Assessment of postural stability in various stages of Parkinson's disease

Abstract

Background: Most studies compare Parkinson's disease (PD) patients with healthy people, but no study has compared postural stability between all four stages of the disease. It remains unclear how patients at different stages use vision and proprioception to maintain balance. This study aimed to evaluate these differences. Methods: We studied 39 PD patients in four severity groups and 40 healthy matched subjects. All stood on a force plate for 60 s. We tested four conditions: eyes open/closed on a solid surface and on a foam pad. Postural stability was evaluated by excursion, velocity and root mean square of Center of Pressure. A mixed ANOVA (5 & times; 2 & times; 2) was used for final analysis. Results: The effect of closing the eyes on balance depended on the surface and disease stage (group & times;vision & times;surface interaction, p < 0.033). In patients with stage 2 PD and healthy subjects, closing the eyes increased sway significantly only on foam (p < 0.007). In contrast, stage 3 PD patients showed a significant increase in sway only on a solid surface when their eyes were closed (p < 0.000). Stage 4 PD patients showed little change in sway across all conditions. Conclusion: Patients in different stages use different strategies to control balance. The most notable finding was that stage 3 patients become overly dependent on vision even when proprioceptive input should be sufficient. This suggests that balance assessments should challenge both sensory systems, and rehabilitation programs should be tailored to the specific stage of the disease.