Short-term variability in amplitude and motor topography of whole-body involuntary movements in Parkinsonʹs disease dyskinesias and in Huntingtonʹs chorea

Objectives Clinical observations have noted variability in amplitude of levodopa-induced dyskinesias (LID) in Parkinsonʹs disease (PD) and chorea in Huntingtonʹs disease (HD) during the day. However, no studies have examined whether both the amplitude and body location (motor topography) of whole-body involuntary movement (WBIM) varied over short periods of time (seconds or minutes), which may have a distinct and significant effect on how disruptive these WBIM may be. The present study quantified the variability of WBIM amplitude and motor topography in patients with PD having LID and in patients with HD having chorea. Patients and methods WBIM was quantified using the MotionMonitor™ magnetic motion tracker system. Five patients in each group were tested in two conditions: sitting and standing. Results WBIM increased from sitting to standing, more so in choreic patients. WBIM varied from 17% to 102% of total WBIM amplitude. Chorea tended to present with greater variability than LID in absolute terms in the standing condition, but not when the mean WBIM amplitude was taken into consideration. Motor topography of WBIM also varied more in the HD group, but mostly in the seated condition where more limbs were free to move. Neither group expressed any laterality of involuntary movement, with amplitude being equally distributed on both sides of the body. Conclusion Results show significant short-term variability in amplitude of chorea and LID, as well as, variability in location of these involuntary movements, illustrating the complexity of the adaptations required to live and be active with involuntary movements such as HD chorea or PD dyskinesias.