Magnetic resonance disease severity scale (MRDSS) for patients with multiple sclerosis: a longitudinal study.

BACKGROUND: We previously described a composite MRI scale combining T1-lesions, T2-lesions and whole brain atrophy in multiple sclerosis (MS): the magnetic resonance disease severity scale (MRDSS).

OBJECTIVE: Test strength of the MRDSS vs. individual MRI measures for sensitivity to longitudinal change.

METHODS: We studied 84 MS patients over a 3.2±0.3 year follow-up. Baseline and follow-up T2-lesion volume (T2LV), T1-hypointense lesion volume (T1LV), and brain parenchymal fraction (BPF) were measured. MRDSS was the combination of standardized T2LV, T1/T2 ratio and BPF.

RESULTS: Patients had higher MRDSS at follow-up vs. baseline (p<0.001). BPF decreased (p<0.001), T1/T2 increased (p<0.001), and T2LV was unchanged (p>0.5). Change in MRDSS was larger than the change in MRI subcomponents. While MRDSS showed significant change in relapsing-remitting (RR) (p<0.001) and secondary progressive (SP) phenotypes (p<0.05), BPF and T1/T2 ratio changed only in RRMS (p<0.001). Longitudinal change in MRDSS was significantly different between RRMS and SPMS (p=0.0027); however, change in the individual MRI components did not differ. Evaluation with respect to predicting on-study clinical worsening as measured by EDSS revealed a significant association only for T2LV (p=0.038).

CONCLUSION: Results suggest improved sensitivity of MRDSS to longitudinal change vs. individual MRI measures. MRDSS has particularly high sensitivity in RRMS.