Analysing Motion Capture Kinematics to aid Clinical Assessment and Physiotherapy Strategies in Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP) is a rapidly progressive neurodegenerative disease characterized by postural instability, vertical supranuclear gaze palsy, bradykinesia, extrapyramidal rigidity and dementia. Patients with PSP lose independent gait and ability to stand unassisted, often becoming wheelchair-bound within 1-3 years. Clinically recognized PSP movement features, including tendency to fall backwards, posterior weight distribution and a toe-up maneuver with weight shift to the heels in sit-to-stand transitions, have been used to track progression and consider physiotherapy needs. Quantitative movement analysis of these features may help aid clinical measures of progression, identify high-risk PSP patients and inform falls prevention, chair rise difficulty, and physiotherapy strategies.

Three participants with PSP underwent assessment with the PSP rating scale (PSPRS) and Vicon Nexus motion capture during static standing, dual tasking, external perturbations and sit-to-stand transitions. Exploratory analyses examined center of pressure (CoP), area of sway, ankle joint angles, lateral and anterior-posterior percentage weight distribution and derived time-series measures in correlation with disease severity.

Data showed a strong negative correlation between PSPRS score and average static anterior-posterior mean velocity (r=-1.000, p<0.001), and between PSPRS score and average sit to stand anterior-posterior mean force (r=-1.000, p<0.001). There was a strong positive correlation between PSPRS score and percentage posterior CoP trace during average static standing (r=1.000, p<0.001) and dual tasking (r=1.000, p<0.001). Normalized time-series CoP traces displayed differences in movement parameters over the course of sit-to-stand transitions with severity of disease.

Motion capture quantitative movement analysis captures and adds detail to clinically recognized PSP features, including posterior leaning postural sway, inability to accurately transfer CoP anteriorly-posteriorly, and differences in right and left and posterior weight distribution correlating with PSP disease severity during static standing, sit-to-stand and dual tasking. Our findings also support future investigation of falls prevention and physiotherapy strategies targeting identified kinematics, such as heel inserts.