Balance in Parkinson's disease under static and dynamic conditions

We tested balance performance in 15 on phase Parkinson's disease (PD) patients (8 nonfallers, PD-NF; 7 fallers, PD-F) during quiet stance (stabilometry) and on a platform continuously moving in the anteroposterior direction (dynamic test). Neither stabilometry (eyes open or closed) nor the dynamic test (eyes open) separated PD-F from PD-NF. With the dynamic test, eyes closed, PD-F with respect to PD-NF showed larger head oscillations, smaller cross-correlation between head and malleolus motion (more so in patients with low Unified Parkinson's Disease Rating Scale, or UPDRS), and larger delays of head with respect to platform motion. Further, across all PD patients, head displacement increased with the equivalent levodopa dose, indicating a trend for medication to worsen balancing capacity while improving UPDRS. The dynamic test is a sensitive tool for detecting instability in PD-F since absence of visual flow selectively impairs both association between body segment movements and anticipatory adjustments.