The Associations Between Chronic Active Lesions and White Matter Disease: A 7 Tesla Imaging Study

The relationship between paramagnetic rim lesions (PRLs) and surrounding normally appearing white matter (NAWM) disease, potentially contributory to the associations seen between PRLs and clinical impairment, is underexplored.

To assess whether PRLs correlate with a greater degree of NAWM injury in early MS.

PRLs were identified on susceptibility weighted imaging (SWI) of 68 newly diagnosed patients. Each PRL was paired with an anatomically matched contralateral non-PRL (nPRL) from the same participant. Quantitative magnetization transfer imaging derived macromolecular-to-free pool-size ratio (PSR) and relaxation rate of the free water pool (R_1f) values were extracted and compared between PRLs and nPRLs, NAWM surrounding PRLs and nPRLs, and whole brain WM lesions and NAWM of PRL+ and PRL- people with MS (pwMS).

PSR and R_1f (p ≤ 0.028) values were lower in PRLs compared to nPRLs, but there were no differences in PSR and R_1f (p ≥ 0.824) values between peri-PRLs and peri-nPRLs NAWM ROIs. PRL+ pwMS had similar PSR and R_1f (p ≥ 0.267) of the whole brain NAWM, similar WM lesions PSR (p = 0.764) but lower R_1f (p = 0.030) values.

In the early stages of MS, there is no association between PRLs and surrounding NAWM degree of injury.