[1] Sorlandet Hosp, Dept Neurol, N-4604 Kristiansand, Norway
[2] Univ Hosp, Rikshosp, Hosp Rehabil, Kristiansand, Norway
[3] Univ Bergen, Inst Clin Med, Bergen, Norway
[4] Nordland Hosp, Dept Neurol, Bodo, Norway
[5] Univ Tromso, Dept Neurol, Tromso, Norway