Levodopa-associated shifts in motor asymmetry and axial burden in Parkinson’s disease: a retrospective cross-sectional study comparing patients with and without STN-DBS

BACKGROUND: Motor asymmetry and axial symptoms represent partially distinct dimensions of the Parkinson's disease (PD) motor phenotype. Although subthalamic nucleus deep brain stimulation (STN-DBS) and dopaminergic therapy are known to influence motor presentation, the clinical expression of lateralized and axial motor domains under different treatment strategies remains incompletely characterized in real-world settings. OBJECTIVES: To compare motor asymmetry and axial involvement between PD patients treated with STN-DBS and those receiving medical therapy alone, and to examine OFF - ON levodopa-related modulation of these motor domains. METHODS: In this retrospective cross-sectional study, 184 consecutive PD patients (44 with STN-DBS and 140 without DBS) underwent standardized evaluations in medication 'OFF' and 'ON' states. Motor Asymmetry Index (MAI) and Axial-to-Appendicular Ratio (AAR) were calculated using MDS-UPDRS-III subscores. Between-group comparisons and within-group OFF - ON changes were analyzed, adjusting for disease duration and baseline motor severity. RESULTS: < 0.01). The magnitude of AAR change was greater in the STN-DBS cohort. CONCLUSIONS: In this retrospective cross-sectional study, levodopa was associated with a shift in motor phenotype characterized by increased asymmetry and axial-to-appendicular burden, independent of DBS status. These findings suggest that dopaminergic therapy may reshape motor expression rather than uniformly improve motor function.