Temporal evolution of remission following multiple sclerosis relapse and predictors of outcome

Background: Relapse is a characteristic clinical feature of multiple sclerosis (MS) and is commonly employed as a measure of efficacy following therapeutic intervention. However, less is known about the temporal evolution of subsequent disability or factors predicting recovery. Objectives: The objective of this study was to assess the pattern of recovery following relapse and identify factors which predict recovery and residual disability following relapse. Methods: A total of 226 relapses were studied prospectively in a cohort of 144 patients with standardised clinical assessments of physical disability including Expanded Disability Status Scale (EDSS), 10-m timed walk, 9-hole peg test and Multiple Sclerosis Impact Scale (MSIS-29) at 0, 2, 6 and 12 months. A total of 82 patients completed 12 months of follow up without further relapse. Results: Thirty per cent of relapses were severe (change in EDSS >2.0) of which 11% failed to recover. All measures showed significant improvement at 2 months but additional improvement was also observed in 9-hole peg test and MSIS-29 up to 12 months following initial assessment. Mean time to second relapse was 382 days. The only predictor of relapse severity in the model tested was younger age; however, increasing age and initial relapse severity were also predictors of poor outcome. Conclusions: This study shows that the majority of improvement in physical disability following relapse occurs by 2 months but that more subtle recovery can take place over 12 months in a small sub-group of patients. These data will aid in patient counselling and will also inform the timing of therapeutic intervention and physical support