Effect of relapses on development of residual deficit in multiple sclerosis

Objective: To determine the percentage of patients with residual deficits following multiple sclerosis ( MS) exacerbations and the magnitude of those deficits using a database of pooled placebo patients from clinical trials. Methods: A database of patients assigned to the placebo group in several randomized clinical trials was queried to determine those patients with Expanded Disability Status Scale ( EDSS) and Scripps Neurologic Rating Scale assessments prior to, at the time of, and after an acute exacerbation of MS. The extent of deficit present at these time points was compared to determine the acute effect of exacerbations and the degree of persistent disability. Results: Forty- two percent of patients had residual deficit of at least 0.5 and 28% had residual of greater than or equal to 1.0 EDSS units, at an average of 64 days after an exacerbation. The results were reproduced across subsequent exacerbations and were sustained over time. The subgroup of patients with measurable change in EDSS during the exacerbation had more extensive residual impairment on the follow- up visits. Similar results were seen when the Scripps score was examined. Conclusion: MS exacerbations produce a measurable and sustained effect on disability.