[1] Univ Copenhagen, Rigshosp Glostrup, Fac Hlth & Med Sci, Dept Neurol,Danish Headache Ctr, Valdemar Hansen Vej 5, DK-2600 Glostrup, Denmark
[2] Rigshosp, Dept Neurorehabil & Traumat Brain Injury, Copenhagen, Denmark
[3] Harvard Med Sch, Beth Israel Deaconess Med Ctr, Comprehens Headache Ctr, Boston, MA 02115 USA
[4] Harvard Med Sch, Beth Israel Deaconess Med Ctr, Dept Neurol, Boston, MA 02115 USA
[5] Harvard Med Sch, Beth Israel Deaconess Med Ctr, Dept Anesthesia Crit Care & Pain Med, Boston, MA 02115 USA
[6] Univ Copenhagen, Fac Hlth & Med Sci, Dept Clin Med, Copenhagen, Denmark
[7] Albert Einstein Coll Med, Dept Neurol, Bronx, NY 10467 USA
[8] Montefiore Headache Ctr, Bronx, NY USA