Development and Validation of a New Wearable Mobile Device for the Automated Detection of Resting Tremor in Parkinson's Disease and Essential Tremor

Abstract

Involuntary tremor at rest is observed in patients with Parkinson's disease (PD) or essential tremor (ET). Electromyography (EMG) studies have shown that phase displacement between antagonistic muscles at prevalent tremor frequency can accurately differentiate resting tremor in PD from that detected in ET. Currently, phase evaluation is qualitative in most cases. The aim of this study is to develop and validate a new mobile tool for the automated and quantitative characterization of phase displacement (resting tremor pattern) in ambulatory clinical settings. A new low-cost, wearable mobile device, called µEMG, is described, based on low-end instrumentation amplifiers and simple digital signal processing (DSP) capabilities. Measurements of resting tremor characteristics from this new device were compared with standard EMG. A good level of agreement was found in a sample of 21 subjects (14 PD patients with alternating resting tremor pattern and 7 ET patients with synchronous resting tremor pattern). Our results demonstrate that tremor analysis using µEMG is easy to perform and it can be used in routine clinical practice for the automated quantification of resting tremor patterns. Moreover, the measurement process is handy and operator-independent.

Keywords: Parkinson’s disease; electromyography; phase pattern; rest tremor; wearable device.

Figure 1

One second of EMG recording from extensor and flexor muscles of (A) one PD patient and (B) one rET patient. It can be visually assessed that bursts are phase-shifted in (A) and synchronous in (B). EMG: electromyography; PD: Parkinson’s disease; rET: essential tremor with resting tremor.

Figure 2

µEMG experimental system: wearable device and mobile app.

Figure 3

Polar histograms showing phase patterns (phase differences) evaluated with: (A) Dantec Keypoint EMG system; (B) µEMG experimental wearable device. EMG: electromyography.

Figure 4

Comparison of measurements from Dantec Keypoint EMG and µEMG experimental wearable device. Correlation plots for (A) Frequency and (B) phase differences; Bland–Altman plots with 95% confidence interval for (C) Frequency and (D) phase differences. EMG: electromyography.