Quantitative Evaluation of Long-Term Parkinson Tremor

Because of wide temporal fluctuations in the severity of Parkinson tremor, long-term observation is required to objectively assess the effects of therapy. This study was conducted to design a system for long-term recording of tremor in the digits or wrist, to examine the stochastic properties of tremor, and to develop a means for temporally compressing the data for rapid clinical interpretation. Forty patients were studied. A telemetry system was used for data acquistion to allow the patients freedom of movement during the recording session. Recording length ranged from ½to 6 h with a mean of 2 h. The data were found to be self-stationary in the wide sense over 1-min epochs. The statistical properties varied with time in individual subjects and there was little uniformity among different subjects. Cross-correlation and cross-spectral density analyses indicated that tremor at corresponding sites in contralateral limbs is relatively independent. Graphs of percent on time, mean frequency, and mean amplitude for contiguous 3-5-min epochs were found most suitable for clinical purposes.