggered an electrical flow of signals straight to these same retinal cells. The activity in these cells increased within seconds. Even when the light was removed, the neurons remained active. Burstein thinks that this is the reason migraine sufferers find that light intensifies their headaches within seconds, but darkness only brings on improvement after 20 minutes to half an hour.

The implications of this study suggest that researchers may be able to find a way to block this pathway so that light won't worsen migraine pain.