5-10% is the fatality rate for this procedure. You can see the authors of this study were at a number of sites in the US, Canada, Spain and Austria. I would expect the fatality rate to be higher in a group of people with higher EDSS and longer duration of disease. That is why they limit participation in the Canadian trial to people early in disease course and must be ambulatory.
I no longer qualify for the study because I no longer have clear attacks and remissions, and i am 7 years since onset.