[1] Univ Copenhagen, Herlev Hosp, Childrens Headache Clin, Dept Paediat, DK-2730 Copenhagen, Denmark
[2] Univ Copenhagen, Herlev Hosp, Med Dept O, Dept Physiotherapy, DK-2730 Copenhagen, Denmark
[3] Rigshosp, Copenhagen Univ Hosp, Dept Neuropediat, DK-2100 Copenhagen, Denmark
[4] Univ Copenhagen, Dept Biostat, Copenhagen, Denmark