Brain atrophy and magnetization transfer ratio following methylprednisolone in multiple sclerosis: short-term changes and long-term implications

Background: The short-term effect of corticosteroids on MRI measures of multiple sclerosis (MS) is not well understood and may have a significant impact when using these quantitative measures to evaluate disease activity and changes following other therapeutic interventions. Objective: To determine the impact of a course of intravenous methylprednisolone (IVMP) on quantitative measures of disease activity and tissue injury in MS patients. Methods: We prospectively measured brain parenchymal fraction (BPF), magnetization transfer ratio (MTR, lesional and whole brain), and lesion volumes on nine weekly brain MRI studies in ten MS patients receiving a course of IVMP. A group of nine MS patients not receiving IVMP served as controls. Results: In comparison to untreated controls, BPF declined over the eight weeks following IVMP treatment (P<0.02). BPF decline was most prominent in patients with secondary progressive MS (SPMS, P<0.03), and was not seen in relapsing-remitting (RR) MS patients. Short-term change in BPF correlated with baseline BPF (r=0.62, P=0.05) and short-term change in lesional MTR (r=-0.55, P=0.03), but not with change in enhancing lesion volume. Short-term change in lesional MTR inversely correlated with baseline lesional and whole brain MTR (r=-0.79, P=0.04 for both). There was no significant difference between treated and control patients in measures of MTR or T2, T1 or enhancing lesion volumes. Conclusions: Patients with SPMS showed a greater decline in BPF following IVMP than RRMS patients. A correlation between changes in BPF and MTR suggest that these changes are secondary to altered water content within MS lesions. Differential response to a standardized therapeutic intervention in RRMS and SPMS suggests that responses to therapy may differ due to a fundamental pathologic difference between early and late stage MS.