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Background: Tremor is the most common movement disorder, with significant functional and psychosocial consequences. Oral medications have been disappointing or limited by side effects. Surgical techniques are effective but associated with risks and adverse events. Botulinum toxin (BT) represents a promising avenue but there is still no double-blind evidence of efficacy on upper limb function. A systematic review on the effects of BT in upper-limb tremor was conducted. Methods: A systematic search of the literature was conducted up to July 2023, including the keywords "botulinum toxin" and "tremor". All randomized controlled trials (RCTs) and open-label studies were analyzed. Independent reviewers assessed their methodological quality. Results: There were only eight published RCTs and seven published open-label studies, with relatively small sample sizes. This review suggests that BT is more effective when injections are patient-tailored, with analyses based on clinical judgement or kinematics. Subjective and objective measures frequently improve but transient weakness may occur after injections, especially if wrist or fingers extensors are targeted. A number of studies had methodological limitations. Conclusions: The authors discuss how to optimize tremor assessments and effects of BT injection. Controlled evidence is still lacking but it is suggested that distal "asymmetric" BT injections (targeting flexors/pronators while sparing extensors/supinators) and proximal injections, involving shoulder rotators when indicated, may avoid excessive weakness while optimizing functional benefit. [ABSTRACT FROM AUTHOR]

Background: The clinical differentiation between essential tremor plus (ETP) and dystonic tremor (DT) is challenging. This study aimed at the genetic diagnosis of ETP and DT. Methods: Whole exome sequencing was performed on 50 probands (ETP = 25; DT = 25) and analysed to identify variants in known genes linked with dystonia and essential tremor plus phenotypes. Results: We identified pathogenic/likely pathogenic variants [THAP1 (n = 1) and ANO3 (n = 1)] in two patients with DT. In addition, one DT patient had a variant of uncertain significance in FUS and four patients had benign variants [CIZ1 (n = 1), COL6A3 (n = 1), GCH1 (n = 1), TENM4 (n = 1)]. One patient with ETP was detected to have a variant of uncertain significance in TENM4 and five patients with ETP had benign variants [COL6A3 (n = 2), VPS16 (n = 1), TAF1 (n = 1), KMT2B (n = 1)]. Conclusion: Genetic studies may be in an important biomarker in differentiating patients with ET plus from DT which is challenging in a clinical setting. [ABSTRACT FROM AUTHOR]

Background: Head tremor is common in dystonia syndromes and difficult to treat. Deep brain stimulation (DBS) is a therapeutic option in medically‐refractory cases. In most DBS‐centers, the globus pallidus internus (GPi) is targeted in patients with predominant dystonia and the ventrointermediate nucleus of the thalamus (Vim) in predominant tremor. The aim of the study was to evaluate the effect of GPi‐ versus Vim‐DBS in dystonic or essential head tremor. Methods: All patients with dystonia or essential tremor (ET) (n = 381) who underwent DBS surgery at our institution between 1999 and 2020 were screened for head tremor in our database according to predefined selection criteria. Of the 33 patients meeting inclusion criteria tremor and dystonia severity were assessed at baseline, short‐ (mean 10 months) and long‐term follow‐up (41 months) by two blinded video‐raters. Results: Twenty‐two patients with dystonic head tremor received either GPi‐ (n = 12) or Vim‐stimulation (n = 10), according to the prevailing clinical phenotype. These two groups were compared with 11 patients with ET, treated with Vim‐stimulation. The reduction in head tremor from baseline to short‐ and long‐term follow‐up was 60–70% and did not differ significantly between the three groups. Conclusions: GPi‐DBS effectively and sustainably reduced head tremor in idiopathic dystonia. The effect was comparable to the effect of Vim‐DBS on head tremor in dystonia patients with predominant limb tremor and to the effect of Vim‐DBS on head tremor in ET. [ABSTRACT FROM AUTHOR]

This article discusses a case of Fragile X-associated tremor/ataxia syndrome (FXTAS), a neurodegenerative disorder that affects adults who carry a premutation of the fragile X mental retardation 1 (FMR1) gene. The case study focuses on a 54-year-old man who presented with dystonic tremor as the main symptom. The article highlights the growing evidence that dystonia may be part of the clinical spectrum of FXTAS. The patient's medical history, family history, neurological examination, and diagnostic tests are also discussed. The article emphasizes the need for brain imaging in the diagnosis of FXTAS and suggests that further research is needed to understand the underlying mechanisms of dystonia in this syndrome. [Extracted from the article]

Introduction: This study explores the effects of botulinum neurotoxin (BoNT) on the relationship between dystonia and tremor, specifically focusing on cervical dystonia (CD) and its connection to head tremor. Methods: Fourteen CD patients were recruited; eight (57%) with clinically observable head oscillations were included in further analysis. A highresolution magnetic search coil system precisely measured head movements, addressing two questions: 1) BoNT's effects on head movement amplitude, frequency, and regularity, and 2) BoNT's influence on the relationship between head position and head oscillations. For the first question, temporal head position measurements of three patients were analyzed before and after BoNT injection. The second question examined the effects of BoNT injections on the dependence of the oscillations on the position of the head. Results: Three distinct trends were observed: shifts from regular to irregular oscillations, transitions from irregular to regular oscillations, and an absence of change. Poincaré analysis revealed that BoNT induced changes in regularity, aligning oscillations closer to a consistent "set point" of regularity. BoNT injections reduced head oscillation amplitude, particularly in head orientations linked to high-intensity pre-injection oscillations. Oscillation frequency decreased in most cases, and overall variance in the amplitude of head position decreased post-injection. Discussion: These findings illuminate the complexity of CD but also suggest therapeutic potential for BoNT. They show that co-existing mechanisms contribute to regular and irregular head oscillations in CD, which involve proprioception and central structures like the cerebellum and basal ganglia. These insights advocate for personalized treatment to optimize outcomes that is based on individual head oscillation characteristics. [ABSTRACT FROM AUTHOR]

Objective: Dystonias, characterized by excessive muscle contractions resulting in involuntary postures and movements, impact 3 million people globally, making them the third most common movement disorder. Often accompanied by tremors, dystonias have epidemiological links and non-motor features shared with isolated tremor, such as essential tremor. Both dystonia and tremor present with balance dysfunction and abnormal involuntary movements, potentially linked to abnormal cerebellar function. This study explores the perception of one's own linear movement, heading, particularly discrimination of heading direction, in isolated cervical dystonia, isolated tremor, and their combination. We compare such perception behavior in visual and vestibular domains, predicting that visual heading perception would be superior to vestibular heading perception. Methods: Following the focus on the perception of heading direction, we used psychophysics techniques, such as two-alternative-forced-choice task, to examine perception of direction of one's own movements as they see isolated visual star-cloud movement (visual heading perception) and en bloc body movement (vestibular heading perception). We fitted a sigmoidal psychometric function curve to determine the threshold for visual or vestibular heading perception in our participants. Results: Nineteen participants underwent a two-alternative forced-choice task in the vestibular and visual domains. Results reveal elevated vestibular heading perception thresholds in cervical dystonia with or without tremor, and isolated tremor compared to healthy controls. Vestibular heading perception threshold was comparable in cervical dystonia with tremor and isolated tremor, but it was even worse in isolated cervical dystonia. Visual heading perception, however, remained less affected all three conditions—isolated cervical dystonia, isolated tremor, and their combination. Conclusion: These findings indicate shared deficits and distinctions in the perception of linear translational heading across movement disorders, such as isolated cervical dystonia, tremor, or their combination, offering insights into their pathophysiology, particularly the involvement of cerebellum regions responsible for vestibular processing. [ABSTRACT FROM AUTHOR]

Background: Five cases of tremor only upon smiling have been reported where no facial tremor is present at rest, when talking, or with full smile. Cases: This report highlights four cases of tremor upon partial smiling, discusses the phenomenology of smiling tremor, and reviews the current literature. Four subjects with lower facial tremor present only upon smiling underwent movement disorders evaluation with video. Tremor frequencies were determined by parsing the video clips into 1‐second intervals and averaging the number of oscillations per interval and were determined to be high‐frequency 8 to 10 Hz irregular facial tremors with harmonic variations upon moderate effort in all cases. Slight or full‐effort smiling did not elicit facial muscle oscillations. Subjects had no other signs of tremor, dystonia, or parkinsonism on examination or in family history. Conclusions: Tremor upon smiling only, or isolated smiling tremor, is a unique task‐ and position‐specific tremor of the facial musculature. [ABSTRACT FROM AUTHOR]

BackgroundThe clinical differentiation between essential tremor plus (ETP) and dystonic tremor (DT) is challenging. This study aimed at the genetic diagnosis of ETP and DT.MethodsWhole exome sequencing was performed on 50 probands (ETP = 25; DT = 25) and analysed to identify variants in known genes linked with dystonia and essential tremor plus phenotypes.ResultsWe identified pathogenic/likely pathogenic variants [THAP1 (n = 1) and ANO3 (n = 1)] in two patients with DT. In addition, one DT patient had a variant of uncertain significance in FUS and four patients had benign variants [CIZ1 (n = 1), COL6A3 (n = 1), GCH1 (n = 1), TENM4 (n = 1)]. One patient with ETP was detected to have a variant of uncertain significance in TENM4 and five patients with ETP had benign variants [COL6A3 (n = 2), VPS16 (n = 1), TAF1 (n = 1), KMT2B (n = 1)].ConclusionGenetic studies may be in an important biomarker in differentiating patients with ET plus from DT which is challenging in a clinical setting.

IntroductionBradykinesia is an essential diagnostic criterion for Parkinson’s disease (PD) but is frequently observed in many non-parkinsonian movement disorders, complicating differential diagnosis, particularly in disorders featuring tremors. The presence of bradykinetic features in the subset of dystonic tremors (DT), either “pure” dystonic tremors or tremors associated with dystonia, remains currently unexplored. The aim of the current study was to evaluate upper limb bradykinesia in DT patients, comparing them with healthy controls (HC) and patients with PD by observing repetitive finger tapping (FT).MethodsThe protocol consisted of two main parts. Initially, the kinematic recording of repetitive FT was performed using optical hand tracking system (Leap Motion Controller). The values of amplitude, amplitude decrement, frequency, frequency decrement, speed, acceleration and number of halts of FT were calculated. Subsequently, three independent movement disorder specialists from different movement disorders centres, blinded to the diagnosis, rated the presence of FT bradykinesia based on video recordings.ResultsThirty-six subjects participated in the study (12 DT, 12 HC and 12 early-stage PD). Kinematic analysis revealed no significant difference in the selected parameters of FT bradykinesia between DT patients and HC. In comparisons between DT and PD patients, PD patients exhibited bigger amplitude decrement and slower FT performance. In the blinded clinical assessment, bradykinesia was rated, on average, as being present in 41.6% of DT patients, 27.7% of HC, and 91.7% of PD patients. While overall inter-rater agreement was moderate, weak agreement was noted within the DT group.DiscussionClinical ratings indicated signs of bradykinesia in almost half of DT patients. The objective kinematic analysis confirmed comparable parameters between DT and HC individuals, with more pronounced abnormalities in PD across various kinematic parameters. Interpretation of bradykinesia signs in tremor patients with DT should be approached cautiously and objective motion analysis might complement the diagnostic process and serve as a decision support system in the choice of clinical entities.

Background: Tremor is the most common movement disorder, with significant functional and psychosocial consequences. Oral medications have been disappointing or limited by side effects. Surgical techniques are effective but associated with risks and adverse events. Botulinum toxin (BT) represents a promising avenue but there is still no double-blind evidence of efficacy on upper limb function. A systematic review on the effects of BT in upper-limb tremor was conducted. Methods: A systematic search of the literature was conducted up to July 2023, including the keywords “botulinum toxin” and “tremor”. All randomized controlled trials (RCTs) and open-label studies were analyzed. Independent reviewers assessed their methodological quality. Results: There were only eight published RCTs and seven published open-label studies, with relatively small sample sizes. This review suggests that BT is more effective when injections are patient-tailored, with analyses based on clinical judgement or kinematics. Subjective and objective measures frequently improve but transient weakness may occur after injections, especially if wrist or fingers extensors are targeted. A number of studies had methodological limitations. Conclusions: The authors discuss how to optimize tremor assessments and effects of BT injection. Controlled evidence is still lacking but it is suggested that distal “asymmetric” BT injections (targeting flexors/pronators while sparing extensors/supinators) and proximal injections, involving shoulder rotators when indicated, may avoid excessive weakness while optimizing functional benefit.

Background: The current literature comparing outcomes after a unilateral magnetic resonance image–guided focused ultrasound (MRgFUS) thalamotomy between tremor syndromes is limited and remains a possible preoperative factor that could help predict the long‐term outcomes. Objective: The aim was to report on the outcomes between different tremor syndromes after a unilateral MRgFUS thalamotomy. Methods: A total of 66 patients underwent a unilateral MRgFUS thalamotomy for tremor between November 2018 and May 2020 at St Vincent's Hospital Sydney. Each patient's tremor syndrome was classified prior to treatment. Clinical assessments, including the hand tremor score (HTS) and Quality of Life in Essential Tremor Questionnaire (QUEST), were performed at baseline and predefined intervals to 36 months. Results: A total of 63 patients, comprising 30 essential tremor (ET), 24 dystonic tremor (DT), and 9 Parkinson's disease tremor (PDT) patients, returned for at least one follow‐up. In the ET patients, at 24 months there was a 61% improvement in HTS and 50% improvement in QUEST compared to baseline. This is in comparison to PDT patients, where an initial benefit in HTS and QUEST was observed, which waned at each follow‐up, remaining significant only up until 12 months. In the DT patients, similar results were observed to the ET patients: at 24 months there was a 61% improvement in HTS and 43% improvement in QUEST compared to baseline. Conclusion: These results support the use of unilateral MRgFUS thalamotomy for the treatment of DT, which appears to have a similar expected outcome to patients diagnosed with ET. Patients with PDT should be warned that there is a risk of treatment failure. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance‐guided focused ultrasound (MRgFUS) thalamotomy is increasingly used to treat drug‐resistant essential tremor (ET). Data on MRgFUS thalamotomy in dystonic tremor (DT) are anecdotal. Objectives: To investigate efficacy, safety, and differences in target coordinates of MRgFUS thalamotomy in DT versus ET. Methods: Ten patients with DT and 35 with ET who consecutively underwent MRgFUS thalamotomy were followed for 12 months. Although in both groups the initial surgical planning coordinates corresponded to the ventralis intermediate (Vim), the final target could be modified intraoperatively based on clinical response. Results: Tremor significantly improved in both groups. The thalamic lesion was significantly more anterior in DT than ET. Considering both ET and DT groups, the more anterior the lesion, the lower the odds ratio for adverse events. Conclusions: MRgFUS thalamotomy is safe and effective in DT and ET. Compared to classical Vim coordinates used for ET, more anterior targeting should be considered for DT. [ABSTRACT FROM AUTHOR]

Introduction: This study explores the effects of botulinum neurotoxin (BoNT) on the relationship between dystonia and tremor, specifically focusing on cervical dystonia (CD) and its connection to head tremor.Methods: Fourteen CD patients were recruited; eight (57%) with clinically observable head oscillations were included in further analysis. A high-resolution magnetic search coil system precisely measured head movements, addressing two questions: 1) BoNT’s effects on head movement amplitude, frequency, and regularity, and 2) BoNT’s influence on the relationship between head position and head oscillations. For the first question, temporal head position measurements of three patients were analyzed before and after BoNT injection. The second question examined the effects of BoNT injections on the dependence of the oscillations on the position of the head.Results: Three distinct trends were observed: shifts from regular to irregular oscillations, transitions from irregular to regular oscillations, and an absence of change. Poincaré analysis revealed that BoNT induced changes in regularity, aligning oscillations closer to a consistent “set point” of regularity. BoNT injections reduced head oscillation amplitude, particularly in head orientations linked to high-intensity pre-injection oscillations. Oscillation frequency decreased in most cases, and overall variance in the amplitude of head position decreased post-injection.Discussion: These findings illuminate the complexity of CD but also suggest therapeutic potential for BoNT. They show that co-existing mechanisms contribute to regular and irregular head oscillations in CD, which involve proprioception and central structures like the cerebellum and basal ganglia. These insights advocate for personalized treatment to optimize outcomes that is based on individual head oscillation characteristics.

Background: Thalamic deep brain stimulation (DBS) is established for medically refractory tremor syndromes and globus pallidus stimulation (GPi‐DBS) for medically refractory dystonia syndromes. For combined tremor and dystonia syndromes, the best target is unclear. Objectives: We present four patients with two different profiles whose clinical course demonstrates that our current analysis of clinical symptomatology is not a sufficient predictor of surgical success. Methods: Outcome parameters were assessed with observer‐blinded video ratings and included the Fahn‐Tolosa‐Marin‐Tremor Rating Scale (FTM‐TRS) and the Unified Dystonia Rating Scale (UDRS). Results: Two patients with "predominant lateralized action tremor" of the hands and mild cervical dystonia showed no relevant tremor improvement after GPi‐DBS, but UDRS improved (mean, 45%). Rescue ventral intermediate nucleus of the thalamus (Vim)‐DBS electrodes were implanted and both patients benefited significantly with a mean tremor reduction of 51%. Two other patients with "axial‐predominant action tremor of the trunk and head" associated with cervical dystonia underwent bilateral Vim‐DBS implantation with little effect on tremor (24% reduction in mean FTM‐TRS total score) and no effect on dystonic symptoms. GPi rescue DBS was implanted and showed a significant effect on tremor (63% reduction in mean FTM‐TRS) and dystonia (49% reduction in UDRS). Conclusions: The diagnosis of dystonic tremor alone is not a sufficient predictor to establish the differential indication of GPi‐ or Vim‐DBS. Further criteria (eg, proximal‐distal distribution of tremor/dystonia) are needed to avoid rescue surgery in the future. On the other hand, the course of our patients encourages rescue surgery in such severely disabled patients if the first target fails. [ABSTRACT FROM AUTHOR]

Background: Neuropathic Tremor (NT) is a postural/kinetic tremor of the upper extremity, often encountered in patients with chronic neuropathies such as paraprotein‐associated and hereditary neuropathies. Objectives: To describe the clinical and electrophysiological features of NT in a previously underrecognized setting‐ during recovery from Guillain‐Barré Syndrome (GBS). Methods: Patients with a documented diagnosis of GBS in the past, presenting with tremor were identified from review of clinical records. Participants underwent structured, videotaped neurological examination, and electrophysiological analysis using tri‐axial accelerometry‐surface electromyography. Tremor severity was assessed using the Fahn‐Tolosa‐Marin Tremor Rating Scale. Results: We describe the clinical and electrophysiological features of 5 patients with GBS associated NT. Our cohort had a fine, fast, and slightly jerky postural tremor of frequency ranging from 8 to 10 Hz. Dystonic posturing and overflow movements were noted in 4/5 patients. Tremor appeared 3 months–5 years after the onset of GBS, when patients had regained near normal muscle strength and deep tendon jerks were well elicitable. Electrophysiological analysis of tremor strongly suggested the presence of a central oscillator in all patients. Conclusion: NT is not limited to chronic inflammatory or hereditary neuropathies and may occur in the recovery phase of GBS. The tremor is characterized by a high frequency, jerky postural tremor with dystonic posturing. Electrophysiological evaluation suggests the presence of a central oscillator, hypothetically the cerebellum driven by impaired sensorimotor feedback. [ABSTRACT FROM AUTHOR]

Background: Previous studies have found gait and balance abnormalities in patients with cervical dystonia. However, the characteristics of gait and balance in cervical dystonia with head tremors have not been ascertained. A midline constant head tremor when walking would likely render gait and balance more difficult. The pathophysiology of dystonia has also been increasingly linked with cerebellar function abnormality, commonly implicated in gait and balance disorders. Methods: We examined the gait and balance characteristics of cervical dystonia presentingwith head tremors. We used the timed up-and-go (TUG)walk test, 10m walk test, Berg Balance Scale (BBS), and Gait and Freezing questionnaire. We then assessed the gait on an instrumented walkway system to capture spatiotemporal measures such as speed, cadence, step time, step length, stride width, swing%, stance%, single support%, double support%, and gait variability index (GVI). We also assessed whether the gait in dystonic tremor (DT) differed from essential tremor (ET) and orthostatic tremor (OT), as these tremor disorders share the cerebellothalamo-cortical pathway as the common pathological pathway. Results: 50 participants comprising DT (20 patients), ET (15 patients), and OT (15 patients) were enrolled. While the gait abnormalities were subclinical, 11/20 DT patients (55%) walked at a slower speed on the TUG, 11/20 (55%) had reduced scores on the BBS, 9/20 (45%) had increased step time, 4/20 (20%) had reduced step length, 4/20 (20%) hadwider stride width, 9/20 (45%) spent greater time during double support and 8/20 (40%) patients had an abnormal GVI. Comparisons of DT with healthy control data revealed a slower gait velocity (p = 0.001) and a reduced step length (p = 0.001). Compared to DT, the ET group revealed a reduced cadence (p = 0.04) and the OT group revealed an increased TUG time (p = 0.03), reduced BBS scores (p = 0.02), reduced step length (p = 0.02), reduced cadence (p=0.03), reduced GVI (p = 0.01), and increased double support phase (p = 0.045). Conclusion: DT is accompanied by multiple abnormalities affecting gait and balance, albeit subclinical and less pronounced than ET and OT, possibly related to more effective compensatory mechanisms. Nevertheless, these abnormalities indicate that rehabilitative measures warrant consideration when managing in clinical settings. [ABSTRACT FROM AUTHOR]

Keywords: tremor; dystonic tremor; stroke; lesion EN tremor dystonic tremor stroke lesion 1203 1206 4 08/29/23 20230801 NES 230801 Dystonic tremor is defined by the occurrence of tremor and dystonia in the same body part.[1] Dystonia secondary to stroke is a well-known phenomenon,[2] however the disappearance of dystonia or dystonic tremor after stroke has not been reported.[3] We present a patient with dystonic tremor, which was abolished on the right side after contralateral stroke in the posterior limb of the internal capsule. Brain magnetic resonance imaging (MRI) showed no lesions in the basal ganglia and cerebellum (Fig. Lesion quantification toolkit: a MATLAB software tool for estimating grey matter damage and white matter disconnections in patients with focal brain lesions. [Extracted from the article]

Objective: Dystonias, characterized by excessive muscle contractions resulting in involuntary postures and movements, impact 3 million people globally, making them the third most common movement disorder. Often accompanied by tremors, dystonias have epidemiological links and non-motor features shared with isolated tremor, such as essential tremor. Both dystonia and tremor present with balance dysfunction and abnormal involuntary movements, potentially linked to abnormal cerebellar function. This study explores the perception of one’s own linear movement, heading, particularly discrimination of heading direction, in isolated cervical dystonia, isolated tremor, and their combination. We compare such perception behavior in visual and vestibular domains, predicting that visual heading perception would be superior to vestibular heading perception. Methods: Following the focus on the perception of heading direction, we used psychophysics techniques, such as two-alternative-forced-choice task, to examine perception of direction of one’s own movements as they see isolated visual star-cloud movement (visual heading perception) and en bloc body movement (vestibular heading perception). We fitted a sigmoidal psychometric function curve to determine the threshold for visual or vestibular heading perception in our participants. Results: Nineteen participants underwent a two-alternative forced-choice task in the vestibular and visual domains. Results reveal elevated vestibular heading perception thresholds in cervical dystonia with or without tremor, and isolated tremor compared to healthy controls. Vestibular heading perception threshold was comparable in cervical dystonia with tremor and isolated tremor, but it was even worse in isolated cervical dystonia. Visual heading perception, however, remained less affected all three conditions—isolated cervical dystonia, isolated tremor, and their combination. Conclusion: These findings indicate shared deficits and distinctions in the perception of linear translational heading across movement disorders, such as isolated cervical dystonia, tremor, or their combination, offering insights into their pathophysiology, particularly the involvement of cerebellum regions responsible for vestibular processing.

Background: Previous studies have found gait and balance abnormalities in patients with cervical dystonia. However, the characteristics of gait and balance in cervical dystonia with head tremors have not been ascertained. A midline constant head tremor when walking would likely render gait and balance more difficult. The pathophysiology of dystonia has also been increasingly linked with cerebellar function abnormality, commonly implicated in gait and balance disorders.Methods: We examined the gait and balance characteristics of cervical dystonia presenting with head tremors. We used the timed up-and-go (TUG) walk test, 10 m walk test, Berg Balance Scale (BBS), and Gait and Freezing questionnaire. We then assessed the gait on an instrumented walkway system to capture spatiotemporal measures such as speed, cadence, step time, step length, stride width, swing%, stance%, single support%, double support%, and gait variability index (GVI). We also assessed whether the gait in dystonic tremor (DT) differed from essential tremor (ET) and orthostatic tremor (OT), as these tremor disorders share the cerebello-thalamo-cortical pathway as the common pathological pathway.Results: 50 participants comprising DT (20 patients), ET (15 patients), and OT (15 patients) were enrolled. While the gait abnormalities were subclinical, 11/20 DT patients (55%) walked at a slower speed on the TUG, 11/20 (55%) had reduced scores on the BBS, 9/20 (45%) had increased step time, 4/20 (20%) had reduced step length, 4/20 (20%) had wider stride width, 9/20 (45%) spent greater time during double support and 8/20 (40%) patients had an abnormal GVI. Comparisons of DT with healthy control data revealed a slower gait velocity (p = 0.001) and a reduced step length (p = 0.001). Compared to DT, the ET group revealed a reduced cadence (p = 0.04) and the OT group revealed an increased TUG time (p = 0.03), reduced BBS scores (p = 0.02), reduced step length (p = 0.02), reduced cadence (p = 0.03), reduced GVI (p = 0.01), and increased double support phase (p = 0.045).Conclusion: DT is accompanied by multiple abnormalities affecting gait and balance, albeit subclinical and less pronounced than ET and OT, possibly related to more effective compensatory mechanisms. Nevertheless, these abnormalities indicate that rehabilitative measures warrant consideration when managing in clinical settings.

Objective: To develop an automated algorithm to detect, quantify, and differentiate between tremor using pen-on-paper spirals. Methods: Patients with essential tremor (n = 25), dystonic tremor (n = 25), Parkinson’s disease (n = 25), and healthy volunteers (HV, n = 25) drew free-hand spirals. The algorithm derived the mean deviation (MD) and tremor variability from scanned images. MD and tremor variability were compared with 1) the Bain and Findley scale, 2) the Fahn–Tolosa–Marin tremor rating scale (FTM–TRS), and 3) the peak power and total power of the accelerometer spectra. Inter and intra loop widths were computed to differentiate between the tremor. Results: MD was higher in the tremor group (48.9 ± 26.3) than in HV (26.4 ± 5.3; p < 0.001). The cut-off value of 30.3 had 80.9% sensitivity and 76.0% specificity for the detection of the tremor [area under the curve: 0.83; 95% confidence index (CI): 0.75, 0.91, p < 0.001]. MD correlated with the Bain and Findley ratings (rho = 0.491, p = 0 < 0.001), FTM–TRS part B (rho = 0.260, p = 0.032) and accelerometric measures of postural tremor (total power, rho = 0.366, p < 0.001; peak power, rho = 0.402, p < 0.001). Minimum Detectable Change was 19.9%. Inter loop width distinguished Parkinson’s disease spirals from dystonic tremor (p < 0.001, 95% CI: 54.6, 211.1), essential tremor (p = 0.003, 95% CI: 28.5, 184.9), or HV (p = 0.036, 95% CI: -160.4, -3.9). Conclusion: The automated analysis of pen-on-paper spirals generated robust variables to quantify the tremor and putative variables to distinguish them from each other. Significance: This technique maybe useful for epidemiological surveys and follow-up studies on tremor.

Tremor is part of the phenomenological spectrum of dystonia. Treatments available for tremor in dystonia are oral medications (OM), botulinum neurotoxin (BoNT), and brain surgery (deep brain stimulation or thalamotomy). There is limited knowledge regarding the outcome of different treatment options, and evidence is especially scarce for the tremor of the upper limbs occurring in people with dystonia. In this single-center retrospective study, we evaluated the outcome of different treatments in a cohort of people with upper limb dystonic tremors. Demographic, clinical, and treatment data were analyzed. Dropout rates and side effects were specifically assessed, as well as the 7-point patient-completed clinical global impression scale (p-CGI-S, 1: very much improved; 7: very much worse) as outcome measures. A total of 47 subjects (46.8% female) with dystonic tremor, tremor associated with dystonia, or task-specific tremor were included, with a median age at onset of 58 years (7–86). A total of 31 subjects were treated with OM, 31 with BoNT, and 7 with surgery. Dropout rates with OM were 74.2% due to either lack of efficacy (n = 10) or side effects (n = 13). A total of 7 patients treated with BoNT (22.6%) had mild weakness, causing dropout in 2. P-CGI-S was ≤3 (improvement) in 39% with OM, compared to 92% with BoNT and 100% with surgery. These findings suggest good symptom control of the tremor of the upper limb in dystonia with BoNT and surgery, with higher rates of dropout and side effects with OM. Randomized controlled studies are needed to confirm our findings and provide further insight into better selecting suitable patients for BoNT or brain surgery. [ABSTRACT FROM AUTHOR]

Next generation sequencing gene panel for movement disorders identified in the proband a de novo heterozygous c.1108delG variant in exon 8 of the I CACNA1A i gene (NM 001127222.2), causing a premature stop codon (p.Val370TrpTer7). Keywords: dystonic tremor; tremor; children; CACNA1A EN dystonic tremor tremor children CACNA1A 1554 1556 3 10/24/23 20231001 NES 231001 Pathogenic variants in the I CACNA1A i gene have been associated to a wide spectrum of neurological disorders including paroxysmal and persistent epileptic or non-epileptic symptoms.[1] Cerebellar phenotype is a relevant clinical features including autosomal-dominant spinocerebellar ataxias, several autosomal recessive ataxias and episodic ataxias.[2] Herein we describe a Caucasian 14-year-old female, fourth child of non-consanguineous healthy parents, born at term via scheduled caesarean section. Dystonia have been recently reported associated to I CACNA1A i by two independent group showing activity-induced dystonia[3] and cervical dystonia[4] with mild ataxia. [Extracted from the article]

The article titled "Defining 'Dystonic Tremor'" discusses the evolution of the term "dystonic tremor" and its different definitions over the years. The term was first introduced in the 1980s to describe a specific type of dystonia characterized by repetitive jerking movements resembling a tremor. In 1998, the definition was expanded to include any tremor occurring in a body part affected by dystonia. The article highlights the inconsistent use of the term in the literature and suggests the need for a more widely acceptable alternative. [Extracted from the article]

OBJECTIVE: To develop an automated algorithm to detect, quantify, and differentiate between tremor using pen-on-paper spirals. METHODS: Patients with essential tremor (n = 25), dystonic tremor (n = 25), Parkinson’s disease (n = 25), and healthy volunteers (HV, n = 25) drew free-hand spirals. The algorithm derived the mean deviation (MD) and tremor variability from scanned images. MD and tremor variability were compared with 1) the Bain and Findley scale, 2) the Fahn–Tolosa–Marin tremor rating scale (FTM–TRS), and 3) the peak power and total power of the accelerometer spectra. Inter and intra loop widths were computed to differentiate between the tremor. RESULTS: MD was higher in the tremor group (48.9±26.3) than in HV (26.4±5.3; p < 0.001). The cut-off value of 30.3 had 80.9% sensitivity and 76.0% specificity for the detection of the tremor [area under the curve: 0.83; 95% confidence index (CI): 0.75, 0.91, p < 0.001]. MD correlated with the Bain and Findley ratings (rho = 0.491, p = 0 < 0.001), FTM–TRS part B (rho = 0.260, p = 0.032) and accelerometric measures of postural tremor (total power, rho = 0.366, p < 0.001; peak power, rho = 0.402, p < 0.001). Minimum Detectable Change was 19.9%. Inter loop width distinguished Parkinson’s disease spirals from dystonic tremor (p < 0.001, 95% CI: 54.6, 211.1), essential tremor (p = 0.003, 95% CI: 28.5, 184.9), or HV (p = 0.036, 95% CI: -160.4, -3.9). CONCLUSION: The automated analysis of pen-on-paper spirals generated robust variables to quantify the tremor and putative variables to distinguish them from each other. SIGNIFICANCE: This technique maybe useful for epidemiological surveys and follow-up studies on tremor. [ABSTRACT FROM AUTHOR]

Background: Tremors other than those associated with Parkinson's disease (nonparkinsonian tremor) are commonly observed in clinical settings. However, their frequency and clinical characteristics have rarely been reported. Objectives: To classify non-parkinsonian tremors based on the consensus statement on the classification of tremors, from the task force of the International Parkinson and Movement Disorder Society published in 2018. Methods: A prospective registry at a tertiary care teaching institute. Results: A total of 475 patients with non-parkinsonian tremors were recruited for the study. 67.57% (n = 321) of our patients were male and a family history of tremor was present in 20.84% (n = 99) of patients. Dystonic tremor (DT) was the most common non-parkinsonian tremor (33.26%). 27.78% of patients fulfilled the new classification criteria for essential tremor, with 13.47% classified as pure ET (ET) and 14.31% exhibiting neurological soft signs, leading to the classification of ET plus (ETP). Patients with ETP had more family history (57.35%) [vs DT (26.48%, p = 0.00004) and ET (10.93%, p = 0.00003], longer duration of disease [mean ± standard deviation (SD) = 9.53 ± 8.64 years] [vs DT (5.60 ± 5.93, p = 0.0003) and ET (6.38 ± 5.97, p = 0.01) years], and more severe tremor as measured by the essential tremor rating assessment scale total score [mean ± SD = 27.42 ± 11.70] [vs DT (23.50 ± 8.62, p = 0.007) and ET (22.12 ± 8.19, p = 0.007)] compared with patients with DT and ET. Conclusions: DT was the most common cause of non-parkinsonian tremor in our registry followed by essential tremor syndrome. ETP was more common than ET. [ABSTRACT FROM AUTHOR]

Background: Patients with essential tremor (ET), Parkinson's disease (PD) and dystonic tremor (DT) can be difficult to classify and often share similar characteristics. Objectives: To use ubiquitous smartphone accelerometers with and without clinical features to automate tremor classification using supervised machine learning, and to use unsupervised learning to evaluate if natural clusterings of patients correspond to assigned clinical diagnoses. Methods: A supervised machine learning classifier was trained to classify 78 tremor patients using leave-one-out cross-validation to estimate performance on unseen accelerometer data. An independent cohort of 27 patients were also studied. Next, we focused on a subset of 48 patients with both smartphone-based tremor measurements and detailed clinical assessment metrics and compared two separate machine learning classifiers trained on these data. Results: The classifier yielded a total accuracy of 74.4% and F1-score of 0.74 for a trinary classification with an area under the curve of 0.904, average F1-score of 0.94, specificity of 97% and sensitivity of 84% in classifying PD from ET or DT. The algorithm classified ET from non-ET with 88% accuracy, but only classified DT from non-DT with 29% accuracy. A poorer performance was found in the independent cohort. Classifiers trained on accelerometer and clinical data respectively obtained similar results. Conclusions: Machine learning classifiers achieved a high accuracy of PD, however moderate accuracy of ET, and poor accuracy of DT classification. This underscores the difficulty of using AI to classify some tremors due to lack of specificity in clinical and neuropathological features, reinforcing that they may represent overlapping syndromes. [ABSTRACT FROM AUTHOR]

Background: Deep brain stimulation (DBS) has been proposed to treat disabling dystonic tremor (DT), but there is debate about the optimal target. DBS of the globus pallidus interna (GPi) may be insufficient to control tremor, and DBS of the ventral intermediate thalamic nucleus (VIM) may inadequately control dystonic features, raising the question of combining both targets.Objectives: To report the respective effects on DT symptoms of high-frequency stimulation of the VIM, the GPi and both targets simultaneously stimulated.Methods: Three patients with DT treated by bilateral high frequency DBS of 2 targets (VIM and GPi) were assessed 12 months after surgery in 4 conditions (VIM and GPi-DBS; GPi-DBS only; VIM-DBS only; DBS switched Off for both targets) by 3 independent movement disorders specialists blinded to the condition.Results: The Fahn-Tolosa-Marin-tremor-rating-scale (FTM-TRS) and Burke-Fahn-Marsden-dystonia-rating-scale (BFM-DRS) scores were more improved by combined DBS than VIM alone or GPi alone. Compared to Off/Off condition, mean total FTM-TRS score decrease was 34%, 42% and 63% respectively with VIM only, GPi only and combined VIM and GPi stimulation. Mean total BFM-DRS score decrease was 34%, 37% and 60% respectively with VIM only, GPi only and combined VIM and GPi stimulation, compared to Off/Off condition. Improvement concerned both motor, functional and activities of daily living sub-scores. No complications or adverse events were observed.Conclusion: Combined VIM- and GPi-DBS, by modulating the cerebello-thalamo-cortical network and the basal ganglia-thalamo-cortical network, both involved in DT pathophysiology, may be more efficient than single DBS targeting only one of them. [ABSTRACT FROM AUTHOR]

Introduction: The recently released classification has revised the nosology of tremor, defining essential tremor (ET) as a syndrome and fueling an enlightened debate about some newly conceptualized entities such as ET-plus. As a result, precise information of demographics, clinical features, and about the natural history of these conditions are lacking. Methods: The ITAlian tremor Network (TITAN) is a multicenter data collection platform, the aim of which is to prospectively assess, according to a standardized protocol, the phenomenology and natural history of tremor syndromes. Results: In the first year of activity, 679 patients have been recruited. The frequency of tremor syndromes varied from 32% of ET and 41% of ET-plus to less than 3% of rare forms, including focal tremors (2.30%), task-specific tremors (1.38%), isolated rest tremor (0.61%), and orthostatic tremor (0.61%). Patients with ET-plus were older and had a higher age at onset than ET, but a shorter disease duration, which might suggest that ET-plus is not a disease stage of ET. Familial aggregation of tremor and movement disorders was present in up to 60% of ET cases and in about 40% of patients with tremor combined with dystonia. The body site of tremor onset was different between tremor syndromes, with head tremor being most commonly, but not uniquely, associated with dystonia. Conclusions: The TITAN study is anticipated to provide clinically relevant prospective information about the clinical correlates of different tremor syndromes and their specific outcomes and might serve as a basis for future etiological, pathophysiological, and therapeutic research. [ABSTRACT FROM AUTHOR]

Background: Essential tremor (ET) and dystonic tremor (DT) are movement disorders that cause debilitating symptoms, significantly impacting daily activities and quality of life. A poor understanding of their pathophysiology, as well as the mediators of clinical outcomes following deep brain stimulation (DBS), highlights the need for biomarkers to accurately characterise and optimally treat patients., Objectives: We assessed the white matter microstructure of pathways implicated in the pathophysiology and therapeutic intervention in a retrospective cohort of patients with DT (n = 17) and ET (n = 19). We aimed to identity associations between white matter microstructure, upper limb tremor severity, and tremor improvement following DBS., Methods: A fixel-based analysis pipeline was implemented to investigate white matter microstructural metrics in the whole brain, cerebello-thalamic pathways and tracts connected to stimulation volumes following DBS. Associations with preoperative and postoperative severity were analysed within each disorder group and across combined disorder groups., Results: DBS led to significant improvements in both groups. No group differences in stimulation positions were identified. When white matter microstructural data was aligned according to the maximally affected upper limb, increased fiber density, and combined fiber density & cross-section of fixels in the left cerebellum were associated with greater tremor severity across DT and ET patients. White matter microstructure did not show associations with postoperative changes in cerebello-thalamic pathways, or tracts connected to stimulation volumes., Discussion: Diffusion changes of the cerebellum are associated with the severity of upper limb tremor and appear to overlap in essential or dystonic tremor disorders., Competing Interests: The authors have no competing interests to declare., (Copyright: © 2024 The Author(s).)

Since the initial description of Essential Tremor (ET), the entity of ET with rest tremor has proven to be a controversial concept. Some authors argued it could be a late manifestation of ET, others suggested it could be a variant of ET, yet others suggested it could represent a transitional state between ET and Parkinson's disease. The novel tremor classification has proposed the construct of ET-plus to differentiate patients with rest tremor from pure ET. However, there is no clarity of what ET-plus rest tremor represents. With the aim of shedding light on this controversial entity, we have, therefore, systematically reviewed all clinical, electrophysiological, imaging and anatomopathological studies indexed in the Medline database published both before and after the new tremor classification and involving patients with ET-plus rest tremor. Forty-four studies involving 4028 patients were included in this review and analyzed in detail by means of descriptive statistics. The results of the current review suggest that ET-plus rest tremor is a heterogenous group of conditions: thus, rest tremor might represent a late feature of ET, might reflect a different disorder with higher age at onset and lower dependance on genetic susceptibility than ET, might suggest the development of Parkinson's disease or might indicate a misdiagnosis of ET. The reviewed lines of evidence refuse recent claims arguing against the construct of ET-plus, which should be viewed as a syndrome with different possible underpinnings, and highlights methodological issues to be solved in future research. [ABSTRACT FROM AUTHOR]

Major progress has occurred during the last decade in the field of tremor. From the clinical standpoint, a new classification has completely revised the nosology of tremor syndromes and has re‐conceptualized essential tremor as a syndrome rather than a single disease entity, fueling an ongoing enlightened debate. Significant advances have been obtained in terms of instrumental measurement of tremor, remarking on the possibility of developing novel treatment strategies based on tremor characteristics, namely tremor‐phase. Moreover, a better understanding of the pathophysiological mechanisms has further led to the suggestion of refining the classification of tremor syndromes according to their driving underpinnings. Finally, surgical options such as deep brain stimulation and focused ultrasound thalamotomy are now part of the therapeutic portfolio for tremor, but several oral drugs, including long‐chain alcohols, T‐channel blockers, allosteric modulators of potassium channels, and of GABA‐A receptors, are currently being tested and hold promise. This review will discuss the key milestones in tremor research of the last 10 years, with a focus on the most common tremor syndromes, namely essential tremor, dystonic tremor, and Parkinsonian tremor. [ABSTRACT FROM AUTHOR]

SEE MOLL AND ENGEL DOI101093/AWW308 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Brain regions dynamically engage and disengage with one another to execute everyday actions from movement to decision making. Pathologies such as Parkinson's disease and tremor emerge when brain regions controlling movement cannot readily decouple, compromising motor function. Here, we propose a novel stimulation strategy that selectively regulates neural synchrony through phase-specific stimulation. We demonstrate for the first time the therapeutic potential of such a stimulation strategy for the treatment of patients with pathological tremor. Symptom suppression is achieved by delivering stimulation to the ventrolateral thalamus, timed according to the patient's tremor rhythm. Sustained locking of deep brain stimulation to a particular phase of tremor afforded clinically significant tremor relief (up to 87% tremor suppression) in selected patients with essential tremor despite delivering less than half the energy of conventional high frequency stimulation. Phase-specific stimulation efficacy depended on the resonant characteristics of the underlying tremor network. Selective regulation of neural synchrony through phase-locked stimulation has the potential to both increase the efficiency of therapy and to minimize stimulation-induced side effects.

Essential tremor (ET) and dystonic tremor (DT) are the two most common tremor disorders, and misdiagnoses are very common due to similar tremor symptoms. In this study, we explore the structural network mechanisms of ET and DT using brain grey matter (GM) morphological networks and combine those with machine learning models. 3D-T1 structural images of 75 ET patients, 71 DT patients, and 79 healthy controls (HCs) were acquired. We used voxel-based morphometry to obtain GM images and constructed GM morphological networks based on the Kullback-Leibler divergence-based similarity (KLS) method. We used the GM volumes, morphological relations, and global topological properties of GM-KLS morphological networks as input features. We employed three classifiers to perform the classification tasks. Moreover, we conducted correlation analysis between discriminative features and clinical characteristics. 16 morphological relations features and 1 global topological metric were identified as the discriminative features, and mainly involved the cerebello-thalamo-cortical circuits and the basal ganglia area. The Random Forest (RF) classifier achieved the best classification performance in the three-classification task, achieving a mean accuracy (mACC) of 78.7%, and was subsequently used for binary classification tasks. Specifically, the RF classifier demonstrated strong classification performance in distinguishing ET vs. HCs, ET vs. DT, and DT vs. HCs, with mACCs of 83.0 %, 95.2 %, and 89.3 %, respectively. Correlation analysis demonstrated that four discriminative features were significantly associated with the clinical characteristics. This study offers new insights into the structural network mechanisms of ET and DT. It demonstrates the effectiveness of combining GM-KLS morphological networks with machine learning models in distinguishing between ET, DT, and HCs. • The findings showed that the ML algorithms achieved good classification performance in classification tasks, the most powerful 17 discriminative features mainly involved the cerebello-thalamo-cortical circuits and basal ganglia area. • RF classifier to perform the classification tasks had achieved good results, especially in identifying DT from ET and HCs. • A significant proportion of discriminative features (15/17, 88.2 %) consistently showed morphological relations between frontal lobe and other brain regions were deemed as the most vital in distinguishing ET, DT, and HCs. • Using SHAP analysis and bounding by a feature importance greater than 0.05, the involvement of the middle frontal gyrus, anterior cingulate and paracingulate gyri, and lingual gyrus were characteristic alterations of ET; the involvement of the SMA, vermis_4_5, and putamen were characteristic alterations of DT. [ABSTRACT FROM AUTHOR]

Tremor is part of the phenomenological spectrum of dystonia. Treatments available for tremor in dystonia are oral medications (OM), botulinum neurotoxin (BoNT), and brain surgery (deep brain stimulation or thalamotomy). There is limited knowledge regarding the outcome of different treatment options, and evidence is especially scarce for the tremor of the upper limbs occurring in people with dystonia. In this single-center retrospective study, we evaluated the outcome of different treatments in a cohort of people with upper limb dystonic tremors. Demographic, clinical, and treatment data were analyzed. Dropout rates and side effects were specifically assessed, as well as the 7-point patient-completed clinical global impression scale (p-CGI-S, 1: very much improved; 7: very much worse) as outcome measures. A total of 47 subjects (46.8% female) with dystonic tremor, tremor associated with dystonia, or task-specific tremor were included, with a median age at onset of 58 years (7–86). A total of 31 subjects were treated with OM, 31 with BoNT, and 7 with surgery. Dropout rates with OM were 74.2% due to either lack of efficacy (n = 10) or side effects (n = 13). A total of 7 patients treated with BoNT (22.6%) had mild weakness, causing dropout in 2. P-CGI-S was ≤3 (improvement) in 39% with OM, compared to 92% with BoNT and 100% with surgery. These findings suggest good symptom control of the tremor of the upper limb in dystonia with BoNT and surgery, with higher rates of dropout and side effects with OM. Randomized controlled studies are needed to confirm our findings and provide further insight into better selecting suitable patients for BoNT or brain surgery.

• This chapter provides an overview of clinical and electrophysiological tools for measuring and classifying tremor. • The distinguishing clinical and electrophysiologic features of the different forms of tremor are explained. • The pathophysiology of the different tremors is reviewed with an emphasis on electrophysiological methods. The various forms of tremor are now classified in two axes: clinical characteristics (axis 1) and etiology (axis 2). Electrophysiology is an extension of the clinical exam. Electrophysiologic tests are diagnostic of physiologic tremor, primary orthostatic tremor, and functional tremor, but they are valuable in the clinical characterization of all forms of tremor. Electrophysiology will likely play an increasing role in axis 1 tremor classification because many features of tremor are not reliably assessed by clinical examination alone. In particular, electrophysiology may be needed to distinguish tremor from tremor mimics, assess tremor frequency, assess tremor rhythmicity or regularity, distinguish mechanical-reflex oscillation from central neurogenic oscillation, determine if tremors in different body parts, muscles, or brain regions are strongly correlated, document tremor suppression or entrainment by voluntary movements of contralateral body parts, and document the effects of voluntary movement on rest tremor. In addition, electrophysiologic brain mapping has been crucial in our understanding of tremor pathophysiology. The electrophysiologic methods of tremor analysis are reviewed in the context of physiologic tremor and pathologic tremors, with a focus on clinical characterization and pathophysiology. Electrophysiology is instrumental in elucidating tremor mechanisms, and the pathophysiology of the different forms of tremor is summarized in this review. [ABSTRACT FROM AUTHOR]

Despite recent advances in tremor and dystonia classification, it remains difficult to discriminate essential tremor from dystonic tremor as they are similar in appearance and no biomarker exists. Further, tremor can appear in the same or a different body part than the dystonia. The aim of the current study was to better understand the differential pathophysiology of these tremors.We designed a cross-sectional case-control study and recruited 16 patients with essential tremor, 16 patients with dystonic tremor, and 17 age-matched healthy volunteers. We used multi-modal imaging combining resting-state functional MRI, diffusion tensor imaging, and magnetic resonance spectroscopy. We measured functional connectivity of resting-state fMRI to assess connectivity in the tremor network, fractional anisotropy and mean diffusivity with diffusion tensor imaging, and GABA+, Glutamate/Glutamine, Choline, and N-Acetylaspartate with spectroscopy (adjusted to Creatine).Our results showed reduced functional connectivity of resting-state fMRI between the cerebellum and dentate nucleus bilaterally for the essential tremor group, but not the dystonic tremor group, compared to healthy volunteers. There was higher fractional anisotropy in the middle cerebellar peduncle bilaterally for the dystonic tremor group compared to the essential tremor group as well as for essential tremor group compared to healthy volunteers. There was also higher fractional anisotropy in the red nucleus and corticospinal tract for essential tremor and dystonic tremor groups compared to healthy volunteers. We also showed reduced mean diffusivity in the cerebellum of both essential tremor and dystonic tremor groups compared to healthy volunteers. Finally, we found elevated GABA+/Cr in the cerebellum of the essential tremor and dystonic tremor groups compared to healthy volunteers, but no difference emerged between essential tremor and dystonic tremor groups. We did not find group differences in the other metabolites.Our results indicate cerebellar alterations in essential tremor and dystonic tremor patients compared to healthy volunteers, and further changes in the cerebellum network for the dystonic tremor patients. suggesting that the cerebellum is affected differently in both tremors.

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.

Introduction: Bradykinesia is an essential diagnostic criterion for Parkinson's disease (PD) but is frequently observed in many non-parkinsonian movement disorders, complicating differential diagnosis, particularly in disorders featuring tremors. The presence of bradykinetic features in the subset of dystonic tremors (DT), either "pure" dystonic tremors or tremors associated with dystonia, remains currently unexplored. The aim of the current study was to evaluate upper limb bradykinesia in DT patients, comparing them with healthy controls (HC) and patients with PD by observing repetitive finger tapping (FT)., Methods: The protocol consisted of two main parts. Initially, the kinematic recording of repetitive FT was performed using optical hand tracking system (Leap Motion Controller). The values of amplitude, amplitude decrement, frequency, frequency decrement, speed, acceleration and number of halts of FT were calculated. Subsequently, three independent movement disorder specialists from different movement disorders centres, blinded to the diagnosis, rated the presence of FT bradykinesia based on video recordings., Results: Thirty-six subjects participated in the study (12 DT, 12 HC and 12 early-stage PD). Kinematic analysis revealed no significant difference in the selected parameters of FT bradykinesia between DT patients and HC. In comparisons between DT and PD patients, PD patients exhibited bigger amplitude decrement and slower FT performance. In the blinded clinical assessment, bradykinesia was rated, on average, as being present in 41.6% of DT patients, 27.7% of HC, and 91.7% of PD patients. While overall inter-rater agreement was moderate, weak agreement was noted within the DT group., Discussion: Clinical ratings indicated signs of bradykinesia in almost half of DT patients. The objective kinematic analysis confirmed comparable parameters between DT and HC individuals, with more pronounced abnormalities in PD across various kinematic parameters. Interpretation of bradykinesia signs in tremor patients with DT should be approached cautiously and objective motion analysis might complement the diagnostic process and serve as a decision support system in the choice of clinical entities., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Matejicka, Kajan, Goga, Straka, Balaz, Janovic, Minar, Valkovic, Hajduk and Kosutzka.)

This article is a reply to a previous article on neuropathic tremor in Guillain Barré Syndrome. The authors thank the previous authors for their interest and highlight an important treatment option for neuropathic tremor following Guillain Barré Syndrome. They discuss the similarities between their series of patients and the patient reported by the previous authors, as well as the different treatment responses observed. The authors also provide a pathophysiological explanation for the potential effectiveness of pregabalin in treating neuropathic tremor. They conclude by suggesting that propranolol, pregabalin, and gabapentin may be initial medications to be tried for neuropathic tremors, but further studies are needed to understand the natural history and therapeutic response of this disorder. [Extracted from the article]

Transcranial magnetic stimulation (TMS) is a painless, non-invasive, and established brain stimulation technique to investigate human brain function. Over the last three decades, TMS has shed insight into the pathophysiology of many neurological disorders. Tremor is an involuntary, rhythmic oscillatory movement disorder commonly related to pathological oscillations propagated via the cerebello-thalamo-cortical pathway. Although tremor is the most common movement disorder and recent imaging studies have enhanced our understanding of the critical pathogenic networks, the underlying pathophysiology of different tremor syndromes is complex and still not fully understood. TMS has been used as a tool to further our understanding of tremor pathophysiology. In addition, repetitive TMS (rTMS) that can modulate brain functions through plasticity effects has been targeted to the tremor network to gain potential therapeutic benefits. However, evidence is available for only a few studies that included small patient samples with limited clinical follow-up. This review aims to discuss the role of TMS in advancing the pathophysiological understanding as well as emerging applications of rTMS for treating individual tremor syndromes. The review will focus on essential tremor, Parkinson's disease tremor, dystonic tremor syndrome, orthostatic tremor, and functional tremor. [ABSTRACT FROM AUTHOR]

Deep brain stimulation (DBS) of the thalamus is an effective treatment for medically refractory essential, dystonic and Parkinson's tremor. It may also provide benefit in less common tremor syndromes including, post-traumatic, cerebellar, Holmes, neuropathic and orthostatic tremor. The long-term benefit of DBS in essential and dystonic tremor (ET/DT) often wanes over time, a phenomena referred to as stimulation "tolerance" or "habituation". While habituation is generally accepted to exist, it remains controversial. Attempts to quantify habituation have revealed conflicting reports. Placebo effects, loss of micro-lesional effect, disease related progression, suboptimal stimulation and stimulation related side-effects may all contribute to the loss of sustained long-term therapeutic effect. Habituation often presents as substantial loss of initial DBS benefit occurring as early as a few months after initial stimulation; a complex and feared issue when faced in the setting of optimal electrode placement. Simply increasing stimulation current tends only to propagate tremor severity and induce stimulation related side effects. The report by Paschen and colleagues of worsening tremor scores in the "On" vs. "Off" stimulation state over time, even after accounting for "rebound" tremor, supports the concept of habituation. However, these findings have not been consistent across all studies. Chronic high intensity stimulation has been hypothesized to induce detrimental plastic effects on tremor networks, with some lines of evidence that DT and ET may be more susceptible than Parkinson's tremor to habituation. However, Tsuboi and colleague's recent longitudinal follow-up in dystonic and "pure" essential tremor suggests otherwise. Alternatively, post-mortem findings support a biological adaption to stimulation. The prevalence and etiology of habituation is still not fully understood and management remains difficult. A recent study reported that alternating thalamic stimulation parameters at weekly intervals provided improved stability of tremor control consistent with reduced habituation. In this article the available evidence for habituation after DBS for tremor syndromes is reviewed; including its prevalence, time-course, possible mechanisms; along with expected long-term outcomes for tremor and factors that may assist in predicting, preventing and managing habituation. [ABSTRACT FROM AUTHOR]

Deep brain stimulation (DBS) of the thalamus is an effective treatment for medically refractory essential, dystonic and Parkinson's tremor. It may also provide benefit in less common tremor syndromes including, post-traumatic, cerebellar, Holmes, neuropathic and orthostatic tremor. The long-term benefit of DBS in essential and dystonic tremor (ET/DT) often wanes over time, a phenomena referred to as stimulation “tolerance” or “habituation”. While habituation is generally accepted to exist, it remains controversial. Attempts to quantify habituation have revealed conflicting reports. Placebo effects, loss of micro-lesional effect, disease related progression, suboptimal stimulation and stimulation related side-effects may all contribute to the loss of sustained long-term therapeutic effect. Habituation often presents as substantial loss of initial DBS benefit occurring as early as a few months after initial stimulation; a complex and feared issue when faced in the setting of optimal electrode placement. Simply increasing stimulation current tends only to propagate tremor severity and induce stimulation related side effects. The report by Paschen and colleagues of worsening tremor scores in the “On” vs. “Off” stimulation state over time, even after accounting for “rebound” tremor, supports the concept of habituation. However, these findings have not been consistent across all studies. Chronic high intensity stimulation has been hypothesized to induce detrimental plastic effects on tremor networks, with some lines of evidence that DT and ET may be more susceptible than Parkinson's tremor to habituation. However, Tsuboi and colleague's recent longitudinal follow-up in dystonic and “pure” essential tremor suggests otherwise. Alternatively, post-mortem findings support a biological adaption to stimulation. The prevalence and etiology of habituation is still not fully understood and management remains difficult. A recent study reported that alternating thalamic stimulation parameters at weekly intervals provided improved stability of tremor control consistent with reduced habituation. In this article the available evidence for habituation after DBS for tremor syndromes is reviewed; including its prevalence, time-course, possible mechanisms; along with expected long-term outcomes for tremor and factors that may assist in predicting, preventing and managing habituation.

Transcranial magnetic stimulation (TMS) is a painless, non-invasive, and established brain stimulation technique to investigate human brain function. Over the last three decades, TMS has shed insight into the pathophysiology of many neurological disorders. Tremor is an involuntary, rhythmic oscillatory movement disorder commonly related to pathological oscillations propagated via the cerebello-thalamo-cortical pathway. Although tremor is the most common movement disorder and recent imaging studies have enhanced our understanding of the critical pathogenic networks, the underlying pathophysiology of different tremor syndromes is complex and still not fully understood. TMS has been used as a tool to further our understanding of tremor pathophysiology. In addition, repetitive TMS (rTMS) that can modulate brain functions through plasticity effects has been targeted to the tremor network to gain potential therapeutic benefits. However, evidence is available for only a few studies that included small patient samples with limited clinical follow-up. This review aims to discuss the role of TMS in advancing the pathophysiological understanding as well as emerging applications of rTMS for treating individual tremor syndromes. The review will focus on essential tremor, Parkinson's disease tremor, dystonic tremor syndrome, orthostatic tremor, and functional tremor.

Tremor is the most commonly encountered movement disorder in clinical practice. A wide range of pathologies may manifest with tremor either as a presenting or predominant symptom. Considering the marked etiological and phenomenological heterogeneity, it would be desirable to develop a classification of tremors that reflects their underlying pathophysiology. The tremor task force of the International Parkinson Disease and Movement Disorders Society has worked toward this goal and proposed a new classification system. This system has remained a prime topic of scientific communications on tremor in recent times. The new classification is based on two axes: 1. based on the clinical features, history, and tremor characteristics and 2. based on the etiology of tremor. In this article, we discuss the key aspects of the new classification, review various tremor syndromes, highlight some of the controversies in the field of tremor, and share the potential future perspectives.

Tremor is the most commonly encountered movement disorder in clinical practice. A wide range of pathologies may manifest with tremor either as a presenting or predominant symptom. Considering the marked etiological and phenomenological heterogeneity, it would be desirable to develop a classification of tremors that reflects their underlying pathophysiology. The tremor task force of the International Parkinson Disease and Movement Disorders Society has worked toward this goal and proposed a new classification system. This system has remained a prime topic of scientific communications on tremor in recent times. The new classification is based on two axes: 1. based on the clinical features, history, and tremor characteristics and 2. based on the etiology of tremor. In this article, we discuss the key aspects of the new classification, review various tremor syndromes, highlight some of the controversies in the field of tremor, and share the potential future perspectives. [ABSTRACT FROM AUTHOR]

Background: It has been debated for decades whether primary writing tremor is a form of dystonic tremor, a variant of essential tremor, or a separate entity. We wished to test the hypothesis that primary writing tremor and dystonia share a common pathophysiology. Objectives: The objective of the present study was to investigate the pathophysiological hallmarks of dystonia in patients affected by primary writing tremor. Methods: Ten patients with idiopathic dystonic tremor syndrome, 7 with primary writing tremor, 10 with essential tremor, and 10 healthy subjects were recruited. They underwent eyeblink classic conditioning, blink recovery cycle, and transcranial magnetic stimulation assessment, including motor‐evoked potentials and short‐ and long‐interval intracortical inhibition at baseline. Transcranial magnetic stimulation measures were also recorded after paired‐associative plasticity protocol. Results: Primary writing tremor and dystonic tremor syndrome had a similar pattern of electrophysiological abnormalities, consisting of reduced eyeblink classic conditioning learning, reduced blink recovery cycle inhibition, and a lack of effect of paired‐associative plasticity on long‐interval intracortical inhibition. The latter 2 differ from those obtained in essential tremor and healthy subjects. Although not significant, slightly reduced short‐interval intracortical inhibition and a larger effect of paired‐associative plasticity in primary writing tremor and dystonic tremor syndrome, compared with essential tremor and healthy subjects, was observed. Conclusions: Our initial hypothesis of a common pathophysiology between dystonia and primary writing tremor has been confirmed. Primary writing tremor might be considered a form of dystonic tremor. © 2021 International Parkinson and Movement Disorder Society [ABSTRACT FROM AUTHOR]

The pathophysiology of dystonic tremor and essential tremor remains partially understood. In patients with medication-refractory dystonic tremor or essential tremor, deep brain stimulation (DBS) targeting the thalamus or posterior subthalamic area has evolved into a promising treatment option. However, the optimal DBS targets for these disorders remains unknown. This retrospective study explored the optimal targets for DBS in essential tremor and dystonic tremor using a combination of volumes of tissue activated estimation and functional and structural connectivity analyses. We included 20 patients with dystonic tremor who underwent unilateral thalamic DBS, along with a matched cohort of 20 patients with essential tremor DBS. Tremor severity was assessed preoperatively and approximately 6 months after DBS implantation using the Fahn-Tolosa-Marin Tremor Rating Scale. The tremor-suppressing effects of DBS were estimated using the percentage improvement in the unilateral tremor-rating scale score contralateral to the side of implantation. The optimal stimulation region, based on the cluster centre of gravity for peak contralateral motor score improvement, for essential tremor was located in the ventral intermediate nucleus region and for dystonic tremor in the ventralis oralis posterior nucleus region along the ventral intermediate nucleus/ventralis oralis posterior nucleus border (4 mm anterior and 3 mm superior to that for essential tremor). Both disorders showed similar functional connectivity patterns: a positive correlation between tremor improvement and involvement of the primary sensorimotor, secondary motor and associative prefrontal regions. Tremor improvement, however, was tightly correlated with the primary sensorimotor regions in essential tremor, whereas in dystonic tremor, the correlation was tighter with the premotor and prefrontal regions. The dentato-rubro-thalamic tract, comprising the decussating and non-decussating fibres, significantly correlated with tremor improvement in both dystonic and essential tremor. In contrast, the pallidothalamic tracts, which primarily project to the ventralis oralis posterior nucleus region, significantly correlated with tremor improvement only in dystonic tremor. Our findings support the hypothesis that the pathophysiology underpinning dystonic tremor involves both the cerebello-thalamo-cortical network and the basal ganglia-thalamo-cortical network. Further our data suggest that the pathophysiology of essential tremor is primarily attributable to the abnormalities within the cerebello-thalamo-cortical network. We conclude that the ventral intermediate nucleus/ventralis oralis posterior nucleus border and ventral intermediate nucleus region may be a reasonable DBS target for patients with medication-refractory dystonic tremor and essential tremor, respectively. Uncovering the pathophysiology of these disorders may in the future aid in further improving DBS outcomes. [ABSTRACT FROM AUTHOR]