Levodopa-induced dyskinesia provokes inflexible head-pelvis coordination during standing in Parkinson's disease.

backgroundTo achieve postural control, individuals must orient their body segments to each other and maintain equilibrium with gravity. However, levodopa, the standard and most effective medication for the symptomatic treatment of Parkinson's disease (PD), also increases postural sway and head instability in people with levodopa-induced dyskinesia (LID). LID is characterized by involuntary, uncontrollable movements occurring after levodopa intake. This study investigated the effect of LID on body segment coordination while standing in PD.

methodsPeople with PD (13 with LID, 12 without LID) and 10 healthy controls (HC) completed 30-second standing trials in single (quiet standing) and cognitive dual-task conditions. Participants with PD completed these trials both in their practical OFF and ON medication states. We recorded head and pelvis acceleration with body-worn inertial sensors. We then quantified head-pelvis coordination with Joint Recurrence Quantification Analysis, a method sensitive to the coupling between parts of biomechanical systems.

findingsIn people with PD with LID, head-pelvis coupling was higher in the ON medication state than in the OFF medication state. This effect of medication was not observed in people with PD without LID. When OFF medication, people with PD with LID exhibited lower coupling than HC.

interpretationThis is novel evidence that medication and LID interact to alter multisegmental coordination in people with PD, with potential consequences for balance control.