Sunday, January 10, 2010

New Light on Migraines

Main points from a Science Daily post:
  • Migraine pain is believed to develop when the meninges (the system of membranes surrounding the brain and central nervous system) becomes irritated.
  • For unknown reasons, nearly 85 percent of migraine patients are also extremely sensitive to light, a condition known as photophobia.
  • Two groups of blind individuals who suffer migraine headaches, were studied. 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.
  • This suggested to researchers 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."
  • 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."
Related update (Jan 14, 2010): "Migraine and depression may share genetic component."