Multiple sclerosis (MS) is characterized by relapses with or without residual worsening and/or steady progression independent of relapses.
1-4 A consensus statement suggested using the term
disability worsening to describe a stepwise increase in disability in patients with relapsing MS (RMS) while reserving the term
disability progression for patients in the progressive phase of MS, when disability accumulation occurs more continuously and independently of relapse activity.
1 Most clinicians would not consider patients with RMS with a low level of disability to have secondary progressive MS (SPMS), in which accumulation of disability occurs independently of relapse activity,
1 despite mounting data that patients with RMS frequently worsen over time, even when relapse activity appears well controlled.
5-7