You are suddenly hit with a severe headache that you’ve never experienced before. Maybe you pass out; maybe it makes you sick to your stomach. Should you go to the ER? Emergency physician Dr. Troy Madsen says these “thunderclap headaches” might be a sign of something much more serious. On this episode of "ER or Not" we talk what potentially life threatening problems that a severe headache might be a sign of, and how to distinguish them from a normal headache.