A Power Spectral Density-Based Method to Detect Tremor and Tremor Intermittency in Movement Disorders

Abstract

There is no objective gold standard to detect tremors. This concerns not only the choice of the algorithm and sensors, but methods are often designed to detect tremors in one specific group of patients during the performance of a specific task. Therefore, the aim of this study is twofold. First, an objective quantitative method to detect tremor windows (TWs) in accelerometer and electromyography recordings is introduced. Second, the tremor stability index (TSI) is determined to indicate the advantage of detecting TWs prior to analysis. Ten Parkinson’s disease (PD) patients, ten essential tremor (ET) patients, and ten healthy controls (HC) performed a resting, postural and movement task. Data was split into 3-s windows, and the power spectral density was calculated for each window. The relative power around the peak frequency with respect to the power in the tremor band was used to classify the windows as either tremor or non-tremor. The method yielded a specificity of 96.45%, sensitivity of 84.84%, and accuracy of 90.80% of tremor detection. During tremors, significant differences were found between groups in all three parameters. The results suggest that the introduced method could be used to determine under which conditions and to which extent undiagnosed patients exhibit tremors.

Smartwatch inertial sensors continuously monitor real-world motor fluctuations in Parkinson’s disease

“…We hypothesized that objective, continuous, and sensitive tracking of tremor and dyskinesia could reveal more granular on-off patterns in a patient's day and serve as a clinical decision support tool to improve medication titration. Previous work has shown that machine learning and kinematics-based algorithms on inertial sensor data can identify Parkinsonian resting tremor and choreiform dyskinesias, a side effect often associated with peak dose of dopamine medications (10,12,13,16,18,34,(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52). However, only a few algorithms have been successfully translated into monitoring systems usable in real-world scenarios and with sufficient patient adherence to potentially affect clinical decision-making (53)(54)(55)(56)(57)(58)(59)(60)(61).…”

Wearable sensors during drawing tasks to measure the severity of essential tremor

“…The 0.5—4 Hz band includes mostly voluntary muscle activity in both unimpaired and tremor-impaired individuals, whereas the 4 -12 Hz band includes physiological and pathological tremor. While tremor frequency tends to be a little greater in physiological tremor, there is substantial overlap with ET frequencies 24 . The chief difference is that pathological tremor usually has more power than physiological tremor, so the relative power at the tremor frequency (or even in the entire tremor band) is greater in tremor-impaired individuals.…”

“…ET shows a frequency between 4 and 12 Hz; its variable amplitude depends on factors such as anxiety, limb position, voluntary activity and disease duration 20 . Clinical measurements may be performed at rest, with the arms held in posture, or with goal-directed or repetitive tasks 20 , 24 . Some sensor systems have significant shortcomings: limited accuracy with prolonged measurement, and a need for axial calibration.…”

Wearable Peripheral Electrical Stimulation Devices for the Reduction of Essential Tremor: A Review

“…Digital systems, such as iPads, have been used to record spiral drawings for analysis and for the potential use of algorithms to increase diagnostic confidence [ 7 ], [ 8 ]. Emerging quantitative measurement systems including accelerometry, electromyography, and sensors and algorithms that synthesize these measurements are being developed and validated [ 9 ]–[ 11 ]. Clinical rating scales and questionnaires tend to be used to evaluate essential tremor in the context of research, for example using the TETRAS scale to assess tremor severity, the QUEST scale to assess tremor-related quality of life or the Bain and Findley Tremor ADL scale to assess the impact of tremor on activities of daily living.…”