[1] Oslo Univ Hosp, Dept Neurol, POB 4956 Nydalen, N-0424 Oslo, Norway
[2] Oslo Univ Hosp, Dept Hematol, Oslo, Norway
[3] Telemark Hosp Trust, Med Genet Sect, Dept Lab Med, Skien, Norway
[4] St Olavs Hosp, Dept Neurol, Trondheim, Norway
[5] NTNU, Dept Neurosci, Trondheim, Norway
[6] NeuroClinic, Dept Neurol, Lillestrom, Norway
[7] Univ Gothenburg, Sahlgrenska Acad, Dept Neurol, Gothenburg, Sweden
[8] Univ Oslo, Inst Clin Med, Div Med, Oslo, Norway