Association of visually assessed putaminal and infratentorial MRI signs with motor symptoms in multiple system atrophy: a cross-sectional study

Abstract Background Visual MRI signs are widely used in multiple system atrophy (MSA), but their clinical correlates remain incompletely defined. We examined the concordance of visually assessed putaminal MRI markers and their associations with contralateral parkinsonian features, together with the relationship between infratentorial signs and cerebellar dysfunction. Methods In this retrospective cross-sectional study, 94 patients with clinically established or clinically probable MSA (50 MSA-P, 44 MSA-C), classified according to the 2022 Movement Disorder Society criteria, underwent 3.0-T MRI. Visual markers included putaminal rim scores on diffusion-weighted imaging (DWI) and susceptibility-weighted imaging (SWI), lateral apparent diffusion coefficient (ADC) hyperintensity, and infratentorial signs. Imaging-clinical associations were examined using unadjusted analyses, age- and subtype-adjusted models, side-combined generalized estimating equation (GEE) models, and exploratory asymmetry analyses. Results Side-specific motor scores were available for 51/94 patients and heel-knee-shin scores for 49/94. Putaminal abnormalities were more frequent in MSA-P, whereas infratentorial signs were more frequent in MSA-C. Inter-rater agreement was substantial for visual MRI markers. ADC hyperintensity showed moderate agreement with dichotomized DWI/SWI abnormalities (κ = 0.400-0.617), whereas DWI and SWI scores were strongly correlated (ρ = 0.718–0.730; p < 0.001). Unadjusted analyses suggested associations between left ADC hyperintensity and higher contralateral motor scores. In age- and subtype-adjusted models, separate side-specific putaminal models did not show significant associations with contralateral total lateral motor score, and infratentorial sign models did not show significant associations with heel-knee-shin score. However, in side-combined GEE models adjusted for age, MSA subtype, and imaging side, ADC hyperintensity and higher DWI/SWI rim scores were associated with higher contralateral total lateral motor scores ( p = 0.004, p = 0.017, and p = 0.015, respectively). Conclusions Structured visual MRI assessment provides reproducible information for phenotypic characterization within MSA. Side-combined GEE findings suggest putaminal imaging-motor associations, but incomplete clinical assessments limit generalizability. The diagnostic value of these signs requires evaluation in comparator cohorts.