Quantitative assessment of bradykinesia in patients with Parkinson's disease.

In order to optimize a method for quantitative assessment of bradykinesia, we evaluated the three-dimensional sources of a movement signal of the wrist and influence of tremor on the reliability of bradykinesia measurements. A total of 33 patients with Parkinson's disease, three patients with Multiple System Atrophy and 29 healthy controls performed a test procedure to measure slowness of movement, consisting of a tap rate (TR) test and a movement time (MT) test. Simultaneously, accelerometers were mounted on the wrist and mean bi- and tri-axial vectors were calculated. Thus the acquired means of acceleration were correlated with the commonly used measures of bradykinesia. i.e. tap rate and movement time. Our results show that bradykinesia is reliably measured by the evaluation of the mean acceleration of movements, and support the use of any of the three bi-axial vectors. Compared to the bi-axial vectors, the tri-axial vector provided no relevant additional information. Additionally, the presence of a moderate to severe resting tremor did not influence the assessment of bradykinesia. Because of the possibility of continuous assessment of bradykinesia this new monitor may prove to be of great value in pharmacodynamic studies and the longitudinal follow-up of patients in drug trials.