The influence of dopaminergic medication on balance automaticity in Parkinson's disease.

Background: Studies have shown that dual-task standing balance in Parkinson's disease (PD) is significantly diminished. Additionally, it is well accepted that dopaminergic medication improves dynamic balance (Berg Balance Scale, mini-BESTest), but standing balance (force platform posturography) may suffer. What remains unknown is how dopaminergic medication influences standing balance automaticity in PD.

Research Question: Does dopaminergic medication improve standing balance automaticity during a phoneme monitoring dual-task in PD?

Methods: This was a cross-sectional study. Sixteen subjects with PD completed single- and dual-task standing with eyes open and eyes closed for 3 min each in off and on medication states. 95% confidence ellipse area, anterior-posterior sway velocity, medial-lateral sway velocity, and integrated time to boundary were calculated. Data were analyzed with a repeated measures ANOVA.

Results: Dopaminergic medication significantly increased ellipse area (p =  0.002) and decreased the performance on the secondary task (p =  0.004). Different eyes conditions (open vs. closed) significantly increased both sway velocities (anterior-posterior = p <  0.001, medial-lateral = p <  0.001), and increased integrated time to boundary (p <  0.001). There were also task by eyes condition interaction effects for anterior-posterior velocity and integrated time to boundary (p =  0.015 and p =  0.009, respectively). Increases in sway velocity and integrated time to boundary seen in the eyes condition and interaction effects are traditionally interpreted as poorer balance performance. However, in the context of stability/maneuverability tradeoff, the changes may indicate an increase in freedom of movement instead of a decrease in stability.

Significance: The data did not support a medication-induced improvement in automaticity, as measured by significant medication by task interactions. An alternate interpretation for medication-induced balance changes in PD includes an increase in maneuverability without sacrificing stability after taking dopaminergic medication.