Background: The influence of the patterns of onset of multiple sclerosis and relapses of the disease on the time course of irreversible disability is controversial.
Methods: In 1844 patients with multiple sclerosis who were followed for a mean (+/- SD) of 11 +/- 10 years, we determined the time of the clinical onset of the disease, the initial course (relapsing-remitting or progressive) and the subsequent course (relapsing-remitting, secondary progressive, or primary progressive), the times of relapses, the time to the onset of irreversible disability, and the time course of progressive, irreversible disability. We used three scores on the Kurtzke Disability Status Scale (range, 0 to 10, with higher scores indicating more severe disability) as measures of the severity and progression of disability: a score of 4 (limited walking ability but able to walk for more than 500 m without aid or rest), a score of 6 (ability to walk with unilateral support no more than 100 m without rest), and a score of 7 (ability to walk no more than 10 m without rest while leaning against a wall or holding onto furniture for support). We used Kaplan-Meier analyses to determine the influence of relapses on the time to the onset of irreversible disability.
Results: The median times from the onset of multiple sclerosis to the assignment of a score of 4, a score of 6, and a score of 7 on the disability scale were longer among the 1562 patients with a relapsing-remitting onset of disease (11.4, 23.1, and 33.1 years, respectively) than among the 282 patients who had progressive disease from the onset (0.0, 7.1, and 13.4 years, respectively; P<0.001 for all comparisons). In contrast, the times from the assignment of a score of 4 to a score of 6 were similar in the two groups (5.7 and 5.4 years, P=0.74). The time course of progressive, irreversible disease among patients with the primary progressive type of multiple sclerosis was not affected by the presence or absence of superimposed relapses.
Conclusions: Among patients with multiple sclerosis, relapses do not significantly influence the progression of irreversible disability.