1. Department of Neurology, Aegintion Hospital, Medical School of Athens, Greece
2. Folkhälsan Institute of Genetics and Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland
3. Neuromuscular Research Center, University of Tampere and Tampere University Hospital, Tampere, Finland
4. Department of Neurology, Vaasa Central Hospital, Vaasa, Finland