[Direct quantitative measurement of tremor: first results of a new mesuring procedure in patients under lithium therapy].

The use of a new piezoresistive minature accelerometer as part of an electronic measurement system for the direct quantification of human finger tremor in physical units is described. The system was designed to yield digital values for the mean tremor amplitude in a given period of time. Reliability coefficients were computed for a smaple of 34 patients under lithium therapy. Coefficients ranged between 0.75 and 0.94 for test-retest intervals between 30 min and several days. Some of the usual indirect methods for the assessment of tremor showed very low correlations to the true tremor amplitude and seemed to be only of limited usefulness. It was further demonstrated that situational factors play a dominant role independently of the particular method of measurement.