Objective: To evaluate unobtrusive motion tracking for objective assessment of bradykinesia of the upper extremity in Parkinson’s disease (PD).

Background: The MDS-UPDRS is the most widely used scale for the assessment of motor function in PD. The scale features repetitive hand movements (e.g., finger tapping and hand opening and closing) to assess bradykinesia. The rating of these tasks is subjective, based on a combination of qualitative movement parameters related to speed, (progressive reduction of) amplitude and interruptions of rhythm. We propose an objective alternative based on markerless, camera-based motion tracking.

Methods: 34 PD patients (22 male; age 65±9 years; H&Y stadia 1-5) performed the finger tapping task and the hand opening and closing task with their most affected hand. Movements of the fingers and hand were recorded for 20s using a camera-based tracking system (Asus XtionPro depth sensor with 3Gear systems software) providing 3D coordinates of estimated joint positions. Parameters related to movement speed (mean absolute velocity, mean maximum velocity), frequency (mean and decrement over time), amplitude (mean and decrement over time) and interruptions of rhythm (number of hesitations) were calculated for each task. Resulting values were compared to 25 control subjects (12 male; age 62±8 years). In addition, associations with the respective items of the MDS-UPDRS were examined.

Results: PD patients performed the finger tapping task with reduced (mean and maximum) velocity, lower frequency, smaller amplitude and more hesitations than healthy subjects. A gradual decrement in frequency, but not amplitude, was observed. Except for amplitude, values were moderately correlated with the MDS-UPDRS score (p<.05). PD patients performed the hand opening and closing task with reduced (mean and maximum) velocity and lower frequency compared to healthy subjects. No differences in amplitude and hesitations could be identified. For velocity and frequency, moderate to strong correlations with the MDS-UPDRS score were observed (p<.05).

Conclusions: Unobtrusive motion tracking offers an alternative for clinical rating scales and may offer easy, objective and quantitative assessment of aspects of bradykinesia in PD patients. It remains to be determined whether this method is superior to clinical assessment in terms of precision, reliability and responsiveness.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/objective-unobtrusive-assessment-of-bradykinesia-in-parkinsons-disease/