ABSTRACT NUMBER: ESOC2026A2383 LONGITUDINAL DIFFUSION SIGNATURES OF WHITE MATTER MICROSTRUCTURE FOLLOWING CEREBELLAR STROKE

Abstract Background and aims Mechanisms underlying cerebellar stroke (CS) recovery remain incompletely understood, as conventional MRI may miss subtle microstructural changes in normal-appearing tissue. Advanced diffusion imaging enables longitudinal assessment of white matter integrity beyond infarcted tissue. We aimed to characterize longitudinal diffusion trajectories in lesioned and contralesional cerebellar white matter following CS compared with supratentorial stroke (STS). Methods Fourteen subacute ischemic stroke participants (mean age 65.4±11.5 years) were imaged via multi-shell diffusion protocol at 1 and 6 months post-stroke. Diffusion tensor imaging metrics included mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), along with a non-Gaussian diffusion metric of tissue complexity. Four participants had CS and ten had STS. Longitudinal changes in lesioned and contralesional cerebellar white matter were compared between groups alongside Montreal Cognitive Assessment (MoCA) scores. Results MoCA scores did not differ between CS and STS at either time point; however, longitudinal change trended toward improvement in CS and decline in STS (p = 0.052). CS participants exhibited significantly greater increases in AD, RD, and MD within infarcted cerebellar white matter compared with STS (p < 0.05; Fig. 1). Non-Gaussian diffusion analysis identified a significant contralesional cerebellar cluster with increased tissue complexity in CS (p < 0.05; Fig. 2). Conclusions Advanced diffusion imaging revealed longitudinal microstructural trajectories following cerebellar stroke. While conventional DTI detected increased diffusivity within affected tissue, non-Gaussian diffusion uniquely identified contralesional complexity changes, suggesting evolving tissue heterogeneity and possible compensatory remodeling. These findings underscore the sensitivity of advanced diffusion metrics to cerebellar white matter dynamics during recovery. Conflict of interest For all authors: nothing to disclose Figure 1 - belongs to Results Figure 2 - belongs to Conclusions