Serial contrast-enhanced MR in patients with multiple sclerosis and varying levels of disability.

PURPOSE To compare the rates of enhancement and changes in lesion burden in patients with multiple sclerosis (MS) and varying levels of disability.

METHODS Monthly enhanced MR images of the brain were obtained for 6 months from seven patients with mildly disabling relapsing-remitting MS and from seven patients with secondary progressive MS and severe disability. At entry and 1 year later, two unenhanced T2-weighted images of the brain were also obtained.

RESULTS Despite the fact that both groups had clinically active disease and had similar increases in unenhanced MR lesion load, the total number of enhancing lesions was 239 in patients with relapsing-remitting MS (42 on the baseline images, 151 new and 46 persistent during follow-up) (average number of lesions per patient per year was 68) and 21 in those with secondary progressive MS (five on the baseline images, 13 new, and three persistent during follow-up) (average number of lesions per patients per year was seven).

CONCLUSION Our data indicate that the rate of enhancement significantly decreases in the more advanced phases of MS. This is important when planning clinical trials, and suggests that mechanisms underlying lesion formation might be dissimilar in different MS patient groups.