If you’ve ever had a migraine headache, you don’t need me to tell you it hurts. Doctors report that about twenty million people suffer from serious headaches, and ten percent of these have intractable pain–meaning it doesn’t go away. But here’s a surprise: the problem isn’t always a migraine. Sometimes very similar symptoms are caused by damage to a nerve of the face, which results in the nerve itself sending nonstop “ouch” signals.