[1] Umea Univ, Dept Pharmacol & Clin Neurosci, S-90187 Umea, Sweden
[2] Univ Helsinki, Cent Hosp, Dept Neurol, FIN-00014 Helsinki, Finland
[3] Glostrup Cty Hosp, Dept Neurol, Danish Headache Ctr, Glostrup, Denmark
[4] Univ Copenhagen, DK-1168 Copenhagen, Denmark
[5] Univ Trondheim Hosp, Norwegian Natl Headache Ctr, Trondheim, Norway
[6] Norwegian Univ Sci & Technol, Dept Neurosci, Trondheim, Norway
[7] Ostersund Hosp, Unit Res Educ & Dev, Ostersund, Region Jamtland, Sweden
[8] Univ Trondheim Hosp, Dept Neurol, Trondheim, Norway
[9] Folkhalsan Res Ctr, Inst Genet, Helsinki, Finland
[10] Univ Helsinki, Inst Mol Med Finland FIMM, FIN-00014 Helsinki, Finland
[11] Oslo Univ Hosp, Dept Neurol, N-0450 Oslo, Norway
[12] Oslo Univ Hosp, FORMI, N-0450 Oslo, Norway
[13] Univ Oslo, N-0316 Oslo, Norway