Chanawat Anan

Low-Cost, 3-Dimension, Office-Based Inertial Sensors for Automated Tremor Assessment: Technical Development and Experimental Verification

BACKGROUND Tremors are common clinical complaints among the elderly and non-specialist physicians frequently are challenged by the need to provide an accurate diagnosis of various tremor syndromes, particularly Parkinsons disease and essential tremor in their busy practices. OBJECTIVE We sought to develop an easy-to-use, mobile robust, accurate, and cost-effective instrument that can objectively quantify tremors. METHOD The low-cost, 3-dimension, inertial sensors were developed for automated tremor assessment. The main sensor unit consists of a 3-axis accelerometer and a 3-axis gyroscope for the purpose of measuring the tilting angle relative to the gravity, linear acceleration, and angular velocity of the body segments affected by tremors. The transmitter consists of five main modules, including a microcontroller, power management module, sensor module, external memory interface module, and Bluetooth™ communication interface module, which connects to the sensors by a thin wire. The signal processing utilized fast Fourier transform analysis to include RMS angular rate, RMS angle, RMS rate, RMS velocity, peak frequency, peak frequency magnitude, and dispersion of frequency as variables. RESULT The prototype was tested with a tremor simulator at programmable angular rates of 2-, 4-, and 8-Hz confirming its accuracy. Twenty subjects (10 PD and 10 age-matched ET patients) participated as part of the experimental verification to perform three tremor tasks, including rest, postural, and kinetic tremor according to the teaching videotape of the motor section of the UPDRS. The mean peak frequency was significantly lower in PD than ET patients at rest on the x- (p < 0.01) and z-axis (p < 0.01). In PD patients, the RMS angular rate, RMS angle, RMS rate, RMS velocity, and peak magnitude were all significantly higher than those values in ET patient at rest while the data was not significantly difference during postural and kinetic actions. ET patients had significantly higher peak frequency during postural action in the y-axis than PD patients (p < 0.05). CONCLUSION The study provides the technical development of an accurate, inexpensive, and simple method to measure the kinematics of tremor in humans. Further studies are warranted to confirm the validity of each parameter and the diagnostic accuracy in each tremor syndrome.

Visual deprivation elicits subclinical postural inflexibilities in early Parkinson's disease

BACKGROUND Postural instability is often experienced in the late stages of PD and is a marker of disease progression. Little information is available on the role of visual inputs as an adaptive strategy to compensate for postural instability in PD. The purpose of this study was to determine visual dependency for postural control in early PD. METHODS Thirty early PD subjects without postural complaints and 30 matched controls were evaluated for subtle postural instability using static posturography under eyes opened and eyes closed conditions. RESULTS No significant differences between groups were observed under eyes opened condition. In eyes closed condition, there was significantly greater mean sway in the mediolateral direction (p=0.01), mean sway velocity (p=0.03), lateral sway velocity (p=0.04), and sway area (p=0.04) in PD than in the control subjects. 95% confidence ellipse of mean sway was largest in PD patients with eyes closed. A strong and significant correlation was observed between disease duration and mean mediolateral sway, sway area, mean sway and lateral sway velocity, and a moderate correlation was shown between Hoehn & Yahr stage and mean mediolateral sway, and sway area. CONCLUSION Our findings suggest that visual dependency exists in early PD and visual deprivation task can help identify subclinical postural instability.

Time for a strategy in night-time dopaminergic therapy? An objective sensor-based analysis of nocturnal hypokinesia and sleeping positions in Parkinson's disease

BACKGROUND Nocturnal hypokinesia is a common night-time symptom in patients with Parkinsons disease (PD). However, there is still little understanding of the nature, and variations of severity of this symptom. OBJECTIVES To evaluate the severity of nocturnal hypokinesia and sleep positions in PD patients using multisite wearable sensors. METHODS Nocturnal parameters and sleep positions in 18 PD couples were assessed and compared using wearable sensors (limbs and trunk) for one night in their homes. Nocturnal parameters included number, velocity, acceleration, degree, limb movements and the number of times they got out of bed. RESULTS PD patients had significantly fewer episodes of turns in bed than their spouses (p=0.043), which was associated with significantly slower speed (p=0.005), acceleration (p=0.005) and fewer degrees (p=0.017). When we split the night into the first and second half, significant findings were mainly demonstrated in the second half of the night, including significantly fewer turns (p=0.02) with smaller degrees (p=0.017), slower speed (p=0.005) and acceleration (p=0.007). No significant differences in these parameters were shown in the first half of the night except for smaller degrees of turn in bed in PD patients (p=0.028) and slower acceleration (p=0.037). In addition, PD patients spent significantly more time in a supine position compared to their spouses (p=0.031) with significantly less time in a prone position (p=0.041). CONCLUSION Nocturnal hypokinesia gets worse as the night progresses. Treatment of nocturnal hypokinesia should aim at providing a continuous dopaminergic delivery that can achieve a sustained therapeutic level of dopamine throughout the night.

Support vector machine classification of Parkinson's disease and essential tremor subjects based on temporal fluctuation

Tremor is a common symptom shared in both Parkinsons disease (PD) and Essential tremor (ET) subjects. The differential diagnosis of PD and ET tremor is important since the realization of treatment depends on specific medication. A novel feature is developed based on a hypothesis that tremor of PD subject has a larger fluctuation during resting than action task. Tremor signal is collected using a triaxial gyroscope sensor attached to subjects finger during kinetic and resting task. The angular velocity signal is analyzed by transforming a one-dimensional to two-dimensional signal using a relation of signal and its delay versions. Tremor fluctuation is defined as the area of 95% confidence ellipse covering the two-dimensional signal. The tremor fluctuation during kinetic and resting task is used as classification features. The support vector machine is used as a classifier and tested with 10-fold cross-validation. This novel feature provides a perfect PD/ET classification with 100% accuracy, sensitivity and specificity.

Exploring the effect of electrical muscle stimulation as a novel treatment of intractable tremor in Parkinson's disease

BACKGROUND As the pathophysiology of tremor in Parkinson disease (PD) involves a complex interaction between central and peripheral mechanisms, we propose that modulation of peripheral reflex mechanism by electrical muscle stimulation (EMS) may improve tremor temporarily. OBJECTIVES To determine the efficacy of EMS as a treatment for drug resistant tremor in PD patients. METHODS This study was a single-blinded, quasi-experimental study involving 34 PD patients with classic resting tremor as confirmed by tremor analysis. The EMS was given at 50Hz over the abductor pollicis brevis and interrosseus muscles for 10s with identified tremor parameters before and during stimulation as primary outcomes. RESULTS Compared to before stimulation, we observed a significant reduction in the root mean square (RMS) of the angular velocity (p<0.001) and peak magnitude (p<0.001) of resting tremor while tremor frequency (p=0.126) and dispersion (p=0.284) remained unchanged during stimulation. The UPDRS tremor score decreased from 10.59 (SD=1.74) before stimulation to 8.85 (SD=2.19) during stimulation (p<0.001). The average percentage of improvement of the peak magnitude and RMS angular velocity was 49.57% (SD=38.89) and 43.81% (SD=33.15) respectively. 70.6% and 61.8% of patients experienced at least 30% tremor attenuation as calculated from the peak magnitude and RMS angular velocity respectively. CONCLUSIONS Our study demonstrated the efficacy of EMS in temporarily improving resting tremor in medically intractable PD patients. Although tremor severity decreased, they were not completely eliminated and continued with a similar frequency, thus demonstrating the role of peripheral reflex mechanism in the modulation of tremor, but not as a generator. EMS should be further explored as a possible therapeutic intervention for tremor in PD.

Temporal fluctuation analysis of tremor signal in Parkinson's disease and Essential tremor subjects.

Tremor is a common symptom shared in both Parkinsons disease (PD) and Essential tremor (ET) subjects. The differential diagnosis of PD and ET tremor is important since the treatment depends on specific medication. A novel feature was developed based on a hypothesis stating that the tremor of PD subject has a larger fluctuation while performing resting task than action task. Tremor signal was collected using a gyroscope sensor attached to subjects finger. The angular velocity signal was analyzed by transforming a one-dimensional to two-dimensional signal based on relation of different units of time-delay. The tremor fluctuation was defined as the area of 95% confidence ellipse covering the two-dimensional signal. Experimenting with 32 PD and 20 ET subjects, a ratio of fluctuation of resting to kinetic task can be a sensitive feature to discriminate PD from ET with 100% accuracy.

Tremor assessment using spiral analysis in time-frequency domain

The paper proposed a method for tremor assessment of the Archimedean spiral based on spiral analysis in the time-frequency domain. Spiral analysis is a method of analyzing the drawing of Archimedean spiral to quantify motor activity and evaluate the possible movement disorder symptom such as tremor, an involuntary trembling or shaking movements in one or more parts of the body. One of the most common degenerative disorders of the central nervous system that causes the tremor is Parkinsons disease (PD). It is usually a slowly progressing disease which affects the patient with the following symptoms: tremor, rigidity, slowness of movement, and postural instability. Clinical observation is needed to diagnose the tremor, which requires a trained specialist. Thus, an additional method is desirable to help in the diagnosis process and possibly improve the early detection as well as the measurement of disease severity. Many studies have reported that the spiral analysis may be useful in the diagnosis of motor dysfunction in PD and other movement disorder patients. Moreover, the spiral drawing test can easily be performed using a mobile tablet from anywhere not limited to a hospital. We propose a method for classification of spiral drawing based on spiral analysis in the time-frequency domain. The preliminary result of the selected feature in the time-frequency domain shows that this method could potentially be used to distinguish between movement disorder patient and healthy control.

Tremor's glove-an innovative electrical muscle stimulation therapy for intractable tremor in Parkinson's disease: A randomized sham-controlled trial

BACKGROUND Medically refractory resting tremor is a debilitating symptom of Parkinsons disease (PD) patients. In our pilot study, modulation of peripheral reflex mechanism by electrical muscle stimulation (EMS) temporarily suppressed tremor. OBJECTIVES To investigate the efficacy of EMS, delivered using Tremors glove, as a treatment of resting hand tremor. PATIENTS AND METHODS Thirty PD patients with medically refractory resting tremor were randomly allocated to a Tremors glove group (n=15) or a sham glove group (n=15). Gloves were placed on the most tremulous hand for 30min per testing session. Demographics, clinical rating scales, and tremor parameters (RMS of angular velocity and angular displacement, peak magnitude, and frequency) were assessed before and during stimulation. Correlations with validated clinical rating scales were performed. RESULTS There were no statistically significant differences between groups in demographics, rating scales, or tremor parameters. During stimulation, significant reduction in RMS angular velocity (as percentage) in every axis and peak magnitude in axis (x-, y-) and UPDRS tremor score, were found with Tremors glove compared to the sham groups (p<0.05, each). Significant moderate correlations were observed between a percentage reduction of RMS angular velocity in every axis and UPDRS tremor scores. Mean duration of tremor reduction after stimulation was 107.78±104.15s. No serious adverse events were observed. CONCLUSION In this study, EMS-based Tremors glove was effective in suppressing resting hand tremor in PD patients. Tremors glove is light-weight with a good safety profile, making it a future potential therapeutic option for PD patients with medically refractory tremor.