Structural Brain Plasticity in Chronic Stroke: Cerebellar Remodeling and Its Association With Upper Limb Motor Outcome.

Neuronal plasticity after stroke occurs predominantly within the first few months. However, its persistence and distribution in the chronic phase remain unclear. This study investigated longitudinal changes in cortical gray matter and corticospinal tract integrity beyond 6 months poststroke and their associations with chronic upper limb motor outcomes. We conducted a retrospective cohort study at St. Vincent's Hospital (Suwon, Republic of Korea) between 2015 and 2022, including patients with first-ever unilateral stroke who underwent at least 2 magnetic resonance imaging scans ≥6 months post-onset. Gray matter volume in cerebral and cerebellar cortices was assessed using 3-dimensional T1-weighted imaging and corticospinal tract integrity via diffusion tensor tractography. Hemispheres were classified as affected or unaffected based on anatomic connectivity to the lesion. Upper limb motor score was measured using a 5-stage ordinal scale and grouped into 3 categories by hand function: poor (no movement), partial (limited movement), and good (fully functional use). Ordinal logistic regression identified structural predictors of motor outcomes, adjusting for age, sex, lesion volume, and baseline impairment. Among 62 patients, structural plasticity persisted beyond 6 months in a subset of patients. Imaging was conducted at an average of 51 months poststroke (range, 13-137 months). Increases in affected cerebellar gray matter were associated with better motor outcomes (odds ratio, 0.67 [95% CI, 0.48-0.92]; P=0.01). The odds ratio <1 indicates lower odds of poor outcomes. No significant associations were found for other brain regions or corticospinal tract integrity. Cerebellar remodeling may support long-term motor recovery after stroke.