Tremor Amplitude Research Articles

Intraoperative Quantification of MDS-UPDRS Tremor Measurements Using 3D Accelerometry: A Pilot Study.

The most frequently used method for evaluating tremor in Parkinson’s disease (PD) is currently the internationally standardized Movement Disorder Society—Unified PD Rating Scale (MDS-UPDRS). However, the MDS-UPDRS is associated with limitations, such as its inherent subjectivity and reliance on experienced raters. Objective motor measurements using accelerometry may overcome the shortcomings of visually scored scales. Therefore, the current study focuses on translating the MDS-UPDRS tremor tests into an objective scoring method using 3D accelerometry. An algorithm to measure and classify tremor according to MDS-UPDRS criteria is proposed. For this study, 28 PD patients undergoing neurosurgical treatment and 26 healthy control subjects were included. Both groups underwent MDS-UPDRS tests to rate tremor severity, while accelerometric measurements were performed at the index fingers. All measurements were performed in an off-medication state. Quantitative measures were calculated from the 3D acceleration data, such as tremor amplitude and area-under-the-curve of power in the 4–6 Hz range. Agreement between MDS-UPDRS tremor scores and objective accelerometric scores was investigated. The trends were consistent with the logarithmic relationship between tremor amplitude and MDS-UPDRS score reported in previous studies. The accelerometric scores showed a substantial concordance (>69.6%) with the MDS-UPDRS ratings. However, accelerometric kinetic tremor measures poorly associated with the given MDS-UPDRS scores (R2 < 0.3), mainly due to the noise between 4 and 6 Hz found in the healthy controls. This study shows that MDS-UDPRS tremor tests can be translated to objective accelerometric measurements. However, discrepancies were found between accelerometric kinetic tremor measures and MDS-UDPRS ratings. This technology has the potential to reduce rater dependency of MDS-UPDRS measurements and allow more objective intraoperative monitoring of tremor.

Seismic tremor reveals slow fracture propagation prior to the 2018 eruption at Sierra Negra volcano, Galápagos

Seismic tremor observed near active volcanoes is an important tool for volcano monitoring as it often appears shortly before eruptions. Although tremor can be generated by a variety of physical processes it is usually interpreted as direct evidence for flowing magma in the sub-surface. These interpretations typically feed into risk assessments for potential eruptions. Using the temporal evolution of tremor amplitude and spectral data from a distributed seismic network that captured the 2018 eruption at Sierra Negra in Galápagos, we determine that tremor is not directly related to sub-surface fluid movement. Instead at Sierra Negra tremor likely indicates a slowly propagating fracture, which is later exploited as a pathway for silent magma flow. Distinct differences in the source migration and the spectral character of pre-eruptive and co-eruptive tremor allow both a location estimate of the future eruption site and a precise timing of the eruption onset.

P 22 Effects of multisensory feedback on tremor severity in essential tremor

Introduction : Essential tremor (ET) amplitude is modulated by visual feedback during target-driven movements: In a grip force task, tremor amplitude increases during large-scale visual feedback compared to low-scale visual feedback. It has not been examined whether visual feedback exclusively modulates action tremor severity or if an increase of other afferent input like auditory information has a modulatory effect on tremor amplitude as well. Also, it is unknown whether the sensory signal itself directly affects the tremor generating network or if the effect is rather indirect: enhanced sensory feedback during targeted driven movements might cause arousal/psychological stress. We hypothesized that (1) amplitude of ET is modulated by variation of auditory feedback in the absence of visual feedback in a force tremor paradigm; (2) increase of tremor amplitude coincides with pupillary dilation as a measure of arousal / psychological stress, independently of the quality of sensory feedback Patients & Methods : 14 ET patients conducted a computer-based experiment in which they were asked to match a target force in a force sensor using their thumb and index finger. The quality of them matching the target force was fed back to the participant visually, auditory or a combination of both. For the visual feedback, 2 bars were displayed on a screen, with the distance between these bars decreasing with approximation of the target force. In auditory feedback, a target tone of 440Hz was asked to match by a second tone which changed pitch when approximating the target force. The amplitude of feedback was manipulated via a scaling factor resulting in a large scale and a small scale feedback condition. To characterize the performance (RMSE to target force) and the tremor severity (Power 4-12 Hz) a 3x2 ANOVA was conducted. To control for arousal / psychological stress-induced via the task, pupillometry was recorded. Results : First results showed a comparable deviation from the target force (RMSE) during the experiment in all three sensory feedback modalities. Additionally, tremor severity did not differ between sensory feedback modalities. The ANOVA revealed an effect of the scaling factor on the tremor severity (Power 4-12Hz) for the visual and also for the auditory feedback condition. Pupillometry consistently showed a significantly increased pupil diameter during the large-scale visual- and auditory feedback conditions compared to the small-scale feedback conditions. Conclusion : Our preliminary findings suggest that action tremor in ET is firstly modulated not only by visual but also auditory feedback in a comparable manner and seems to be modality independent. Secondly, arousal / cognitive stress, as measured here by the pupil size, could mediate the increase of tremor amplitude. Further work is required better understand the role of these two possible mechanisms underlying target-related tremor.

P 57 Markerless, video-based kinematic Tremor Analysis: machine vision in movement disorders

Introduction: Clinimetrics of movement disorders relies on scales such as the Fahn-Tolosa-Marin Tremor Rating Scale for Essential Tremor (ET). However, these rating scales are prone to rater bias. Quantitative measurements of tremor kinematics, which are proxy measures of clinical outcome, can be achieved with gold standard tremor analyses using reflective markers and several special cameras. Due to their resource-intensiveness, broad availability is lacking. We therefore asked whether new developments in the field of machine vision can close the gap between granular clinimetrics and simplicity. Patients & Methods: Using the open-source software DeepLabCut (DLC), we tuned a recurrent convolutional neural network (RCNN) to track anatomic landmarks of the upper body by annotating a total of 1.878 frames from 234 videos of 51 ET patients who had undergone deep brain stimulation for ET and 10 healthy subjects. In a retrospective subcohort of 43 patients, tremor amplitudes were derived using the RCNN predictions. We probed the influence of DBS condition on tremor kinematics and expert annotated tremor rating scores (TRS) using repeated measures (rm-)ANOVA and Wilcoxon signed-ranked tests. Then, we assessed correlation of tremor metrics with TRS. To prospectively validate the method, we calculated the correlation of tremor metrics derived from both the video-based RCNN and the marker-based gold standard approach in 7 patients. The videos for validation were not used for training and were unknown to the network. To test for precision, we assessed relative errors and equivalence of both methods using two one sided T-Tests (TOST). Results: The RCNN achieved a mean Euclidean train/test error of 3.56/10.74 pixels corresponding to the average pixel size of a fingertip. In the retrospective analysis, DBS exerted a significant effect on the mean tremor amplitudes (Friedman test: χ2(3)=45.3, p<.001) and TRS (right: W=7.0, p<.001; left: W=37.5, p<.001). RCNN-derived maximum amplitudes correlated strongly with TRS (right: rs=.789, p<.001; left: rs=.640, p<.001). In the prospective analysis, mean amplitudes derived from both methods were strongly correlated (DBS off: rs=.982, p<.001; DBS on: rs=.824, p<.001). Relative errors of RCNN-derived mean amplitudes from goldstandard measurements did not significantly deviate from zero (p>.06). TOST revealed RCNN-derived measurements to be partially (DBS off: upper bound T(13)=0.5, p=.7; lower bound T(13)=3.9, p<.001) and fully (DBS on: T(13)=-15.2, p<.001; T(13)=14.52, p<.001) located within 90% CI equivalence bounds. Conclusion: We demonstrate the utility of video-based markerless tremor analysis using an RCNN for both retrospective and prospective settings. Our method allows sufficiently accurate measurements of tremor characteristics to assess the severity of the disease and to map individual disease progression.

Phase-locked transcranial electrical brain stimulation for tremor suppression in dystonic tremor syndromes

ObjectiveTo establish the causal role of the cerebellum and motor cortex in dystonic tremor syndromes, and explore the therapeutic efficacy of phase-locked transcranial alternating current stimulation (TACS). MethodsWe applied phase-locked TACS over the ipsilateral cerebellum (N = 14) and contralateral motor cortex (N = 17) in dystonic tremor syndrome patients, while patients assumed a tremor-evoking posture. We measured tremor power using accelerometery during 30 s stimulation periods at 10 different phase-lags (36-degrees increments) between tremor and TACS for each target. Post-hoc, TACS-effects were related to a key clinical feature: the jerkiness (regularity) of tremor. ResultsCerebellar TACS modulated tremor amplitude in a phase-dependent manner, such that tremor amplitude was suppressed or enhanced at opposite sides of the phase-cycle. This effect was specific for patients with non-jerky (sinusoidal) tremor (n = 10), but absent in patients with jerky (irregular) tremor (n = 4). Phase-locked stimulation over the motor cortex did not modulate tremor amplitude. ConclusionsThis study indicates that the cerebellum plays a causal role in the generation of (non-jerky) dystonic tremor syndrome. Our findings suggest pathophysiologic heterogeneity between patients with dystonic tremor syndrome, which mirrors clinical variability. SignificanceWe show tremor phenotype dependent involvement of the cerebellum in dystonic tremor syndrome. Tremor phenotype may thus guide optimal intervention targets.

Smart Sensor Control for Rehabilitation in Parkinson's Patients

Deep brain stimulation (DBS) is a powerful tool to treat the movement disorders created by Parkinson's tremor. The stimulation of one of the two main parts of basal ganglia (BG) in DBS is often provided without the feedback signal of the tremor which leads to undesirable side effects like cognitive impairment, anxiety, and muscle twitches. In this article, two distinct intelligent controllers are designed to stimulate the parts of a non-linear BG including subthalamic nuclei (STN) and globus pallidus internal (GPi) to overcome the current challenges of the DBS. For this purpose, an interval type-2 fractional-order fuzzy proportional derivative plus integrator (IT2FO-FPD+I) is suggested to control the two parts of BG. The control signals of the IT2FO-FPD+I controller are designed based on the tremor values which are measured by a sensor mounted on the patient's finger. Since the quality of output command of IT2FO-FPD+I controller highly depends on its coefficients, these parameters are adjusted by a sine-cosine algorithm-based wavelet mutation, called SCAWM, in a heuristic scheme. The suggested controller delivers both suitable stimulatory control signals to the brain and decreases the amplitude of tremor impressively. Comparative simulation explorations are performed subsequently to ascertain the superior performance of the suggested structured intelligent controller over that of the state-of-the-art methodologies.

Design and Simulation of a Passive Absorber to Reduce Measured Postural Tremor Signal.

Tremor is a semirhythmic oscillatory movement of a body part caused by alternating simultaneous contractions of an antagonistic muscle group. Medical and surgical treatments used to reduce the symptoms of involuntary tremor can cause negative side effects. This study examined the ability of passive vibration absorbers in reducing the amplitude of postural tremor (PT). Inertial measurement unit (IMU) was used to record PT signals at the forearm and hand of a patient. IMU signal was used to excite an upper limb modeled to represent the flexion-extension vibrational motion at the joints. Equations of motion were solved numerically to obtain a response that fits the measured tremor signal. Passive tuned mass damper (TMD) was modeled as a cantilever beam and a screw placed along its length, at a position reflecting its operational frequency. Natural frequency of the TMD was derived for different mass positions and validated numerically and experimentally. Modal damping ratio of the TMD, for each mass position, was also estimated. Mass position and damping coefficient of the TMD were optimized depending on the minimization in the power spectral density (PSD) of angular displacement amplitude at the wrist joint. Optimized three-TMD system of 28.64 g total effective mass with the estimated modal damping ratio reduced 83.1% of the PSD of the angular displacement amplitude. This study showed the performance ability of a lightweight passive absorber in controlling the involuntary tremor of a system excited by the measured tremor signal of a patient.

Aging-associated changes in motor function are ovarian somatic tissue-dependent, but germ cell and estradiol independent in post-reproductive female mice exposed to young ovarian tissue.

A critical mediator of evolution is natural selection, which operates by the divergent reproductive success of individuals and results in conformity of an organism with its environment. Reproductive function has evolved to support germline transmission. In mammalian ovaries, this requires healthy, active gonad function, and follicle development. However, healthy follicles do not contribute to germline transmission in a dead animal. Therefore, support of the health and survival of the organism, in addition to fertility, must be considered as an integral part of reproductive function. Reproductive and chronological aging both impose a burden on health and increase disease rates. Tremors are a common movement disorder and are often correlated with increasing age. Muscle quality is diminished with age and these declines are gender-specific and are influenced by menopause. In the current experiments, we evaluated aging-associated and reproduction-influenced changes in motor function, utilizing changes in tremor amplitude and grip strength. Tremor amplitude was increased with aging in normal female mice. This increase in tremor amplitude was prevented in aged female mice that received ovarian tissue transplants, both in mice that received germ cell-containing or germ cell-depleted ovarian tissue. Grip strength was decreased with aging in normal female mice. This decrease in grip strength was prevented in aged female mice that received either germ cell-containing or germ cell-depleted tissue transplants. As expected, estradiol levels decreased with aging in normal female mice. Estradiol levels did not change with exposure to young ovarian tissues/cells. Surprisingly, estradiol levels were not increased in aged females that received ovaries from actively cycling, young donors. Overall, tremor amplitude and grip strength were negatively influenced by aging and positively influenced by exposure to young ovarian tissues/cells in aged female mice, and this positive influence was independent of ovarian germ cells and estradiol levels. These findings provide a strong incentive for further investigation of the influence of ovarian somatic tissue on health. In addition, changes in tremor amplitude may serve as an additional marker of biological age.

Quantification of Head Tremors in Medical Conditions: A Comparison of Analyses Using a 2D Video Camera and a 3D Wireless Inertial Motion Unit

This study compares two methods to quantify the amplitude and frequency of head movements in patients with head tremor: one based on video-based motion analysis, and the other using a miniature wireless inertial magnetic motion unit (IMMU). Concomitant with the clinical assessment of head tremor severity, head linear displacements in the frontal plane and head angular displacements in three dimensions were obtained simultaneously in forty-nine patients using one video camera and an IMMU in three experimental conditions while sitting (at rest, counting backward, and with arms extended). Head tremor amplitude was quantified along/around each axis, and head tremor frequency was analyzed in the frequency and time-frequency domains. Correlation analysis investigated the association between the clinical severity of head tremor and head linear and angular displacements. Our results showed better sensitivity of the IMMU compared to a 2D video camera to detect changes of tremor amplitude according to examination conditions, and better agreement with clinical measures. The frequency of head tremor calculated from video data in the frequency domain was higher than that obtained using time-frequency analysis and those calculated from the IMMU data. This study provides strong experimental evidence in favor of using an IMMU to quantify the amplitude and time-frequency oscillatory features of head tremor, especially in medical conditions.

Technology efficiency and promotion mechanism on the response output performance of a biomimetic gelatinous polymer actuator based on different process approaches

AbstractIn this paper, from different aspects of internal material composition, biomass modification method and assembly process factor of the biomimetic gelatinous polymer actuator (BGPA), its three process approaches including ionic liquid (IL, [EMIm]BF4) doping amount, sodium alginate (SA) ‐ carboxymethyl chitosan (CMCS) crosslinking ratio and casting assembly temperature were comprehensively compared, and accordingly their technology efficiency and promotion mechanism on response output performance of the BGPA had also been fully researched. The results suggested that under monotonic work cycle, when the IL doping amount was 4 ml, operating life of BGPA reached the maximum of 1720 s and its smallest tremor amplitude was 8.51%. When the SA‐CMCS crosslinking ratio was 5:5, all three evaluation indexes of the duty cycle, internal resistance and elastic modulus of BGPA achieved the minima around 0.97%, 1.61 Ω and 0.207 MPa, respectively. When the casting assembly temperature was 50°C, specific capacitance and output force density of the BGPA separately obtained the largest values of 551.34 mF/g and 16.249 mN/g. Within the cycle repetition period, the best stable output force of the BGPA was approximately 2.877 mN with 4 ml ionic liquid, and its optimal electron current was 12.771 mA at 50°C.

Distractibility predicts favourable response of functional tremor to transcranial magnetic stimulation: An electrophysiological study

BackgroundGeneration of functional tremor relies on the structures involved in the control of voluntary movements. The clinical diagnosis is based on the presence of “positive signs”, which are expression of cognitive and motor distractibility and reflect functional tremor dependence on explicit motor control. In patients who manifest less distractibility, habitual (implicit) control may be of greater significance. Habitual behaviours are inflexible and difficult to eradicate. ObjectivesTo investigate if motor and cognitive distractibility predicts response to treatment with repetitive transcranial magnetic stimulation. Methods21 patients with functional tremor underwent 5-day repeated sessions of continuous theta burst stimulation over primary motor cortex. A battery of tests to provoke positive signs was performed during accelerometry recordings and the total functional tremor accelerometry score was calculated for each patient. Response to treatment was measured as change in tremor amplitude, expressed as total power of the spectra between 1 and 30 Hz. ResultsOn the group level, cTBS significantly changed postural tremor amplitude (Z = −1.9; p = 0.05), with the median decrease of 40%, IQR (−90-(+24)). There was a positive correlation between the functional tremor accelerometry score and reduction of postural tremor amplitude with treatment (rs = −0.75, p < 10−3). Responders had higher functional tremor accelerometry scores compared to non-responders (p = 0.001). The total functional tremor accelerometry score was a significant predictor of treatment response (OR = 2.8, p = 0.03; 95% CI 1.1; 7.2). ConclusionsPatients who are more distractible are better candidates for treatment with transcranial magnetic stimulation. The likely explanation is the between-subjects differences on the reliance of functional tremor generation on explicit vs. implicit motor network.

Analyzing the Effects of Parameters for Tremor Modulation via Phase-Locked Electrical Stimulation on a Peripheral Nerve.

(1) Background: Non-invasive neuromodulation is a promising alternative to medication or deep-brain stimulation treatment for Parkinson’s Disease or essential tremor. In previous work, we developed and tested a wearable system that modulates tremor via the non-invasive, electrical stimulation of peripheral nerves. In this article, we examine the proper range and the effects of various stimulation parameters for phase-locked stimulation. (2) Methods: We recruited nine participants with essential tremor. The subjects performed a bean-transfer task that mimics an eating activity to elicit kinetic tremor while using the wearable stimulation system. We examined the effects of stimulation with a fixed duty cycle, at different stimulation amplitudes and frequencies. The epochs of stimulation were locked to one of four phase positions of ongoing tremor, as measured with an accelerometer. We analyzed stimulation-evoked changes of the frequency and amplitude of tremor. (3) Results: We found that the higher tremor amplitude group experienced a higher rate of tremor power reduction (up to 65%) with a higher amplitude of stimulation when the stimulation was applied at the ±peak of tremor phase. (4) Conclusions: The stimulation parameter can be adjusted to optimize tremor reduction, and this study lays the foundation for future large-scale parameter optimization experiments for personalized peripheral nerve stimulation.

Physiology of Tremor Reduction by Putting the Hands Together in Essential Tremor.

Essential tremor is a common movement disorder, characterized by 4-12 Hz tremor of the hands and arms that can affect many activities of daily living. It has been reported by patients that when performing tasks bimanually their tremor is reduced, but why this happens is unknown. We measured patients' tremors in different conditions when performed with 1 hand and 2 hands to observe if bimanual task performance changes the characteristics of the tremor. A total of 10 patients with essential tremor participated in the study. Electromyographic electrodes were attached bilaterally to the wrist flexor and extensor muscles, and accelerometers were attached to the dorsum of the hands. For each condition, holding a cup, wingbeat, and extending both arms up, data were collected with a single hand and bimanually with the hands touching. When the hands were touching, there was a significant decrease in both accelerometric and electromyographic power at the tremor frequency. In addition, there was a decrease in coherence between accelerometer and electromyography on the same side. There was no change in the tremor frequency. Tremor amplitude does decrease when the hands are together. Together, the characteristics underlying the decrease in tremor amplitude may indicate a decrease in power of the central oscillator driving the tremor, which we speculate is attributed to the differences in unimanual and bimanual motor control. However, given the small sample size, we note that future hypothesis-driven studies with an a priori power analysis will be required to further explore this phenomenon.

The "disease of the crazy hatman" and the effects of human exposure to mercury: A case report / A "doença do homem do chapéu maluco" e os efeitos da exposição humana ao mercúrio: Um relato de caso

INTRODUCTION: Mercury, in addition to being a heavy metal, is considered a neurotoxin, that is, a substance capable of negatively affecting the neurological functions of the human body. Nowadays, ““Mad Hatter's Disease”” is the name used to characterize these neurological disorders caused by mercury. PURPOSE: to report a clinical case of the manifestation of “Mad Hatter's Disease”, as well as to discuss about the effects of human exposure to mercury. METHODOLOGY: this is a clinical case report, in which the patient is essential. CASE REPORT: A 45-year-old male patient, gold miner, from a riverside community in the Amazon, was referred to the hospital with complaints of headache, extremities tremor, diarrhea, tiredness, discouragement, irritability, depression, unusual shyness and hallucinations. On physical examination, the patient was anxious, irritable, symmetrical small-amplitude tremors in the extremities, hyperreflexia ++/4+ in the upper limbs, +/4+ in the lower limbs, normal muscle strength, mild ataxia of the right hand, stained skin and mucous membranes, and acyanotic, with erythematous-scaly lesions, confluent on the trunk, palms and soles of the feet. Screening for mercury poisoning was performed, where it was found, both in blood and urine, the presence of mercury 20 times above the biological tolerance limit. A battery of specific neuropsychological tests was carried out in neurotoxicological assessments and these demonstrated impairment of the cognitive domains (deficit of memory, attention, concentration, reasoning and abstraction) and alterations in motor functions, showing reduced coordination and motor speed. The diagnosis of hydrargyrism or occupational chronic metallic mercuralism (MMCO) was given. DISCUSSION: Chronic occupational exposure to inorganic mercury can cause subclinical abnormalities, as well as long-term psychomotor and neuromuscular behavioral impairment. Neuropsychiatric abnormalities (inattention, memory, interpretation, and motor performance) appear to be dose-related. FINAL CONSIDERATIONS: chronic exposure to metallic mercury vapor characteristically compromises the nervous system, initially with nonspecific symptoms and, later, with characteristic motor disorders - small amplitude tremor, paresis, dysreflexia and difficulty in motor coordination, which gives rise to the "Disease of the Mad Hatter”, and inhaling large amounts of mercury vapor can be lethal.

Cerebello-thalamic activity drives an abnormal motor network into dystonic tremor

Dystonic tremor syndromes are highly burdensome and treatment is often inadequate. This is partly due to poor understanding of the underlying pathophysiology. Several lines of research suggest involvement of the cerebello-thalamo-cortical circuit and the basal ganglia in dystonic tremor syndromes, but their role is unclear. Here we aimed to investigate the contribution of the cerebello-thalamo-cortical circuit and the basal ganglia to the pathophysiology of dystonic tremor syndrome, by directly linking tremor fluctuations to cerebral activity during scanning.In 27 patients with dystonic tremor syndrome (dystonic tremor: n = 23; tremor associated with dystonia: n = 4), we used concurrent accelerometery and functional MRI during a posture holding task that evoked tremor, alternated with rest. Using multiple regression analyses, we separated tremor-related activity from brain activity related to (voluntary) posture holding. Using dynamic causal modelling, we tested for altered effective connectivity between tremor-related brain regions as a function of tremor amplitude fluctuations. Finally, we compared grey matter volume between patients (n = 27) and matched controls (n = 27).We found tremor-related activity in sensorimotor regions of the bilateral cerebellum, contralateral posterior and anterior ventral lateral nuclei of the thalamus (VLp and VLa), contralateral primary motor cortex (hand area), contralateral pallidum, and the bilateral frontal cortex (laterality with respect to the tremor). Grey matter volume was increased in patients compared to controls in the portion of contralateral thalamus also showing tremor-related activity, as well as in bilateral medial and left lateral primary motor cortex, where no tremor-related activity was present. Effective connectivity analyses showed that inter-regional coupling in the cerebello-thalamic pathway, as well as the thalamic self-connection, were strengthened as a function of increasing tremor power.These findings indicate that the pathophysiology of dystonic tremor syndromes involves functional and structural changes in the cerebello-thalamo-cortical circuit and pallidum. Deficient input from the cerebellum towards the thalamo-cortical circuit, together with hypertrophy of the thalamus, may play a key role in the generation of dystonic tremor syndrome.

Detection of Parkinsonian Motor Symptoms Using Non-Invasive Motion Sensing Technology

Parkinson’s Disease (PD) is characterized by impaired movement, resting tremor, and muscle rigidity. The Unified PD Rating Scale (UPDRS) is a standardized protocol used by neurologists to measure progression of disease as well as evaluation of treatments. However, this examination is subjective, time consuming, and results can be affected by stress, diet, or sleep. Our goal is to develop a non-invasive device that can record objective clinically-relevant measurements during subtasks of the UPDRS to allow for remote evaluations, which would be beneficial considering the frequency of clinical visits for medication adjustments. Five healthy individuals (ages 21-59) completed UPDRS tasks 3.6 (pronation/supination of hands) and 3.17 (rest tremor amplitude). Participants performed these tasks twice, first normally and second simulating PD patients (tremor, bradykinesia, reduction of movement amplitude) after viewing example videos. Motion data including linear and angular accelerations in 3 dimensions was acquired using a lightweight wrist-mounted motion sensor. Three features were extracted: (1) Power of higher frequency components of the linear acceleration signal (rest task), as a measure of resting tremor amplitude. (2) Power of higher frequency components of the rotational acceleration signal (pronation/supination task), as a measure of bradykinesia. (3) Standard deviation of the local maxima of the rotational acceleration (pronation/supination task), as a measure of reduction in movement speed and amplitude. These features were used to correctly differentiate trials completed with and without simulated PD symptoms, using an SVM classifier with leave-one-out cross validation accuracy of 95%. These findings suggest it is possible to capture clinical features of PD using motion sensors. Future work in PD patients will examine how these measures correlate with UPDRS evaluations and whether they will be helpful in providing a quick, objective telehealth measure of progression and treatment response that can supplement current tools.

Physiological tremor is suppressed and force steadiness is enhanced with increased availability of serotonin regardless of muscle fatigue.

Although there is evidence that 5-HT acts as an excitatory neuromodulator to enhance maximal force generation, it is largely unknown how 5-HT activity influences the ability to sustain a constant force during steady-state contractions. A total of 22 healthy individuals participated in the study, where elbow flexion force was assessed during brief isometric contractions at 10% maximal voluntary contraction (MVC), 60% MVC, MVC, and during a sustained MVC. The selective serotonin reuptake inhibitor, paroxetine, suppressed physiological tremor and increased force steadiness when performing the isometric contractions. In particular, a main effect of drug was detected for peak power of force within the 8-12 Hz range (P = 0.004) and the coefficient of variation (CV) of force (P < 0.001). A second experiment was performed where intermittent isometric elbow flexions (20% MVC sustained for 2 min) were repeatedly performed so that serotonergic effects on physiological tremor and force steadiness could be assessed during the development of fatigue. Main effects of drug were once again detected for peak power of force in the 8-12 Hz range (P = 0.002) and CV of force (P = 0.003), where paroxetine suppressed physiological tremor and increased force steadiness when the elbow flexors were fatigued. The findings of this study suggest that enhanced availability of 5-HT in humans has a profound influence of maintaining constant force during steady-state contractions. The action of 5-HT appears to suppress fluctuations in force regardless of the fatigue state of the muscle.NEW & NOTEWORTHY Converging lines of research indicate that enhanced serotonin availability increases maximal force generation. However, it is largely unknown how serotonin influences the ability to sustain a constant force. We performed two experiments to assess physiological tremor and force steadiness in unfatigued and fatigued muscle when serotonin availability was enhanced in the central nervous system. Enhanced availability of serotonin reduced physiological tremor amplitude and improved steadiness regardless of muscle fatigue.

Identifying and modulating distinct tremor states through peripheral nerve stimulation in Parkinsonian rest tremor

BackgroundResting tremor is one of the most common symptoms of Parkinson’s disease. Despite its high prevalence, resting tremor may not be as effectively treated with dopaminergic medication as other symptoms, and surgical treatments such as deep brain stimulation, which are effective in reducing tremor, have limited availability. Therefore, there is a clinical need for non-invasive interventions in order to provide tremor relief to a larger number of people with Parkinson’s disease. Here, we explore whether peripheral nerve stimulation can modulate resting tremor, and under what circumstances this might lead to tremor suppression.MethodsWe studied 10 people with Parkinson’s disease and rest tremor, to whom we delivered brief electrical pulses non-invasively to the median nerve of the most tremulous hand. Stimulation was phase-locked to limb acceleration in the axis with the biggest tremor-related excursion.ResultsWe demonstrated that rest tremor in the hand could change from one pattern of oscillation to another in space. Median nerve stimulation was able to significantly reduce (− 36%) and amplify (117%) tremor when delivered at a certain phase. When the peripheral manifestation of tremor spontaneously changed, stimulation timing-dependent change in tremor severity could also alter during phase-locked peripheral nerve stimulation.ConclusionsThese results highlight that phase-locked peripheral nerve stimulation has the potential to reduce tremor. However, there can be multiple independent tremor oscillation patterns even within the same limb. Parameters of peripheral stimulation such as stimulation phase may need to be adjusted continuously in order to sustain systematic suppression of tremor amplitude.

Through the Looking Glass: Remote Versus In-Person Videotaped Neurologic Assessment of Essential Tremor.

Remote assessment of essential tremor (ET) is unverified. To compare assigned tremor scores from a remote videotaped research protocol with those from an in-person videotaped research protocol and assess the validity of remote and in-person videotape-based diagnoses when compared against the intake diagnosis (ET vs. control). Participants with intake diagnoses of ET (11) or controls (15) completed a tremor examination that was filmed both remotely and in person. Agreement between the tremor ratings assigned during remote and in-person videos was substantial (composite κw, 0.67; mean Gwet's AC2 score, 0.92; mean percent agreement, 63.7%). In ET cases with less severe tremor, agreement was lower (p= 0.008). Diagnostic validity was high for both remote and in-person videos compared to the intake diagnosis. Remote video is a reasonable alternative to in-person video for the assessment of tremor severity and assignment of ET diagnoses. However, at low tremor amplitudes, agreement declines.

Triaxial Accelerometry Wireless System for Characterization of Parkinsonian Tremor.

Parkinsonian Tremor (PT) is the most common symptom of Parkinson's disease. Its early detection plays an important role in the diagnosis of the disease as it is often mistaken for another type of tremor, called Essential Tremor (ET). Accelerometry analysis has proven to be a trustworthy method for determining the frequency, amplitude, and occurrence of tremor. In addition, the use of portable and wearable sensors has increased due to the rapid growth of Internet of Things (IoT) technology, allowing data to be collected, processed, stored, and transmitted. In this paper, a wearable system consisting of a digital 3-axis accelerometer ADXL345 and micro-controller unit ESP32 was implemented to transmit accelerometry (ACC) signals from each upper limb simultaneously to a Graphical User Interface (GUI), that was developed in Python as an MQTT client, allowing the user to visualize both real-time and offline signals as well as to add markers to indicate events during the acquisition. Furthermore, this GUI is capable of performing an offline analysis consisting of the computing of Power Spectral Density (PSD) using Welch's method and a Spectrogram to visualize a time-frequency distribution of the ACC signals.