Hey there. Tysabri is a disease modifying therapy that aims to slow progression. Docs monitor your brain with MRIs (usually 1 every 6 months). From those, they can see if your ms is active or if it is not. If there is no new progression you can attribute some of that success to Tysabri. Hope this helps

@Shsy_x0 The quick answer from your perspective is, you don't have a relapse that negatively affects the quality of your life. From the neurologist's perspective, because you don't have a relapse, it means the MS is not active (dormant). Neurologists usually confirm if the MS is either dormant - effective DMT, or active when they read the MRI results. Good luck!