Why migraines strike.

For the more than 300 million people who suffer migraines, the excruciating, pulsating pain that characterizes these debilitating headaches needs no description. For those who do not, the closest analogous experience might be severe altitude sickness: nausea, acute sensitivity to light, and searing, bedconfining headache. “That no one dies of migraine seems, to someone deep into an attack, an ambiguous blessing,” wrote Joan Didion in the 1979 essay “In Bed” from her collection The White Album.