[1] Sorlandet Hosp, Dept Neurol, Kristiansand, Norway
[2] Univ Hosp, Hosp Rehabil, Rikshosp, Kristiansand, Norway
[3] Nordland Hosp, Dept Neurol, Bodo, Norway
[4] Univ Tromso, Inst Neurol, Tromso, Norway
[5] Univ Bergen, Inst Clin Med, Bergen, Norway