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Approximately 30 million people in the United States suffer from migraine pain, which is often described as a throbbing pain in one area of the head and is often accompanied by nausea, vomiting and other symptoms.

In addition, for reasons unknown, approximately 85 percent of migraine patients are also extremely sensitive to light, which a condition that is called photophobia. Thus, this condition explains why most migraine sufferers finds benefit retreating to a dark environment when such attack happens.

Rami Burstein, professor of critical care medicine and anesthesia at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston, Massachusetts is researching on identifying ways to block the pathway so that migraine patients can endure light without pain

Even the blind patients that suffered from migraines showed photophobia. So, the researchers hypothesized that the signals that are transmitted from the retina along the optic nerve were somehow triggering the intensification of the pain.

In the research, scientists examined two groups of blind patients who suffered from migraine headaches. The first group of patients was totally blind and was unable to sense light or see images. The second group of patients was considered legally blind due to retinal degenerative diseases that could not perceive images but they could detect light. The first group, who couldn't sense light, showed no worsening of their headaches when they were exposed to light. Those that were in the second group described an increase in their pain when exposed to light.

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.

 The scientists then tested out this theory in a lab by injecting dyes into the eyes of rats that had migraine headaches. By following the dyes, the researchers traced the path of the melanopsin retinal cells through the optic nerve to the brain, where they found a group of brain cells that became electrically active when suffering from a migraine.

Burstein stated, 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. This increased their activity within seconds.

Even when the light was removed, Burstein said that the neurons still 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.

The results of this study are detailed online in the journal Nature Neuroscience.