Associations between different types of chronic lesions and gray matter atrophy in multiple sclerosis

Focal lesions are one of the key factors contributing to brain atrophy in multiple sclerosis (MS) patients. This study aimed to investigate the associations between the different types of chronic lesions and gray matter atrophy in MS patients. The study recruited MS patients from two institutions, along with healthy controls (HCs). Lesions were classified into paramagnetic rim lesions (PRLs) and non-PRLs. Lesion volume, diffusion kurtosis imaging (DKI) parameters, brain volume (BV), gray matter volume (GMV), and cortical thickness (CT) were extracted. Differences between PRLs and non-PRLs, as well as between MS and HC groups, were analyzed. The associations between lesions and brain structure features were assessed using a general linear model. The study included 46 relapsing-remitting multiple sclerosis (RRMS) patients and 31 HCs. A total of 940 chronic lesions were collected, of which 382 were PRLs (41%) and the remainder were non-PRLs. PRLs had larger volume and lower DKI parameters compared to non-PRLs. The MS group showed reduced GMV and CT compared to the HC group. The volume of all lesion types was negatively correlated with brain structure features, while some DKI parameters showed positive correlations. The Kr value of non-PRLs, the Kr value of whole lesions, and the volume of whole lesions were most strongly correlated with GMV, BV, and CT, respectively. Both the volume and microstructural damage of chronic MS lesions are associated with gray matter atrophy. Contrary to expectations, the microstructural impairment of non-PRLs showed a stronger association with atrophy than that of the more destructive PRLs. This highlights the need to pay more attention to the role of non-PRLs in disease progression.