[1] Univ Helsinki, Cent Hosp, Dept Neurol, FIN-00029 Helsinki, Finland
[2] Univ Bergen, Haukeland Hosp, Dept Neurol, N-5021 Bergen, Norway
[3] Kreiskrankenhauses, Siegen, Germany
[4] Univ Heidelberg, Dept Neurol, Heidelberg, Germany
[5] Lund Univ, Dept Radiol, Lund, Sweden
[6] Univ Edinburgh, Western Gen Hosp NHS Trust, Dept Clin Neurosci, Edinburgh, Midlothian, Scotland
[7] Karolinska Hosp, Dept Neurol, S-10401 Stockholm, Sweden