Accelerated mI/tNAA Increase in Normal-Appearing WM of RRMS with Paramagnetic Rim Lesions: A 7T MR Spectroscopic Imaging 2-year Follow-Up Study

Motivation: Investigating normal-appearing white matter (NAWM) in relapsing-remitting multiple sclerosis (RRMS) with paramagnetic rim lesions (PRLs) using magnetic resonance spectroscopy imaging (MRSI) may clarify shift from RRMS to progressive MS and identify mI/tNAA as biomarker for MS progression. Goal(s): Examine mI/tNAA levels in NAWM over two years and how they are impacted by presence of PRLs using ultra-high-resolution 7T MRSI. Approach: Annually measured mI/tNAA in NAWM was compared across groups (RRMS with >1 PRL and ≤1 PRL, and secondary progressive MS) using linear mixed-effect models. Results: RRMS patients showed rising mI/tNAA, with larger increases in those with multiple PRLs, while SPMS patients remained stable. Impact: Results revealed faster increase in mI/tNAA in the NAWM of patients with >1 PRL, which may indicate elevated inflammation. This could explain the transition from relapsing-remitting MS to progressive forms and identify mI/tNAA as potential biomarker for MS progression.