Multiple sclerosis (MS) is an intractable inflammatory neurodegenerative disease that exhibits variable progression among individuals. This condition is classified as relapsing–remitting, secondary progressive, or primary progressive (Confavreux and Vukusic, 2006). Both pathophysiology and treatment strategies vary by subtype (Filippi et al., 2018). However, there are no sufficient biomarkers to distinguish between RRMS and SPMS (Ferrazzano et al., 2021).

The glymphatic system is a recently proposed mechanism for waste clearance in the brain, which compensates for the lack of lymphatic tissue. One of the imaging techniques used in this system is diffusion tensor image analysis along the perivascular space (DTI-ALPS), which is helpful for evaluating glymphatic function or interstitial fluid dynamics (Taoka et al., 2017). This technique has been applied not only in degenerative diseases such as Alzheimer's disease but also in MS (Carotenuto et al., 2022) and neuromyelitis optica spectrum disorder (Cacciaguerra et al., 2022).

This study compared the DTI-ALPS index between SPMS and RRMS to investigate the differences in their pathologies and determine their utility as biomarkers. This study is positioned as a pilot study due to its examination of a relatively small number of cases in a single facility.