1. Department of Neurology, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel (VUB), Center for Neurosciences, Brussels, Belgium
2. National Multiple Sclerosis Center, Melsbroek, Belgium
3. Department of Neurology, Cliniques Universitaires Saint-Luc, Brussels, Belgium
4. Faculté de Psychologie et des Sciences de l'Education, Mons, Belgium
5. Department of Neurology, Universitair Medisch Centrum Groningen, Groningen, The Netherlands.