Five-year longitudinal changes in quantitative spinal cord MRI in multiple sclerosis.

BACKGROUND

The spinal cord (SC) is highly relevant to disability in multiple sclerosis (MS), but few studies have evaluated longitudinal changes in quantitative spinal cord magnetic resonance imaging (SC-MRI).

OBJECTIVES

The aim of this study was to characterize the relationships between 5-year changes in SC-MRI with disability in MS.

METHODS

In total, 75 MS patients underwent 3 T SC-MRI and clinical assessment (expanded disability status scale (EDSS) and MS functional composite (MSFC)) at baseline, 2 and 5 years. SC-cross-sectional area (CSA) and diffusion-tensor indices (fractional anisotropy (FA), mean, perpendicular, parallel diffusivity (MD, λ, λ) and magnetization transfer ratio (MTR)) were extracted at C3-C4. Mixed-effects regression incorporating subject-specific slopes assessed longitudinal change in SC-MRI measures.

RESULTS

SC-CSA and MTR decreased ( = 0.009,  = 0.03) over 5.1 years. There were moderate correlations between 2- and 5-year subject-specific slopes of SC-MRI indices and follow-up EDSS scores (Pearson's with FA = -0.23 ( < 0.001); MD = 0.31 ( < 0.001); λ = 0.34 ( < 0.001); λ = -0.12 ( = 0.05), MTR = -0.37 ( < 0.001); SC-CSA = -0.47 ( < 0.001) at 5 years); MSFC showed similar trends. The 2- and 5-year subject-specific slopes were robustly correlated ( = 0.93-0.97 for FA, λ, SC-CSA and MTR, all s < 0.001).

CONCLUSION

In MS, certain quantitative SC-MRI indices change over 5 years, reflecting ongoing tissue changes. Subject-specific trajectories of SC-MRI index change at 2 and 5 years are strongly correlated and highly relevant to follow-up disability. These findings suggest that individual dynamics of change should be accounted for when interpreting longitudinal SC-MRI measures and that measuring short-term change is predictive of long-term clinical disability.