[1] Brigham & Womens Hosp, Harvard Med Sch, Dept Anesthesiol Perioperat & Pain Med, Boston, MA USA
[2] Beth Israel Deaconess Med Ctr, Harvard Med Sch, Dept Anesthesia Crit Care & Pain Med, Boston, MA USA
[3] Copenhagen Univ Hosp, Rigshospitalet, Danish Headache Ctr, Dept Neurol, Copenhagen, Denmark
[4] Univ Copenhagen, Fac Hlth & Med Sci, Dept Clin Med, Copenhagen, Denmark
[5] Copenhagen Univ Hosp, Rigshospitalet, Dept Brain & Spinal Cord Injury, Copenhagen, Denmark
[6] Beth Israel Deaconess Med Ctr, Harvard Med Sch, Dept Neurol, Boston, MA USA
[7] Albert Einstein Coll Med, Montefiore Headache Ctr, Dept Neurol, Bronx, NY USA
[8] Beth Israel Deaconess Med Ctr, BIDMC Comprehens Headache Ctr, Boston, MA USA