Neurological Tremor: Sensors, Signal Processing and Emerging Applications

Abstract

Neurological tremor is the most common movement disorder, affecting more than 4% of elderly people. Tremor is a non linear and non stationary phenomenon, which is increasingly recognized. The issue of selection of sensors is central in the characterization of tremor. This paper reviews the state-of-the-art instrumentation and methods of signal processing for tremor occurring in humans. We describe the advantages and disadvantages of the most commonly used sensors, as well as the emerging wearable sensors being developed to assess tremor instantaneously. We discuss the current limitations and the future applications such as the integration of tremor sensors in BCIs (brain-computer interfaces) and the need for sensor fusion approaches for wearable solutions.

Assessment of Essential Tremors on Clinical and Functional Performance Tests

“…Assessment of disability done using Activities of Daily Living scales / ADL-T24. 4 Tremor severity was assessed on the basis of difficulties encountered while doing activities of daily living [7]. Tremor severity was divided into mild, moderate, severe, and incapacitating.…”

“…Various rating scales were designed specifically for the assessment of tremor amplitude or the impact of tremor on activities of daily living (ADL) and quality of life [3]. Effect of tremor on daily living activities (ADL) can be evaluated using specific questionnaires such as the ADL-T24, which has a good inter-session reproducibility [4]. The nineHole Peg test and box and block test are simple, low-cost, and efficient test of gross manual dexterity.…”

Quality parameters for a multimodal EEG/EMG/kinematic brain-computer interface (BCI) aiming to suppress neurological tremor in upper limbs

“…The patients were all right-handed and presented with upper limb tremor of grade 1 to 3/4. The ADL-T24 score range was 4–17/24 6 . The Schwab and England ADL score ranged from 50 to 100% 7 .…”

“…Cortical activation occurring during the preparation of movement is detected by the EEG module thanks to a method based on the event-related desynchronization/synchronization (ERD/ERS) phenomenon 6 . By considering: (i) the changes in the β²/α and β/α ratio (representing bursts of β-γ frequencies) during the pre-movement period; (ii) an appropriate threshold indicating which peaks of ratios are actually followed by a movement (and therefore may be considered as a predictor of movement); (iii) the number of movements executed, we extracted a QP for the detection of intentionality of movement 8 .…”

“…Corticomuscular coherence is a function of frequency (with values between 0 and 1) and indicates the degree of correlation between the two signals 10 . The Welch's averaged modified periodogram method was used to compute the magnitude squared coherence of an EEG channel and an EMG electrode along the frequency band 6, 9, 10 . More than 800 possible EEG/EMG combinations (n=832) were tested for the cortico-muscular coherence analysis:…”