Assessment of Cortical Myelination in Patients with MS via T1-Weighted/FLAIR Ratio: A Longitudinal Follow-Up Study

<h3>PURPOSE:</h3> The T1-weighted (T1W)/FLAIR ratio may reflect cortical myelin integrity in patients with MS (PwMS). This study aimed to investigate the longitudinal significance of the cortical T1W/FLAIR ratio in PwMS. <h3>MATERIALS AND METHODS:</h3> Brain MRI data were obtained from PwMS and patients with clinically isolated syndrome (CIS) between September 2021 and December 2023. 3D T1W and FLAIR images were preprocessed to calculate gray matter (GM) and superficial white matter (WM) T1W/FLAIR ratios across cerebral regions. Baseline and follow-up MRI scans were analyzed for T1W/FLAIR ratio changes and correlations with clinical parameters (Expanded Disability Status Scale [EDSS] and disease duration). Cortical T1W/FLAIR ratio changes were compared with WM lesion changes (new, developing, or decreased lesions) on follow-up MRI scans. <h3>RESULTS:</h3> In total, 63 patients with MS and 5 patients with CIS (mean age: 40.5 years; 73.5% women) were evaluated. The median baseline EDSS score was 1.5, and median MRI interval was 13.5 months. GM T1W/FLAIR ratio changes were negatively correlated with EDSS changes in superficial GM of the whole brain (<i>r</i> = −0.201, <i>P</i> = .02, positive false discovery rate [pFDR] =0.1) and occipital cortex (<i>r</i> = −0.269, <i>P</i> = .002, pFDR =0.01). Patients with stable or improved EDSS scores exhibited significant GM T1W/FLAIR ratio increases (<i>P</i> = .04 and <i>P</i> &lt; .001, respectively). T1W/FLAIR ratio changes were positively correlated with disease duration (<i>r</i> = 0.285, <i>P</i> = .02) but not WM lesion changes. <h3>CONCLUSIONS:</h3> Longitudinal GM T1W/FLAIR ratio changes were associated with disease severity in PwMS, supporting its potential role as a potential biomarker for cortical myelination and disease monitoring.