13th Annual Meeting of the Amer-Comm-for-Treatment-and-Res-in-Multiple-Sclerosis/24th Congress of the European-Comm-for-Treatment-and-Res-in-Multiple-Sclerosis/5th Congress of the Latin-Amer-Comm-for-Treatment-and-Res-in-Multiple-Sclerosis, Montreal, Canada, 17 - 20 September 2008, vol.14