CORRELATING MRI AND CLINICAL-DISEASE ACTIVITY IN MULTIPLE-SCLEROSIS - RELEVANCE OF HYPOINTENSE LESIONS ON SHORT-TR SHORT-TE (T-1-WEIGHTED) SPIN-ECHO IMAGES

Magnetic resonance imaging (MRI) is being used as an outcome criterion in therapeutic trials in multiple sclerosis (MS) on the assumption that it, as a sensitive marker of biologic disease activity, could serve as a surrogate marker of disability. We evaluated the relation between MRI findings and disability in a quantitative followup study of 48 MS patients. Median duration of follow-up was 24 months (range, 10 to 42 months). Computer-assisted volume measurements employing a seed-growing technique yielded a standard error of measurement of 0.275 cm(2). The median total area of the hyperintense lesions on the initial T-2-weighted images was 8.4 cm(2). The median increase was 0.76 cm(2)/yr (9%). In a subgroup (n = 19) with short-TR/short-TE spin-echo (SE) images, we measured the hypointense lesion load. The median total area of the lesions at entry was 0.70 cm(2), with a median increase of 0.28 cm(2)/yr (40%). The total area of the hyperintense lesions on the initial T-2-weighted images showed a weak correlation with the Expanded Disability Status Scale score at entry (Spearman rank correlation coefficient [SRCC] = 0.30; 0.02 <p < 0.05). The increase in disability showed a positive correlation (SRCC = 0.19) with the increase in hyperintense lesion load on the T-2-weighted SE images, but this correlation did not reach statistical significance (p = 0.09), probably because of lack of clinical progression. The number of active lesions detected by visual analysis of the T-2-weighted SE images correlated significantly (SRCC = 0.40; 0.001 < p < 0.01) with the number of relapses during the interval between the initial and follow-up imaging examinations. The subgroup with short-TR/short-TE SE images (whose disease was clinically more active than the group as a whole) showed a significant correlation of increased disability with increase in hypointense lesion load (SRCC = 0.74; p < 0.002). Our results, and those from previous follow-up studies, suggest a positive correlation between MRI and clinical activity, but extended follow-up studies are needed to confirm the appropriateness of quantitative MRI as a surrogate marker of disability in MS. Short-TR/short-TE SE images seem to be more relevant than T-2-weighted SE images in identifying the lesions that cause disability.