Spatiotemporal gait parameters during turning differ in Parkinson's disease patients with and without freezing of gait.

Introduction: Turning is a complex locomotor task that can accentuate gait impairments and precipitate freezing of gait (FOG) in Parkinson's disease (PD). However, gait-derived spatiotemporal parameters during inter-episodic turning remain incompletely characterized. We compared turning-related gait patterns among healthy older adults, patients with PD without FOG, and patients with PD and a history of FOG. Methods: Ten healthy older controls, 10 patients with PD without FOG (PD-P), and 10 patients with PD and FOG (FOG-P) performed 90°, 180°, and 360° turns while undergoing optical motion capture. Spatiotemporal gait parameters were analyzed using Bayesian generalized linear models. Trials containing observable FOG episodes were excluded; consequently, the analyses represent inter-episodic turning rather than freezing episodes themselves. Results: Compared with controls, PD-P participants demonstrated reduced stride width of the internal leg and increased stride width of the external leg, whereas FOG-P participants demonstrated shorter step and stride lengths. Both PD groups predominantly used step-out or mixed turning strategies and required more time and steps to complete larger-amplitude turns. Discussion: Gait-derived spatial parameters during turning differed between the PD groups. PD-P participants showed more pronounced mediolateral foot-placement differences, whereas FOG-P participants showed more pronounced reductions in anteroposterior step and stride length. Because the groups differed in overall motor severity and the analyses were intentionally restricted to inter-episodic turning, these findings should be interpreted as descriptive turning gait patterns in patients with a history of FOG rather than as evidence of FOG-specific mechanisms.