Residual disability after severe relapse in people with multiple sclerosis treated with disease-modifying therapy

Background: The rate of post-relapse residual disability in patients with relapsing–remitting multiple sclerosis (RRMS) treated with disease-modifying drugs (DMD) has not been studied. Objective: To assess relapse residual disability in DMD-treated RRMS patients. Methods: We followed DMD-treated RRMS patients presenting with acute relapse who received high-dose steroids. Increases in Expanded Disability Status Scale (EDSS) of at least 2.0, 1.0–1.5 or 0.5 were defined as severe, moderate or mild relapses, respectively. The proportions of patients with post-relapse residual disability defined as the failure to regain pre-relapse neurological status at 1, 4 and 12 months were evaluated. Results: Out of 1672 relapses in DMD-treated RRMS patients, 17% were severe. In patients who presented with a severe relapse, we observed post-relapse residual disability of at least 1.0 EDSS point in 60.1%, 55.9% and 48.2% of patients at 1, 2 and 12 months of follow-up, respectively. Post-relapse residual disability of at least 2.0 EDSS points was observed in 37.4%, 30.7% and 20.7% of patients after 1, 2 and 12 months, respectively. Conclusion: A high rate of incomplete recovery was seen 12 months following severe relapse among RRMS patients and may contribute to the accumulation of long-term disability.