One of the most common symptoms of Migraine is photophobia – increased, often painful sensitivity to light.
Photophobia can begin as early as the prodrome phase of a Migraine attack and continue through the headache phase.
Many people with Migraine also experience photophobia interictally (between Migraine attacks.) Another problem with photophobia is that it often makes Migraine pain worse.
Until fairly recently, why light worsened Migraine pain was a mystery, but a 2010 study1 by Burstein et. al. showed that visual and pain pathways converge in the brain, causing light to worsen the pain of a Migraine.
During an interview, Dr. Burstein commented:
“We had no clue in the world where in the world light and pain talk to each other in the brain. They have completely different pathways in the brain… We identified a new pathway in the brain that originates in the eye and goes to the brain areas where neurons are found that are active during migraine attacks. The light can increase the electrical activity in neurons that are active to begin with.”4
Other comments from Burstein explained their findings:
“This explains the throbbing headache and accompanying scalp and neck-muscle tenderness experienced by many migraine patients.
Migraine patients may wear sunglasses, even at night… the dimmest of light can make migraine pain worse. Extremely disabling, photophobia prevents patients from such routine activities as reading, writing, working or driving.
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. 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.
We also suspected that a group of recently discovered retinal cells containing melanopsin photoreceptors [which help control biological functions including sleep and wakefulness] is critically involved in this process, because these are the only functioning light receptors left among patients who are legally blind.
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…
(regarding the neurons remaining activated when light was removed) 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.
Clinically, this research sets the stage for identifying ways to block the pathway so that migraine patients can endure light without pain.”2
Especially given how much about how Migraine really works in our brains is still not understood, this is exciting research. Now that the pathway responsible for light making Migraine pain worse has been identified, researchers can work to identify ways to block the effects of light on Migraine. Another real possibility is that this discovery may well lead to better understanding of our sensitivities to sound and smell.
When the findings of this study were released, I wanted to get the opinion of another Migraine researcher to be sure that my impression wasn’t colored by wishful thinking. I contacted Dr. Richard Lipton and will share some of his comments with you. He summarized this research and it’s importance and implications far more succinctly than I can:
“This research began with an intriguing question about photophobia; ‘How is that light worsens pain during a migraine attack?’ By evaluating patients who are blind, Burstein and coworkers discovered that in some forms of blindness, migraine pain is worsened by light even in people who can not see. In these patients, a specific population of cells (called RGC or retinal ganglion cells) in the retina are preserved while other cells, responsible for formed vision (rods and cones) are lost. Building on this clinical observation, Burstein discovered a place deep in the brain where input from these RGCs about light conditions and input from the pain pathway converge. Light worsens pain by activating nerve cells at this point of convergence.
These finding are important because:
- They make clear that light sensitivity in migraine has a firm anatomic basis. The symptom can be understood.
- They help us understand why drugs that relieve the pain of migraine also relieve sensitivity to light.
- They may provide a model for helping us understand sound and smell sensitivity as well.”3