 For a billion people worldwide, the symptoms can be debilitating, throbbing, head pain, nausea, blurred vision, fatigue that can last for days. But how the brain activity triggers the severest of headaches, migraines, has long puzzled scientists. No, not at all. There's no puzzle at all. It's simply the result. There's a complexity to it, but simply the result of the way the head is sitting on top of the neck.