MRI correlates of disease course and activity in multiple sclerosis

We have carried out a comparative cross-sectional study of patients with relapsing and remitting MS (multiple sclerosis) (RRMS) (n=9), primary progressive MS (PPMS) (n=7), and secondary progressive MS (SPMS) (n=10) using image analysis techniques to determine the number and volume of Gd-DTPA-enhancing lesions. RRMS patients had more lesions than either PPMS or SPMS (ns), and the mean volume of the lesions (p=0.006) and the total volume of enhancing lesions (p<0.03) were significantly larger in patients with RRMS compared with PPMS. The prevalence of blood-brain barrier (BBB) breakdown appears to be similar in PPMS and SPMS, with the higher rate in RRMS suggesting a suppressive effect of disease duration (and/or age). Similarly, the volume of the lesion load overall was negatively correlated with disease duration (p –0.56,p<0.003). Differences between PPMS and RRMS/SPMS patients in the volume of the enhancing lesions may reflect differences in the ability of these patients to suppress the immune-mediated damage to axons which may follow episodic BBB breakdown and which is not visualized on conventional magnetic resonance imaging.