Benign and secondary progressive multiple sclerosis: a preliminary quantitative MRI study

In a preliminary study, we compared by means of quantitative magnetic resonance imaging (MRI) methods (1) the T2 values and the decay charcteristics of chronic brain lesions, (2) the T2 values of normal- appearing frontal white matter (NAWM) and (3) brain lesion volumes in patients with benign and secondary progressive multiple sclerosis (MS) in order to evaluate the mechanisms underlying the de- velopment of disability. Eleven clini- cally definite MS patients with either benign MS (n = 5) or secondary pro- gressive MS (n = 6) were studied. Fifty-two chronic lesions (identified by comparison with MRI scans ob- tained at least 12 months previously) were identified. The mean T2 of large lesions (cross-sectional area greater than 41 mm a) and of the NAWM was similar in both clinical groups. However, small lesions hadhigher mean T2 values (P < 0.01) in the benign group, probably at least in part because of partial volume ef- fects. Analysis of large lesions re- vealed biexponential T2 relaxation in 6 of 8 "secondary progressive" and in 2 of 16 "benign" lesions, perhaps indicating a greater degree of axonal loss in large lesions of patients with secondary progressive MS. Patients with secondary progressive MS had higher (although not significant) total and infratentorial lesion loads than those of the benign group. These preliminary findings suggest, but do not establish, that variations in the extent, site and pathological nature of lesions may all contribute to dif- ferent patterns of disease evolution in MS