Quantification of limb bradykinesia in patients with parkinson's disease using a gyrosensor -improvement and validation

The purpose of this study is to develop a more convenient system for measurement of hand rotation, and to validate the system by correlation of performance indices derived from the system with the bradykinesia score of hand rotation movement during on-medication state. Forty patients with Parkinson's disease and 14 age-matched control subjects participated in this study. The measurement system was developed using a ceramic gyroscope that is significantly smaller and lighter than those in the literature. The sensor signal was bandpass filtered and action tremor was eliminated by additional lowpass filtering (fc=5Hz) with automated tremor discrimination. Four performance indices (RMS velocity and RMS angle, peak power and total power) were derived from the angular velocity signal. Correlations of performance indices with clinical scores and difference of performance indices among subject groups were investigated. Correlations of all performance indices were far better with bradykinesia score of hand rotation (best r=-.78) than with the other categorized subscores of UPDRS (bradykinesia subscore, axial symptom subscore, and total motor score; best r=-.64). Elimination of action tremor resulted in improvement in correlations of RMS velocity and total power with bradykinesia score for hand rotation (r=-.84 from -.81). Differences between low scores were greater in total power and differences between high scores were greater in RMS velocity, suggesting that use of more than one PI would be beneficial for diagnosis of a wide range of patients. The convenient sensor system, action tremor elimination, and performance indices suggested in this study are expected to be useful in clinical situations.