O-MD003. The complexity of involuntary hand motion distinguishes between essential and parkinsonian tremor

Abstract

Introduction . Essential tremor (ET) and Parkinsonian tremor (PT) are often clinically misdiagnosed. Involuntary hand motion depends upon numerous physiological interactions over multiple temporal-spatial scales. The dynamics of the motion are thus “complex,” and the pathophysiological changes in PT and ET may impact such complexity to different degrees. We hypothesize that measures of complexity may be used to distinguish ET from PT. Methods . Forty-eight participants with clinically-diagnosed PT and 48 age- and sex-matched participants with ET completed this study. Participants performed two 30-second tests within each of the following conditions: sitting while resting arms on chair arms or outstretching arms horizontally. The involuntary motion was derived from accelerometers secured to the dorsum of each hand. The complexity quantified using multiscale entropy and the amplitude and dominant frequency of the motion were calculated. We also confirmed the accuracy of our results using a separate dataset of 22 patients with PT and 22 with ET. Results . Participants with ET had lower complexity of both hands across both conditions (F > 10.8, p0.15, p0.18, p < 0.001) than those with PT, while no significant difference in the amplitude and dominant frequency between groups was observed. Those with lower complexity had longer disease duration (r2 > 0.15, p < 0.009) and greater UPDRS-III scores (r2 > 0.18, p < 0.009). Receiver-operating-characteristic curves revealed that the complexity metric can distinguish ET from PT (resting: AUC = 0.78, cut-off value = 49; postural: AUC = 0.88, cut-off value = 48). Using the cut-off score of 49 in resting condition, it showed an 80% accuracy to identify ET from PT using the complexity metric in resting condition. Using the cut-off score of 48 in postural condition, it revealed a high accuracy of 90% to identify ET from PT. Conclusion . The complexity of involuntary hand motion captures pathophysiological characteristics reflective of PT and ET. This metric may serve as a novel marker to help distinguish ET from PT in clinical practice.