Abstract
The characteristics of the Parkinson’s disease tremor reported previously are not applicable to the full spectrum of severity. The characteristics of high- and low-amplitude tremors differ in signal regularity and frequency dispersion, a phenomenon that indicates characterisation should be studied separately based on the severity. The subclinical tremor of Parkinson’s disease is close to physiological tremor in terms of amplitude and frequency, and their distinctive features are still undetermined. We aimed to determine joint motion characteristics that are unique to subclinical Parkinson’s disease tremors. The tremors were characterised by four hand–arm motions based on displacement and peak frequencies. The rest and postural tremors of 63 patients with Parkinson’s disease and 62 normal subjects were measured with inertial sensors. The baseline was established from normal tremors, and the joint motions were compared within and between the two subject groups. Displacement analysis showed that pronation–supination and wrist abduction–adduction are the most and least predominant tremor motions for both Parkinson’s disease and normal tremors, respectively. However, the subclinical Parkinson’s disease tremor has significant greater amplitude and peak frequency in specific predominant motions compared with the normal tremor. The flexion–extension of normal postural tremor increases in frequency from the proximal to distal segment, a phenomenon that is explainable by mechanical oscillation. This characteristic is also observed in patients with Parkinson’s disease but with amplification in wrist and elbow joints. The contributed distinctive characteristics of subclinical tremors provide clues on the physiological manifestation that is a result of the neuromuscular mechanism of Parkinson’s disease.
Highlights
The characteristics of the Parkinson’s disease tremor reported previously are not applicable to the full spectrum of severity
The levodopa equivalent dose was derived based on the standardized conversion scale and formulae reported by Tomlinson et al.[12]
The examined tremors had no clinical signs, our analysis revealed the characteristics that are unique to Parkinson’s disease (PD) and normal tremors (Table 1)
Summary
The characteristics of the Parkinson’s disease tremor reported previously are not applicable to the full spectrum of severity. The characteristics of high- and low-amplitude tremors differ in signal regularity and frequency dispersion, a phenomenon that indicates characterisation should be studied separately based on the severity. The flexion–extension of normal postural tremor increases in frequency from the proximal to distal segment, a phenomenon that is explainable by mechanical oscillation This characteristic is observed in patients with Parkinson’s disease but with amplification in wrist and elbow joints. One of the few studies on PD of low and high amplitudes and normal subjects reported the tremor characteristics based on the signal regularity or predictability of the future value in time series. Low-amplitude tremor has a less regular signal Another parameter that has been studied in PD tremors of different severity is the proportion of acceleration power. The difference in the characteristics of high and low amplitudes suggests that PD tremors should be studied at a separate severity level
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