This is a prospective, observational, single-blinded, longitudinal study of natalizumab effect on brain atrophy development and disability progression in multiple sclerosis patients over 5 years, which will evaluate originally treated patients with natalizumab who participated in a prospective 1- and 2-year VWMTR study. (Zivadinov et al., 2011b) All subjects will be assessed at 5-year follow-up with the same clinical examinations and will obtain 1.5T MRI examination on the same scanner that did not undergo any upgrade changes in the period of 5 years.
