Characterization of chronic active multiple sclerosis lesions with sodium ( Na) magnetic resonance imaging-preliminary observations.

Background And Purpose: There has been an increasing interest in chronic active multiple sclerosis (MS) lesions as a new magnetic resonance imaging (MRI) marker of disease progression. Chronic active lesions are characterized by progressive tissue matrix damage, axonal loss and chronic inflammation. Sodium ( Na) MRI provides a biochemical marker of cell integrity and tissue viability in a quantitative manner. The aim of this study was to investigate with Na MRI tissue abnormalities in chronic active lesions as indicators of tissue destruction.

Methods: To identify chronic active lesions, two 3D magnetization-prepared rapid acquisition gradient-echo datasets obtained 12 months apart were processed using the voxel-guided morphometry algorithm. Cross-sectional Na MRI was performed during the 12-month follow-up period. Total sodium concentration was calculated in chronic active lesions compared to shrinking, chronic stable and acute contrast-enhancing lesions.

Results: Overall, 70 MS lesions (21 chronic active, 10 shrinking, 29 chronic stable lesions, 10 acute contrast-enhancing lesions) in 12 patients were included. Total sodium concentration in chronic active lesions (49.57 ± 8.47 mM) was significantly higher than in shrinking (42.16 ± 3.9 mM; p = 0.03) and chronic stable lesions (39.92 ± 4.82 mM; p < 0.001). Chronic active lesions showed similar sodium values compared to acute contrast-enhancing lesions (48.06 ± 6.65 mM; p = 0.97). No differences between shrinking and chronic stable lesions were observed (p = 0.89).

Conclusion: High sodium values in chronic active MS lesions may be an indicator of ongoing inflammation and tissue damage.