[1] Univ Copenhagen, Fac Hlth & Med Sci, Danish Headache Ctr, Dept Neurol,Rigshosp Glostrup, Copenhagen, Denmark
[2] Natl & Kapodistrian Univ Athens, Aeginit Hosp, Neurol Dept 1, Athens, Greece
[3] Teva Branded Pharmaceut Prod R&D Inc, W Chester, PA USA
[4] Univ Duisburg Essen, Inst Med Informat Biometry & Epidemiol, Med Fac, Essen, Germany
[5] Univ Copenhagen, Fac Med & Hlth Sci, Danish Headache Ctr, Dept Neurol,Rigshosp Glostrup, Valdemar Hansens Vej 5, DK-2600 Glostrup, Denmark