1. Department of Neurology, Akershus University Hospital, Lørenskog, Norway
2. Institute of Clinical Medicine, Univeristy of Oslo, Oslo, Norway
3. Norwegian Multiple Sclerosis Competence Centre, Department of Neurology, Haukeland University Hospital, Bergen, Norway
4. Department of Clinical Medicine, University of Bergen, Bergen, Norway
5. Department of Neurology, Haukeland University Hospital, Bergen, Norway