Relapsing-remitting multiple sclerosis: sequential enhanced MR imaging vs clinical findings in determining disease activity.

OBJECTIVE: Sequential MR imaging frequently shows disease activity (clinically silent new brain lesions) in subgroups of patients with multiple sclerosis and therefore is valuable in monitoring the effects of treatment. Monitoring of disease activity in patients being treated for relapsing-remitting multiple sclerosis will increase in importance as new and safe therapies are developed. We studied sequential enhanced MR images of patients with early relapsing-remitting multiple sclerosis to define the MR features that indicate disease activity in this subgroup of patients and to compare MR imaging and clinical findings for this purpose. SUBJECTS AND METHODS: Seven patients with relapsing-remitting definite multiple sclerosis were examined monthly for 4-12 months. For each image, a standard repositioning protocol consisting of three images was used to ensure reproducibility of axial (double oblique) image planes, planned according to internal landmarks. A total of 58 unenhanced T2-weighted and enhanced T1-weighted MR images were obtained. RESULTS: MR images showed new enhancing lesions in six of the seven patients. On 25 (43%) of the 58 enhanced T1-weighted MR images, a total of 50 new enhancing lesions were observed, and on one image a reenhancing lesion was seen. The unenhanced T2-weighted images showed corresponding abnormalities for 92% of the new enhancing lesions. At follow-up, most lesions (86%) were enhanced on only one occasion: 4% were enhanced on more than two consecutive monthly MR examinations. Forty-nine percent of the lesions seen on T2-weighted images "disappeared" (beyond the resolution of the imaging system) after a mean follow-up of 3.5 months, especially lesions that were initially smaller than 5 mm. During the study, only five clinical relapses occurred in three patients (all at times when MR images showed contrast-enhancing lesions), and fixed disability did not increase. On 21 additional occasions, MR images showed new enhancing or reenhancing lesions in patients who were clinically stable at the time (4.2 times more clinically silent disease activity). CONCLUSION: Our results suggest that contrast-enhanced MR imaging is more sensitive than clinical monitoring for detecting new disease activity in patients with relapsing-remitting multiple sclerosis and that MR imaging might be useful in the evaluation of therapeutic regimens.