[1] Univ Helsinki, Dept Med Genet, Folkhalsan Inst Genet, Helsinki, Finland
[2] Seinajoki Cent Hosp, Dept Neurol, Seinajoki, Finland
[3] Tampere Univ Hosp, Ctr Lab Med, Dept Pathol, Tampere, Finland
[4] Univ Hosp, Neuromuscular Res Ctr, Tampere, Finland
[5] Univ Tampere, Dept Neurol, FIN-33101 Tampere, Finland
[6] Univ Oulu, Dept Neurol, Oulu, Finland