1 Department of Neurology, Oslo University Hospital, Ullevål and Institute of Health and Society, Faculty of Medicine, University of Oslo, Oslo, Norway.
2 Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
3 Department of Neurology, Clinic of Optic Neuritis and Clinic of Multiple Sclerosis, Rigshospitalet Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.