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.