Characteristics Of Tremor Research Articles

Tremor Following Guillain Barré Syndrome.

Neuropathic tremor occurs with damage to the peripheral nervous system. Guillain-Barré syndrome (GBS) causes acute paralysis following nerve inflammation sometimes resulting in long-term disability. It is unclear how frequent and severe tremor is following GBS. We aimed to assess the frequency and features of tremor following GBS. We enrolled 18 patients with GBS treated in a secondary care center within a 4-year period. Evaluations were done with the Fahn-Tolosa-Marin tremor rating scale (FTM-TRS). We compared these features with a cohort of consecutive patients with untreated essential tremor (ET). There were 13 males and 5 females with a mean age at evaluation (S.D.) of 41.5 ± 14.0 years and at GBS onset of 40.2 ± 13.7. No patient had history of tremor before GBS. Upper limb tremor was identified in 16 (89%) cases, 35.5% of patients had FTM-TRS score ≥10 points. Tremor was mostly kinetic, jerky with low amplitude with a total score of 10.94 ± 11.84 in the FTM-TRS. Compared with patients with ET, those with GBS-tremor were younger and had lower scores in all subscales of the FTM-TRS (P value < 0.05 for all comparisons). In a multivariate linear regression analysis "days of hospitalization" had a positive association with the total FTM-TRS score (P = 0.001). Tremor was common following GBS. This tremor is mild compared with patients with ET, but adds functional impact.

Clinical and physiological characteristics of tremor in a large cohort of focal and segmental dystonia

ObjectiveTremor is a frequent co-occurring feature in patients with dystonia, especially in focal and segmental dystonia. Clinical studies have shown that tremor is more commonly observed when dystonia spreads to contiguous body regions. However, there is insufficient characterization of tremor physiology in focal and segmental forms of dystonia. We aimed to ascertain the characteristics of tremor presenting in these specific subtypes.MethodsWe enrolled dystonia patients with head and arm tremors presenting to our center. We categorized these participants as focal and segmental dystonia following the Movement Disorders Society guidelines. We recorded the frequency, amplitude, rhythmicity, burst duration, and discharge pattern on accelerometer and electromyography recordings. We compared the physiology of tremors in focal vs. segmental dystonia. We determined whether the physiology was affected by clinical features such as demographics, age at onset, dystonia duration, alcohol responsiveness, family history, and botulinum toxin responsiveness.Results72 patients, mainly focal cervical dystonia and focal cervical + arm or cranial dystonia (segmental) were enrolled. In the analysis of the head tremor recordings (n = 66; frequency range 3–6.5 Hz), we found that focal vs. segmental dystonia comparisons revealed a significantly lower frequency (mean ± standard deviation; 4.0 ± 0.9 Hz vs. 4.7 ± 1.0 Hz; p = 0.02), lower amplitude (0.004 ± 0.008 g2/Hz vs. 0.006 ± 0.008 g2/Hz; p = 0.03) and longer muscle burst durations (111.1 ± 40.4 ms vs. 91.5 ± 24 ms; p = 0.04). In the analysis of arm tremor recordings (n = 31; frequency range 3.5–7 Hz), we found focal vs. segmental dystonia comparison revealed a lower amplitude (0.04 ± 0.07 g2/Hz vs. 0.06 ± 0.06 g2/Hz; p = 0.045). In the stepwise regression analysis, the age at evaluation (β - 0.44; p = 0.006) and age at onset (β - 0.61; p = 0.005) significantly predicted the head tremor frequency whereas the alcohol responsiveness tended to predict the amplitude of the head tremor (β - 0.5; p = 0.04) and the arm tremor (β - 0.6; p = 0.02).ConclusionOur study found that the physiological characteristics of tremor in focal and segmental dystonia are somewhat distinct, suggesting that the spread of dystonia symptoms from one body region to another may have a bearing on the physiology of co-occurring tremor. The frequency of head tremors in younger participants was observed to be higher compared to older participants. The head and arm tremor tended be less severe in patients reporting alcohol responsiveness.

Impact of SARS-CoV-2 Infection on Essential Tremor: A Retrospective Clinical and Kinematic Analysis.

In the past few years, SARS-CoV-2 infection has substantially impacted public health. Alongside respiratory symptoms, some individuals have reported new neurological manifestations or a worsening of pre-existing neurological conditions. We previously documented two cases of essential tremor (ET) who experienced a deterioration in tremor following SARS-CoV-2 infection. However, the effects of SARS-CoV-2 on ET remain largely unexplored. This study aims to evaluate the impact of SARS-CoV-2 infection on a relatively broad sample of ET patients by retrospectively comparing their clinical and kinematic data collected before and after the exposure to SARS-CoV-2. We surveyed to evaluate the impact of SARS-CoV-2 infection on tremor features in ET. Subsequently, we retrospectively analysed clinical and kinematic data, including accelerometric recordings of postural and kinetic tremor. We included 36 ET patients (14 females with a mean age of 71.1 ± 10.6 years). Among the 25 patients who reported SARS-CoV-2 infection, 11 (44%) noted a subjective worsening of tremor. All patients reporting subjective tremor worsening also exhibited symptoms of long COVID, whereas the prevalence of these symptoms was lower (50%) in those without subjective exacerbation. The retrospective analysis of clinical data revealed a tremor deterioration in infected patients, which was not observed in non-infected patients. Finally, kinematic analysis revealed substantial stability of tremor features in both groups. The study highlighted a potential correlation between the SARS-CoV-2 infection and clinical worsening of ET. Long COVID contributes to a greater impact of tremor on the daily life of ET patients.

Magnetic resonance–guided focused ultrasound thalamotomy for tremor

Magnetic resonance–guided focused ultrasound (MRgFUS) thalamotomy has emerged as an effective treatment for tremor, particularly in those patients who are excluded from deep brain stimulation. The authors illustrate an example of MRgFUS thalamotomy, targeting the ventralis intermedius nucleus, in a 78-year-old patient with tremor who had features of essential tremor and tremor-predominant Parkinson’s disease. Significant tremor improvement was seen during the procedure. The authors review step-by-step the preoperative considerations, Vim targeting, treatment, and outcomes for this evolving treatment modality. The video can be found here: https://stream.cadmore.media/r10.3171/2024.7.FOCVID249

Not All Antihistamines Are Created Equal: Alimemazine As A Cause Of Drug Induced Parkinsonism

Abstract Background A 67year old female presented to a Movement Disorder Service for assessment of tremor. She had a history of presbycusis, dermatitis herpetiformis, bronchiectasis, osteoporosis and stage A chronic lymphocytic leukaemia. History elucidated hypophonia, somniloquy, REM-sleep behaviour disorder, bruxism, presence hallucinosis, insidious bradykinesia and of titubation of increasing prevalence and amplitude over 20years. Examination demonstrated cognitive impairment (Montreal Cognitive Assessment 12+1/30) in the domains of visuospatial function, executive thinking, naming, attention, language, abstraction and anterograde recall. Luria test was 0/6. Also found was: micrographia, left exotropia, reduced left arm and leg swing, kinetic tremor asymmetry, decrement of amplitude and frequency of rapid repetitive movements asymmetrically, mandibular and lingual tremor, positive Kinnier-Wilson test and orthostatic deterioration in yes-yes titubation. Drg history identified use of Alimemazine 10mg for insomnia for approximately 20years. Methods Modified Simpson Angus Scale score was 6 indicating a clinically significant degree of extrapyramidal side effects. Unified Parkinson’s Disease Rating Scale part III was 17. Results Functional dopamine uptake imaging did not indicate a parkinsonian syndrome. Drg induced parkinsonism was diagnosed. 0.0097% of the Northern Ireland population were prescribed Alimemazine in 2022 for non-dermatological reasons, representing 73.49% of all dispensed preparations. In the first financial quarter of 2024 in Northern Ireland, all dispensed prescriptions cost £218,395. Conclusion Not all antihistamines are created equal. Alimemazine is an older phenothiazine derivative antihistamine with central sedative effects equivalent to Chlorpromazine but without anti-adrenaline action. It is rarely prescribed and easily overlooked as “just another antihistamine”. It is commonly prescribed by dermatologists for urticaria. It has substantial pharmacoeconomic implications given its cost disparity with other antihistamines. Extrapyramidal features of tremor, akinesia and hypertonicity are more common in older people; usually developing within weeks or months of commencement. Stopping the drug is the first-line intervention. Resolution of symptoms is not guaranteed.

Radiomics based on diffusion tensor imaging and 3D T1-weighted MRI for essential tremor diagnosis.

Due to the absence of biomarkers, the misdiagnosis of essential tremor (ET) with other tremor diseases and enhanced physiologic tremor is very common in practice. Combined radiomics based on diffusion tensor imaging (DTI) and three-dimensional T1-weighted imaging (3D-T1) with machine learning (ML) give a most promising way to identify essential tremor (ET) at the individual level and further reveal the potential imaging biomarkers. Radiomics features were extracted from 3D-T1 and DTI in 103 ET patients and 103 age-and sex-matched healthy controls (HCs). After data dimensionality reduction and feature selection, five classifiers, including the support vector machine (SVM), random forest (RF), logistic regression (LR), extreme gradient boosting (XGBoost) and multi-layer perceptron (MLP), were adopted to discriminate ET from HCs. The mean values of the area under the curve (mAUC) and accuracy were used to assess the model's performance. Furthermore, a correlation analysis was conducted between the most discriminative features and clinical tremor characteristics. All classifiers achieved good classification performance (with mAUC at 0.987, 0.984, 0.984, 0.988 and 0.981 in the test set, respectively). The most powerful discriminative features mainly located in the cerebella-thalamo-cortical (CTC) and visual pathway. Furthermore, correlation analysis revealed that some radiomics features were significantly related to the clinical tremor characteristics in ET patients. These results demonstrated that combining radiomics with ML algorithms could not only achieve high classification accuracy for identifying ET but also help us to reveal the potential brain microstructure pathogenesis in ET patients.

Action tremor features discovery for essential tremor and Parkinson's disease with explainable multilayer BiLSTM

The tremors of Parkinson's disease (PD) and essential tremor (ET) are known to have overlapping characteristics that make it complicated for clinicians to distinguish them. While deep learning is robust in detecting features unnoticeable to humans, an opaque trained model is impractical in clinical scenarios as coincidental correlations in the training data may be used by the model to make classifications, which may result in misdiagnosis. This work aims to overcome the aforementioned challenge of deep learning models by introducing a multilayer BiLSTM network with explainable AI (XAI) that can better explain tremulous characteristics and quantify the respective discovered important regions in tremor differentiation. The proposed network classifies PD, ET, and normal tremors during drinking actions and derives the contribution from tremor characteristics, (i.e., time, frequency, amplitude, and actions) utilized in the classification task. The analysis shows that the XAI-BiLSTM marks the regions with high tremor amplitude as important in classification, which is verified by a high correlation between relevance distribution and tremor displacement amplitude. The XAI-BiLSTM discovered that the transition phases from arm resting to lifting (during the drinking cycle) is the most important action to classify tremors. Additionally, the XAI-BiLSTM reveals frequency ranges that only contribute to the classification of one tremor class, which may be the potential distinctive feature to overcome the overlapping frequencies problem. By revealing critical timing and frequency patterns unique to PD and ET tremors, this proposed XAI-BiLSTM model enables clinicians to make more informed classifications, potentially reducing misclassification rates and improving treatment outcomes.

Resting-State Network Analysis Reveals Altered Functional Brain Connectivity in Essential Tremor.

Introduction: Essential tremor (ET) comprises motor and non-motor-related features, whereas the current neuro-pathogenetic basis is still insufficient to explain the etiologies of ET. Although cerebellum-associated circuits have been discovered, the large-scale cerebral network connectivity in ET remains unclear. This study aimed to characterize the ET in terms of functional connectivity as well as network. We hypothesized that the resting-state network (RSN) within cerebrum could be altered in patients with ET. Methods: Resting-state functional magnetic resonance imaging (fMRI) was used to evaluate the inter- and intra-network connectivity as well as the functional activity in ET and normal control. Correlation analysis was performed to explore the relationship between RSN metrics and tremor features. Results: Comparison of inter-network connectivity indicated a decreased connectivity between default mode network and ventral attention network in the ET group (p < 0.05). Differences in functional activity (assessed by amplitude of low-frequency fluctuation, ALFF) were found in several brain regions participating in various RSNs (p < 0.05). The ET group generally has higher degree centrality over normal control. Correlation analysis has revealed that tremor features are associated with inter-network connectivity (|r| = 0.135-0.506), ALFF (|r| = 0.313-0.766), and degree centrality (|r| = 0.523-0.710). Conclusion: Alterations in the cerebral network of ET were detected by using resting-state fMRI, demonstrating a potentially useful approach to explore the cerebral alterations in ET.

REM sleep behavior disorder and Prodromal Parkinson’s Disease in patients with Essential Tremor

Several studies suggested the presence of non-motor symptoms in Essential Tremor (ET), including REM sleep behavioral disorder (RBD). RBD is an essential criterion for Prodromal Parkinson's Disease (PPD), suggesting a link between ET and PD. Our objective was to assess the prevalence and features of ET patients with RBD and PDD.RBD was diagnosed by questionnaire screening, followed by polysomnography. PPD risk factors and prodromic markers were assessed with a structured protocol. Patients were characterized regarding tremor features. ET patients with RBD (ET-RBD) and PPD (ET-PPD) were compared to patients without RBD (ET-nonRBD) and without PPD (ET-nonPPD), respectively. ET-RBD patients were also compared with a group of isolated RBD (iRBD) regarding PPD features.We assessed a total of 64 ET patients. Five (8.3 %) and 4 (6.3 %) had criteria for RBD and PPD, respectively. ET-RBD patients did not differ from ET-nonRBD except for a higher prevalence of PPD. There were no significant differences between ET-RBD and iRBD (n = 12) groups. ET-PPD had a higher prevalence of positive DaT-Scans and RBD compared to ET-nonPPD. Three ET-RBD patients had PPD and 3 ET-PPD had RBD.Both RBD and PPD are more frequent in ET patients than in general aged population but not related with specific tremor features. ET-RBD patients did not differ significantly from iRBD patients, a group prone to develop PD. These data suggest a link between ET and PD and are in accordance with studies showing an increase incidence of lewy-body pathology and PD in ET populations.

Comparing Essential Tremor with and without Soft Dystonic Signs and Tremor Combined with Dystonia: The TITAN Study.

Tremor disorders remain as clinical diagnoses and the rate of misdiagnosis between the commonest non-parkinsonian tremors is relatively high. To compare the clinical features of Essential Tremor without other features (pure ET), ET plus soft dystonic signs (ET + DS), and tremor combined with dystonia (TwD). We compared the clinical features of patients with pure ET, ET + DS, and TwD enrolled in The ITAlian tremor Network (TITAN). Linear regression models were performed to determine factors associated with health status and quality of life. Three-hundred-eighty-three patients were included. Sex distribution was significantly different between the groups with males being more represented in pure ET and females in TwD. The initial site of tremor was different between the groups with about 40% of TwD having head tremor and ET + DS unilateral upper limb tremor at onset. This pattern mirrored the distribution of overt dystonia and soft dystonic signs at examination. Sensory trick, task-specificity, and position-dependence were more common, but not exclusive, to TwD. Pure ET patients showed the lowest degree of alcohol responsiveness and ET + DS the highest. Midline tremor was more commonly encountered and more severe in TwD than in the other groups. Regression analyses demonstrated that tremor severity, sex, age, and to a lesser degree the variable "group", independently predicted health status and quality of life, suggesting the existence of other determinants beyond tremor. Pure ET and TwD manifest with a phenotypic overlap, which calls for the identification of diagnostic biomarkers. ET + DS shared features with both syndromes, suggesting intra-group heterogeneity.

Bedside clinical assessment of patients with common upper limb tremor and algorithmic approach.

The diagnostic approach for patients with tremor is challenging due to the complex and overlapping phenotypes among tremor syndromes. The first step in the evaluation of tremor is to identify the tremulous movement and exclude the tremor mimics. The second step is to classify the tremor syndrome based on the characteristics of tremor from historical clues and focused examination (Axis 1). Comprehensive tremor examinations involve the assessment of tremor in different conditions (rest, action or mixed, position or task-specific), distribution of tremor (upper limb, lower limb, head, jaw), positive signs for functional tremor (FT) if suspected (distractibility, entrainment, co-contraction), and associated neurological signs including parkinsonism, dystonic posture, cerebellar/brainstem signs, neuropathy, and cognitive impairment. A pivotal feature in this step is to determine any distinct feature of a specific isolated or combined tremor syndrome. In this review, we propose an algorithm to assess upper limb tremors. Ancillary testing should be performed if clinical evaluation is unclear. The choice of investigation depends on the types of tremors considered to narrow down the spectrum of etiology (Axis 2). Laboratory blood tests are considered for acute onset and acute worsening of tremors, while structural neuroimaging is indicated in unilateral tremors with acute onset, nonclassical presentations, and a combination of neurological symptoms. Neurophysiological study is an important tool that aids in distinguishing between tremor and myoclonus, etiology of tremor and document specific signs of FT. Treatment is mainly symptomatic based depending on the etiology of the tremor and the patient's disabilities.

Propagation and impacts on roadway of mining-induced far-field strong tremors: insights from numerical simulations

Mining-induced far-field mine tremors, which often cause strong ground tremors, are receiving more attention due to their increasing occurrence. Investigating the rock burst risk of roadway caused by those tremors is crucial to ensure production safety. In this study, Variational Mode Decomposition was used to investigate the wave characteristics of strong mine tremors. The propagation and attenuation of these tremors were explored using the dynamic analysis of Flac3d. The amplification factor was introduced to assess the impact of these tremors on roadways. Plastic zone volume increment and Brittle Shear Ratio (BSR) are used to assess the roadway failure and the rock burst potential caused by these tremors, respectively. The main findings are as follows: 1) Compared with the main frequency of near-field mine tremor waveform, the far-field mine tremors waveform are mainly low frequency below 5 Hz; 2) In the simulation, peak vibration velocities of P-wave and S-wave follow a power-law decay as the propagation distance increases, with P-wave attenuating faster than S-wave; 3) Under similar conditions, P-wave induce higher vibration velocities than S-wave, but S-wave generally exhibit a greater amplification factor than P-wave; 4) When the direction of dynamic load is consistent with the direction of maximum principal stress, the rock burst potential of roadway is higher, which explains the phenomenon that the rock burst potential of roadway under S-wave loading is higher than that under P-wave.

Исследование и разработка методов автоматического поиска признаков болезни Паркинсона и эссенциального тремора на базе AUC-диаграмм

Methods and optimization algorithms for automatic search for AUC-diagram-based features of Parkinson's disease and essential tremor were studied and developed. AUC diagrams are a new method for statistical analysis of biomedical signals, based on visualizing the parameters of wave train electrical activity in the brain and muscles. The effectiveness of this method has been demonstrated in solving problems of early and differential diagnosis of Parkinson's disease and essential tremor. The disadvantage of this method is the need to construct and analyze a large number of graphic diagrams. In this regard, automation of the analysis of AUC diagrams is an urgent task. The mathematical problem of finding features based on the analysis of AUC diagrams is reduced to an optimization problem in a multidimensional feature space. A distinctive feature of the space constructed using AUC diagrams is the presence of relatively large compact areas containing local maxima and minima. This property of the feature space facilitates the search for solutions to the optimization problem, but at the same time requires the selection of optimization algorithms and fitness functions that increase the likelihood of detecting global extrema. In this work, methods for automatically searching for global extrema in the multidimensional space of features of wave train electrical activity are investigated and developed.

Unravelling the excitation mechanism of very long-period (VLP) tremors in the Gulf of Guinea: evidence for vibrations of thin surface crustal plates

SUMMARY The Gulf of Guinea exhibits a continuous emission of narrow-band and long-period signals (16, 26 and 27 s) on teleseismic records, yet the underlying excitation mechanism remains unclear. This study establishes a connection between these tremors and the vibration of thin, decoupled crustal plates at unexplored volcanoes in the gulf. We first formulate the damped plate oscillation equation, by incorporating the vibration of the thin surface crustal plate and magma flow in the subsurface sill. The findings reveal that a fundamental-mode vibration with a period of several dozen seconds can be induced by a crustal plate that is less than 1.0 km thick but extends over tens of kilometres in both length and width, given a subsurface sill depth exceeding 10.0 cm. The thin plate hypothesis also allows for excitation of a few overtone modes, but such waves in higher frequencies diminish over long distances, leaving only the monotonous fundamental-mode vibration at teleseismic stations. The long duration of Guinea tremors at each recurrence is attributed to the presence of low viscosity basaltic magma, which influences the damping factor. Direct wave loads at the shallow gulf serve as the primary vibration source, accounting for seasonal variations and recurring patterns. Sporadic energy bursts may also occur due to large storms. Radiation patterns of Guinea tremors are linked to the geometric structure of the thin plate. Our theoretical estimates of tremor spectra closely align with observed data, confirming the model’s accuracy in capturing reported Guinea tremor characteristics. This study provides valuable insights into the origins of very long-period tremors at continental volcanoes.

Persistence of Basal Ganglia Oscillatory Activity During Tremor Attenuation by Movement in Parkinson's Disease Patients.

One of the characteristics of parkinsonian tremor is that its amplitude decreases with movement. Current models suggest an interaction between basal ganglia (BG) and cerebello-thalamo-cortical circuits in parkinsonian tremor pathophysiology. We aimed to correlate central oscillation in the BG with electromyographic activity during re-emergent tremor in order to detect changes in BG oscillatory activity when tremor is attenuated by movement. We performed a prospective, observational study on consecutive parkinsonian patients who underwent deep brain stimulation surgery and presented re-emergent tremor. Coherence analysis between subthalamic nucleus/globus pallidus internus (STN/GPi) tremorous activity measured by microrecording (MER) and electromyogram (EMG) from flexor and extensor wrist muscles during rest, posture, and re-emergent tremor pause was performed during surgery. The statistical significance level of the MER-EMG coherence was determined using surrogate data analysis, and the directionality of information transfer between BG and muscle was performed using entropy transfer analysis. We analyzed 148 MERs with tremor-like activity from 6 patients which were evaluated against the simultaneous EMGs, resulting in 296 correlations. Of these, 26 presented a significant level of coherence at tremor frequency, throughout rest and posture, with a complete EMG stop in between. During the pause, all recordings showed sustained MER peaks at tremor frequency (±1.5 Hz). Information flows preferentially from BG to muscle during rest and posture, with a loss of directionality during the pause. Our results suggest that oscillatory activity in STN/GPi functionally linked to tremor sustains firing frequency during re-emergent tremor pause, thus suggesting no direct role of the BG circuit on tremor attenuation due to voluntary movements. © 2024 International Parkinson and Movement Disorder Society.

Measurement of Functional Brain Network Connectivity in People with Orthostatic Tremor.

Orthostatic tremor is a rare movement disorder characterized by a sensation of unsteadiness and leg tremor while standing. It has been hypothesized that the disorder is attributable to dysregulation of a central oscillatory network in the brain. This putative network includes primary motor cortex, supplementary motor area, cerebellum, thalamus, and pontine tegmentum. We studied this brain network by recording resting-state functional MRI data from individuals with orthostatic tremor. For each participant, we measured resting-state functional connectivity using a seed-based approach. Regions of interest included were components of the putative central oscillatory network and a primary motor thumb region (identified via transcranial magnetic stimulation). A non-central oscillatory network region of interest-posterior cingulate cortex-was included for comparative analysis of a well-characterized intrinsic network, the default mode network. Demographic information, medical history, and tremor characteristics were collected to test associations with functional connectivity. For normative context, data from the 1000 Functional Connectomes Project were analyzed using an identical approach. We observed that tremor and demographic variables were correlated with functional connectivity of central oscillatory network components. Furthermore, relative to healthy comparison participants, patients with orthostatic tremor exhibited qualitatively different patterns of cerebellar resting state functional connectivity. Our study enhances the current understanding of brain network differences related to orthostatic tremor and is consistent with a hypothesized selective decoupling of cerebellum. Additionally, associations observed between functional connectivity and factors including medical history and tremor features may suggest targets for treatment of orthostatic tremor.

Spatiotemporal Characteristics of Tectonic Tremors in the Collisional Orogen of Taiwan

AbstractTaiwan offers a distinctive tectonic setting as a collisional orogen, ideal for studying tectonic tremors and the slow deformation process in the mountain‐building process. Using continuous seismic data at many stations, which have become available recently, and employing the envelope correlation method, we detected ∼7,000 tremor events from 2012 to 2022, with waveform characteristics similar to tectonic tremors worldwide. Beyond the previously known tremor zone beneath the southern Central Range, where newly detected tremors align along a low‐angle thrust plane, we identified several new tremor “hotspots” spanning 200 km along the mountain belt. These hotspots are situated at the termination of the subducting slabs and around the deep (25–50 km) extension of the Central Range fault, where repeating earthquakes occur at a depth of 10–25 km. Our findings suggest a strong linkage between the tremor generation mechanism and the mountain‐building process, potentially influenced by underground fluid and temperature anomalies.

An OpenSim-Based Closed-Loop Biomechanical Wrist Model for Subject-Specific Pathological Tremor Simulation.

A pathological tremor (PT) is an involuntary rhythmic movement of varying frequency and amplitude that affects voluntary motion, thus compromising individuals' independence. A comprehensive model incorporating PT's physiological and biomechanical aspects can enhance our understanding of the disorder and provide valuable insights for therapeutic approaches. This study aims to build a biomechanical model of pathological tremors using OpenSim's realistic musculoskeletal representation of the human wrist with two degrees of freedom. We implemented a Matlab/OpenSim interface for a forward dynamics simulation, which allows for the modeling, simulation, and design of a physiological H∞ closed-loop control. This system replicates pathological tremors similar to those observed in patients when their arm is extended forward, the wrist is pronated, and the hand is subject to gravity forces. The model was individually tuned to five subjects (four Parkinson's disease patients and one diagnosed with essential tremor), each exhibiting distinct tremor characteristics measured by an inertial sensor and surface EMG electrodes. Simulation agreement with the experiments for EMGs, central frequency, joint angles, and angular velocities were evaluated by Jensen-Shannon divergence, histogram centroid error, and histogram intersection. The model emulated individual tremor statistical characteristics, including muscle activations, frequency, variability, and wrist kinematics, with greater accuracy for the four Parkinson's patients than the essential tremor. The proposed model replicated the main statistical features of subject-specific wrist tremor kinematics. Our methodology may facilitate the design of patient-specific rehabilitation devices for tremor suppression, such as neural prostheses and electromechanical orthoses.

Development and Pilot Testing of the Tremor Retrainer Smartphone Application for the Treatment of Functional Tremor.

Functional tremor is a common and disabling condition with limited treatment options. A prior proof-of-concept pilot study sought to translate entrainment, a key diagnostic feature of functional tremor, into a treatment strategy. The Tremor Retrainer smartphone application was developed though a collaboration between neurologists and a software engineer. It analyzes data from smartphone accelerometers to measure baseline tremor frequency, then provides auditory cues at a lower frequency for the patient to match with flexion-extension movements at the wrist. The application provides continuous biofeedback on performance via a visual gauge. Patients with functional tremor underwent a one-week treatment protocol with the Tremor Retrainer application and provided feedback on usability and acceptability to guide software programming. Three pediatric patients completed the one-week protocol and their feedback was used to modify the software. All patients felt that the application was easy to use and could be effective in treating functional tremor. The Tremor Retrainer smartphone application uses auditory cues and a visual gauge to provide a personalized and widely accessible entrainment-based intervention. Pilot testing in pediatric patients provided key feedback for application design. The Tremor Retrainer smartphone application modulates functional tremor frequency by providing pulsed auditory cues for a patient to match with wrist flexion-extension movements while receiving continuous biofeedback via a visual gauge. This adaption of the diagnostic sign of entrainment has potential as an accessible treatment for patients with functional tremor.

Essential Tremor and Essential Tremor Plus Are Essentially Similar Electrophysiologically.

The merits of classifying the heterogeneous group of essential tremors into essential tremor (ET) and essential tremor plus (ETP) are debated. We studied the electrophysiological and spiral characteristics of tremor in ET and ETP. We reviewed standardized videos from a tremor database and clinically classified patients into ET, ETP, or dystonic tremor (DT). The following variables were derived from combined tri-axial accelerometry-surface electromyography (EMG)-peak frequency, total power, peak power, full width half maximum, tremor stability index and EMG-coherence. We analyzed hand-drawn spirals to derive mean deviation, tremor variability, inter-, and intra-loop widths. We compared these variables among the groups. We recruited 72 participants (81.9% male) with mean age 47.7 ± 16.1 years and Fahn-Tolosa-Marin Tremor Rating Scale total score 31.1 ± 14.1. Patients with ET were younger (P = 0.014) and had less severe tremor (P = 0.020) compared to ETP and DT. In ETP group, 48.6% had subtle dystonia. Peak frequency was greater in ETP (7.3 ± 0.3 Hz) compared to DT (6.1 ± 0.4 Hz; P = 0.024). Peak power was greater in ETP and DT for postural tremor. Rest tremor was recordable on accelerometry in 26.7% of ET. Other variables were similar among the groups. Electrophysiological evaluation revealed postural tremor of frequency 6 to 7 Hz in ET, ETP, and DT with subtle differences more severe tremor in ETP and DT, and higher frequency in ETP compared to DT. Our findings suggest a similar tremor oscillator in these conditions, supporting the view that these entities are part of a spectrum of tremor disorders, rather than distinct etiological entities.