| Completed | N/A | 30 | Europe | TCD baseline, Transcranial doppler, TCD after bosentan administration, Tracleer, Endothelin-1 receptor antagonist, NIRS baseline, Near-infrared spectroscopy, ForeSight, NIRS after bosentan administration, Near-infrared Spectroscopy | Universitair Ziekenhuis Brussel | Multiple Sclerosis | 03/15 | 04/15 | | |