Pharmacotherapy of essential tremor

Stereotactic radiosurgery in the treatment of essential tremor - a systematic review

Introduction

Essential tremor (ET) is the most common movement disorder in adults, with an estimated incidence of up to 1% of the population and 5% of people older than 65 years of age. ET is manifested primarily by bilateral postural and kinetic tremor of the upper limbs with or without neurological symptoms and cognitive deficits. ET disrupts daily tasks and significantly lowers quality of life. Currently available medications alone are often insufficient to control severe symptoms. Several surgical treatment options are available, including stereotactic radiosurgery (SRS)-a minimally invasive treatment option aimed at relieving and controlling tremors.

Methods

We conducted a systematic review of the scientific literature on the use of SRS in the treatment of ET using PubMed, Scopus, Web of Science, Cochrane, ScienceDirect, and ClinicalTrials.gov registry and adhered to the PRISMA guidelines.

Results

The results obtained confirm the high efficacy and safety of the SRS procedure in treating drug-resistant intention tremor. The study results present high response rate reaching 80% and achievement of manual task improvement, lessening of the tremor and increase in the quality of life of the majority of the operated patients. The method also stands out for its favorable balance between efficiency and cost.

Disscusion

Stereotactic radiosurgery is a favourable, safe, efficient and cost-effective method in treatment of the essential tremor. Ongoing research is crucial to refine patient selection criteria for this procedure and further improve the effectiveness of the technique.

A Randomized Phase 2 KINETIC Trial Evaluating SAGE-324/BIIB124 in Individuals with Essential Tremor

BACKGROUND

SAGE-324/BIIB124 is an investigational positive allosteric modulator of GABAA receptors.

OBJECTIVE

KINETIC (NCT04305275), a double-blind, randomized, placebo-controlled, phase 2 study, evaluated SAGE-324/BIIB124 in individuals with essential tremor (ET).

METHODS

Individuals aged 18 to 80 years were randomly assigned 1:1 to orally receive 60 mg of SAGE-324/BIIB124 or placebo once daily for 28 days. The primary endpoint was change from baseline in The Essential Tremor Rating Assessment Scale-Performance Subscale (TETRAS-PS) Item 4 (upper-limb tremor) at day 29 with SAGE-324/BIIB124 versus placebo.

RESULTS

Between May 2020 and February 2021, 69 U.S. participants were randomly assigned to receive SAGE-324/BIIB124 (n = 34) or placebo (n = 35). There was a significant reduction from baseline in TETRAS-PS Item 4 at day 29 with SAGE-324/BIIB124 versus placebo (least squares mean [standard error]: -2.31 [0.401] vs. -1.24 [0.349], P = 0.0491). The most common treatment-emergent adverse events included somnolence, dizziness, fatigue, and balance disorder.

CONCLUSION

These results support further development of SAGE-324/BIIB124 for potential ET treatment. © 2024 Sage Therapeutics, Inc and The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Voice Improvement After Essential Tremor Treatment via Focused Ultrasound and Deep Brain Stimulation

OBJECTIVES

The primary objective of this study was to determine whether two neurosurgical procedures, deep brain stimulation (DBS) and focused ultrasound (FUS), to treat essential tremor (ET) of the upper limb also reduce vocal tremor (VT) in patients with comorbid dysphonia.

METHODS

Twelve patients with ET and concomitant VT scheduled for neurosurgical intervention (FUS or DBS) or returning for follow-up after DBS implantation were assessed. FUS patients were assessed pre- and post-intervention and DBS patients were assessed with the electrodes turned on and off post-implantation. Three voice recordings of a sustained /a/ were obtained for each participant condition. Percent fundamental frequency variability (FFV) was calculated for each recorded sustained vowel. Additionally, blinded expert perceptual VT rating (VTR) was performed to assess subjective changes in tremors.

RESULTS

Of the 12 patients, seven underwent unilateral FUS, and five underwent bilateral DBS. Mean FFV without neurosurgical intervention was 18.3%, SD = 7.8 and with neurosurgical intervention was 6.3%, SD = 3.0 (t (70) =8.7, p < 0.001). Mean FFV decreased in the FUS cohort from 22.0%, SD = 7.1 pre-ablation to 6.7%, SD = 2.4 post-ablation (t (40) = 7.7, p < 0.001). Mean FFV also decreased in the DBS cohort from 15.7%, SD = 7.0 to 6.0%, SD = 3.3 when stimulation was turned on (t (28)=5.7 p < 0.001). In the FUS group, mean VTR decreased from 4.0 to 1.4 post-ablation (Z = 7.8, p < 0.001). In the DBS group, mean VTR decreased from 3.3 to 2.1 with stimulation (Z = 4.1, p < 0.001).

CONCLUSION

Neurosurgical interventions for ET (bilateral DBS and unilateral FUS) demonstrate acoustic and perceptual benefits for VT.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:367-373, 2024.

GABA-A Alpha 2/3 but Not Alpha 1 Receptor Subunit Ligand Inhibits Harmaline and Pimozide-Induced Tremor in Rats

Treatment of tremors, such as in essential tremor (ET) and Parkinson's disease (PD) is mostly ineffective. Exact tremor pathomechanisms are unknown and relevant animal models are missing. GABA-A receptor is a target for tremorolytic medications, but current non-selective drugs produce side effects and have safety liabilities. The aim of this study was a search for GABA-A subunit-specific tremorolytics using different tremor-generating mechanisms. Two selective positive allosteric modulators (PAMs) were tested. Zolpidem, targeting GABA-A α1, was not effective in models of harmaline-induced ET, pimozide- or tetrabenazine-induced tremulous jaw movements (TJMs), while the novel GABA-A α2/3 selective MP-III-024 significantly reduced both the harmaline-induced ET tremor and pimozide-induced TJMs. While zolpidem decreased the locomotor activity of the rats, MP-III-024 produced small increases. These results provide important new clues into tremor suppression mechanisms initiated by the enhancement of GABA-driven inhibition in pathways controlled by α2/3 but not α1 containing GABA-A receptors. Tremor suppression by MP-III-024 provides a compelling reason to consider selective PAMs targeting α2/3-containing GABA-A receptors as novel therapeutic drug targets for ET and PD-associated tremor. The possibility of the improved tolerability and safety of this mechanism over non-selective GABA potentiation provides an additional rationale to further pursue the selective α2/3 hypothesis.

Beta-Adrenergic Receptor Blockade Effects on Cardio-Pulmonary Exercise Testing in Healthy Young Adults: A Randomized, Placebo-Controlled Trial

BACKGROUND

Beta-blockers are increasingly prescribed while the effects of beta-adrenergic receptor blockade on cardio-pulmonary exercise test (CPET)-derived parameters remain under-studied.

METHODS

Twenty-one young healthy adults repeated three CPET at the same time with an interval of 7 days between each test. The tests were performed 3 h after a random, double-blind, cross-over single-dose intake of placebo, 2.5 mg or 5.0 mg bisoprolol, a cardio-selective beta1-adrenoreceptor antagonist. Gas exchange, heart rate (HR) and blood pressure (BP) were measured at rest and during cyclo-ergometric incremental CPET.

RESULTS

Maximal workload and VO₂max were unaffected by the treatment, with maximal respiratory exchange ratio > 1.15 in all tests. A beta-blocker dose-dependent effect reduced resting and maximal BP and HR and the chronotropic response to exercise, evaluated by the HR/VO₂ slope (placebo: 2.9 ± 0.4 beat/ml/kg; 2.5 mg bisoprolol: 2.4 ± 0.5 beat/ml/kg; 5.0 mg bisoprolol: 2.3 ± 0.4 beat/ml/kg, p < 0.001). Ventilation efficiency measured by the VE/VCO₂ slope and the ventilatory equivalent for CO₂ at the ventilatory threshold were not affected by beta1-receptor blockade. Post-exercise chronotropic recovery measured after 1 min was enhanced under beta1-blocker (placebo: 26 ± 7 bpm; 2.5 mg bisoprolol: 32 ± 6 bpm; 5.0 mg bisoprolol: 33 ± 6 bpm, p < 0.01).

CONCLUSION

The present results suggest that a single dose of bisoprolol does not affect metabolism, respiratory response and exercise capacity. However, beta-adrenergic blockade dose dependently reduces exercise hemodynamic response by lowering BP and the chronotropic response.

Propranolol Modulates Cerebellar Circuit Activity and Reduces Tremor

Tremor is the most common movement disorder. Several drugs reduce tremor severity, but no cures are available. Propranolol, a β-adrenergic receptor blocker, is the leading treatment for tremor. However, the in vivo circuit mechanisms by which propranolol decreases tremor remain unclear. Here, we test whether propranolol modulates activity in the cerebellum, a key node in the tremor network. We investigated the effects of propranolol in healthy control mice and Car8^wdl/wdl mice, which exhibit pathophysiological tremor and ataxia due to cerebellar dysfunction. Propranolol reduced physiological tremor in control mice and reduced pathophysiological tremor in Car8^wdl/wdl mice to control levels. Open field and footprinting assays showed that propranolol did not correct ataxia in Car8^wdl/wdl mice. In vivo recordings in awake mice revealed that propranolol modulates the spiking activity of control and Car8^wdl/wdl Purkinje cells. Recordings in cerebellar nuclei neurons, the targets of Purkinje cells, also revealed altered activity in propranolol-treated control and Car8^wdl/wdl mice. Next, we tested whether propranolol reduces tremor through β₁ and β₂ adrenergic receptors. Propranolol did not change tremor amplitude or cerebellar nuclei activity in β₁ and β₂ null mice or Car8^wdl/wdl mice lacking β₁ and β₂ receptor function. These data show that propranolol can modulate cerebellar circuit activity through β-adrenergic receptors and may contribute to tremor therapeutics.

Real-World Evidence of Transcutaneous Afferent Patterned Stimulation for Essential Tremor

Background

Transcutaneous afferent patterned stimulation (TAPS) is a prescription, wrist-worn device-delivered, non-invasive neuromodulation therapy for treatment of hand tremor in patients with essential tremor (ET). This retrospective post-market surveillance study evaluated real-world effectiveness of TAPS from patients using therapy on-demand for at least 90 days between August 2019 through June 2021.

Methods

Demographics were summarized from TAPS prescriptions received from the patient's healthcare provider. Therapy usage and effectiveness were analyzed from device logs, which included tremor measurements from onboard motion sensors. Tremor history and patient-reported outcomes were assessed from a voluntary survey.

Results

A total of 321 patients (average age 71 years, 32% female) met the criteria for this analysis, 216 of whom had tremor measurements available for analysis and 69 of whom completed the survey. Total usage period ranged from 90 to 663 days, with 28% of patients using the device for over one year. Patients used therapy 5.4 ± 4.5 (mean ± 1 standard deviation) times per week. TAPS reduced tremor power by 71% (geometric mean) across all sessions, with 59% of patients experiencing >50% tremor reduction after their sessions. Eighty-four percent (84%) of patients who returned the voluntary survey reported improvement in at least one of eating, drinking, or writing, and 65% of patients reported improvement in quality of life. Self-reported device-related safety complaints were consistent with adverse events in prior clinical trials.

Discussion

Real-world evidence is consistent with prior clinical trials and confirms TAPS provides safe and effective tremor control for many patients with ET. Future work assessing multi-year safety and effectiveness would be valuable to extend these data.

Association of Diet With Essential Tremor: A Narrative Review

Essential tremor is a neurological disorder categorized by the rhythmic shaking of the upper limbs, lower limbs, neck, or head. The etiology of essential tremor is believed to be genetic variations, environmental factors, lifestyle, etc. Poor lifestyle and diet are important factors contributing to the onset of various disorders. Environment and lifestyle play a significant part in the dietary habits of an individual. Some diet components may probably be associated with the etiopathogenesis or progression of the essential tremor. Dietary habits may be a key influence on the commencement of tremors in healthy individuals. Typically, the diet of essential tremor patients is not supervised. It may also intensify the tremors in essential tremor patients. Association of the diet with the essential tremor can shed light on the root of tremor aggravating aspect and aid in diet modification in essential tremor patients. The aim of the review is to establish a relation between the diet with etiopathogenesis and the progression of essential tremor. The review includes studies providing information about essential tremor and correlating essential tremor with diet, lifestyle, environment, and genetic factors. Studies that did not provide a link to the association of essential tremor were excluded. The interpretation of the research indicated that genetic variations might be triggered due to enzymatic changes triggered by dietary patterns. Dietary components showed ambiguous, weak, strong, or no association. Essential tremor may be influenced by diet. Further research must be carried out on essential tremor patients in the nutritional domain. Physicians may monitor the diet of the essential tremor patients and record the progress of the disorder on its basis to manage the patients with essential tremor and provide better services.

Transcriptomic effects of propranolol and primidone converge on molecular pathways relevant to essential tremor

Essential tremor (ET) is one of the most common movement disorders, affecting nearly 5% of individuals over 65 years old. Despite this, few genetic risk loci for ET have been identified. Recent advances in pharmacogenomics have previously been useful to identify disease related molecular targets. Notably, gene expression has proven to be quite successful for the inference of drug response in cell models. We sought to leverage this approach in the context of ET where many patients are responsive to two drugs: propranolol and primidone. In this study, cerebellar DAOY and neural progenitor cells were treated for 5 days with clinical concentrations of propranolol and primidone, after which RNA-sequencing was used to identify convergent differentially expressed genes across treatments. Propranolol was found to affect the expression of genes previously associated with ET and other movement disorders such as TRAPPC11. Pathway enrichment analysis of these convergent drug-targeted genes identified multiple terms related to calcium signaling, endosomal sorting, axon guidance, and neuronal morphology. Furthermore, genes targeted by ET drugs were enriched within cell types having high expression of ET-related genes in both cortical and cerebellar tissues. Altogether, our results highlight potential cellular and molecular mechanisms associated with tremor reduction and identify relevant genetic biomarkers for drug-responsiveness in ET.

Reduction of neuronal hyperexcitability with modulation of T-type calcium channel or SK channel in essential tremor

Essential tremor is one of the most prevalent movement disorders. Propranolol and primidone are the first-line pharmacological therapies. They provide symptomatic control in less than 50% of patients. Topiramate, alprazolam, clonazepam, gabapentin, and botulinum toxin injections are the next line of treatments. These medications lead to modest improvements and are therefore commonly used as add-on agents. Surgical therapies, including deep brain stimulation (DBS) surgery and focused ultrasound beam targeted to the thalamus, are considered for treating tremor refractory to medications and lead to greater than 75% improvements in tremor symptoms. However, DBS is a costly and an invasive procedure; some patients report tolerance to benefits. Focused ultrasound therapy leading to brain lesions is associated with a possibility for permanent clinical deficits. Therefore, research efforts to develop the next generation of oral medications with greater benefits and lesser adverse effects are warranted. There is considerable evidence that the increased functions of calcium channels (P/Q-type and T-type channels) and reduced functions of calcium-activated potassium channels (SK channels) located in the neuronal membranes lead to tremor oscillations. Consequently, many new pharmacological studies have targeted these channels to leverage better clinical outcomes. The current review will discuss the pathophysiology, the specific importance of these channels, and the early clinical experience of using compounds targeting these channels to treat essential tremor.

Mechanism of stress-induced attacks in an episodic neurologic disorder

Stress is the most common trigger among episodic neurologic disorders. In episodic ataxia type 2 (EA2), physical or emotional stress causes episodes of severe motor dysfunction that manifest as ataxia and dystonia. We used the tottering (tg/tg) mouse, a faithful animal model of EA2, to dissect the mechanisms underlying stress-induced motor attacks. We find that in response to acute stress, activation of α1-adrenergic receptors (α1-Rs) on Purkinje cells by norepinephrine leads to their erratic firing and consequently motor attacks. We show that norepinephrine induces erratic firing of Purkinje cells by disrupting their spontaneous intrinsic pacemaking via a casein kinase 2 (CK2)-dependent signaling pathway, which likely reduces the activity of calcium-dependent potassium channels. Moreover, we report that disruption of this signaling cascade at a number of nodes prevents stress-induced attacks in the tottering mouse. Together, our results suggest that norepinephrine and CK2 are required for the initiation of stress-induced attacks in EA2 and provide previously unidentified targets for therapeutic intervention.

Essential tremor: Clinical perspectives and pathophysiology

Essential tremor (ET) is one of the most common neurological disorders and can be highly disabling. In recent years, studies on the clinical perspectives and pathophysiology have advanced our understanding of ET. Specifically, clinical heterogeneity of ET, with co-existence of tremor and other neurological features such as dystonia, ataxia, and cognitive dysfunction, has been identified. The cerebellum has been found to be the key brain region for tremor generation, and structural alterations of the cerebellum have been extensively studied in ET. Finally, four main ET pathophysiologies have been proposed: 1) environmental exposures to β-carboline alkaloids and the consequent olivocerebellar hyper-excitation, 2) cerebellar GABA deficiency, 3) climbing fiber synaptic pathology with related cerebellar oscillatory activity, 4) extra-cerebellar oscillatory activity. While these four theories are not mutually exclusive, they can represent distinctive ET subtypes, indicating multiple types of abnormal brain circuitry can lead to action tremor. This article is part of the Special Issue "Tremor" edited by Daniel D. Truong, Mark Hallett, and Aasef Shaikh.

The Hidden Burden of Disease and Treatment Experiences of Patients with Essential Tremor: A Retrospective Claims Data Analysis

INTRODUCTION

Essential tremor (ET) affects approximately 7 million people in the USA, yet public recognition of the disease and its impact remain low.

METHODS

A retrospective observational study examined US claims data from 2015 to 2019 using the Compile database. ET diagnoses were captured using longitudinal data from 2015 to 2019 and for the year 2019, with diagnosis estimates extrapolated to the general US population. Confirmed ET was identified by an ET diagnosis code with at least two relevant prescriptions or by two diagnosis codes for ET and unspecified tremor at least 90 days apart. Comorbidity and treatment use data were extracted, and medication compliance and 2-year treatment persistence were assessed as measures of treatment adherence.

RESULTS

A total of 1,336,183 patients with ET diagnoses codes were identified from 2015 through 2019, corresponding to 2,226,971 projected US diagnoses. In 2019, 128,263 patients had a confirmed ET diagnosis, corresponding to 213,772 projected US confirmed diagnoses. Of these, 96% had at least one comorbidity, and 64% received at least one pharmacologic treatment. Propranolol (24%) and primidone (20%) comprised the most common ET prescriptions. Two-year medication discontinuation rates were approximately 40%.

CONCLUSION

Our findings revealed that 1 million people were diagnosed and sought treatment for ET in the USA from 2015 to 2019. Projected population estimates of approximately 2 million people diagnosed suggest a further 1 million remain untreated. Our findings highlight the complexity of patient care in ET, complicated by delayed diagnoses, multiple comorbidities, and lack of effective and tolerable therapies that can mitigate treatment adherence limitations.

The Pathophysiology and Treatment of Essential Tremor: The Role of Adenosine and Dopamine Receptors in Animal Models

Essential tremor (ET) is one of the most common neurological disorders that often affects people in the prime of their lives, leading to a significant reduction in their quality of life, gradually making them unable to independently perform the simplest activities. Here we show that current ET pharmacotherapy often does not sufficiently alleviate disease symptoms and is completely ineffective in more than 30% of patients. At present, deep brain stimulation of the motor thalamus is the most effective ET treatment. However, like any brain surgery, it can cause many undesirable side effects; thus, it is only performed in patients with an advanced disease who are not responsive to drugs. Therefore, it seems extremely important to look for new strategies for treating ET. The purpose of this review is to summarize the current knowledge on the pathomechanism of ET based on studies in animal models of the disease, as well as to present and discuss the results of research available to date on various substances affecting dopamine (mainly D3) or adenosine A1 receptors, which, due to their ability to modulate harmaline-induced tremor, may provide the basis for the development of new potential therapies for ET in the future.

Shuddering attacks: A benign phenomenon in children

QUESTION

A 2-year-old child was recently brought into my office for repeated episodes of neck stiffening and shivering movements of the shoulders and arms. The episodes last 4 to 5 seconds and occur more than 10 times per day, with no apparent pattern except increased frequency at mealtime. Although there has never been loss of consciousness, the parent was worried that these were seizures. The child was diagnosed by a neurologist as having shuddering attacks. Should I start antiepileptic medications for this child?

ANSWER

Shuddering attacks are involuntary movements of the head and upper extremities that occur during normal activities and do not impair consciousness. Normal neurologic examination findings and normal electroencephalogram tracing will confirm that this child has shuddering attacks, a benign phenomenon that requires no further investigation or medical therapy. The condition is of unknown cause but is distinct from epilepsy and neither warrants nor responds to antiepileptic medications. Parents can be reassured that attacks will decrease in frequency and will spontaneously remit with age.

Tolerability and Efficacy of Customized IncobotulinumtoxinA Injections for Essential Tremor: A Randomized, Double-Blind, Placebo-Controlled Study

In this first, double-blind, randomized, placebo-controlled exploratory trial, we evaluate the efficacy and safety of incobotulinumtoxinA and feasibility of using kinematic tremor assessment to aid in the planning of muscle selection in a multicenter setting. Reproducibility of the planning technology to other clinical sites was explored. In this trial (NCT02207946), patients with upper-limb essential tremor (ET) were randomized 2:1 to a single treatment cycle of incobotulinumtoxinA or placebo. A tremor kinematic analytics investigational device was used to define a customized muscle set for injection, related to the pattern of the wrist, forearm, elbow, and shoulder tremor for each patient, and the incobotulinumtoxinA dose per muscle (total ≤ 200 U). Fahn–Tolosa–Marin (FTM) Part B motor performance score, Global Impression of Change Scale (GICS), and kinematic analysis-based efficacy evaluations were assessed. Thirty patients were randomized (incobotulinumtoxinA, n = 19; placebo, n = 11). FTM motor performance scores showed greater improvement with incobotulinumtoxinA versus placebo at Week 4 (p= 0.003) and Week 8 (p= 0.031). The physician-rated GICS score indicated improvement with incobotulinumtoxinA versus placebo at Week 4 (p < 0.05). IncobotulinumtoxinA also decreased accelerometric hand-tremor amplitude versus placebo from baseline to Week 4 (p= 0.004) and Week 8 (p < 0.001), with persistent tremor reduction up to 24 weeks post-injection. IncobotulinumtoxinA produced a slight and transient reduction of maximal grip strength versus placebo; two patients reported localized finger muscle weakness. Customized incobotulinumtoxinA injections decreased tremor severity and improved hand motor function in patients with upper-limb ET after a single injection cycle, with a favorable tolerability profile. The study showed that tremor kinematic analytics technology could be successfully scaled for use in other clinical sites.

Brain Metabolic Changes with Longitudinal Transcutaneous Afferent Patterned Stimulation in Essential Tremor Subjects

Background

Non-invasive peripheral nerve stimulation, also referred to as transcutaneous afferent patterned stimulation (TAPS), reduces hand tremor in essential tremor (ET) subjects. However, the mechanism of action of TAPS is unknown. Here, we investigated changes in brain metabolism over three months of TAPS use in ET subjects.

Methods

This was an interventional, open label, single group study enrolling 5 ET subjects. They received 40 minutes of TAPS treatment twice daily for 90 days. Brain metabolic activity and tremor severity were measured using 18F-fluorodeoxyglucose (FDG) PET/CT, and the Tremor Research Group Essential Tremor Rating Assessment Scale (TETRAS), respectively, at baseline and after 90 days. Tremor power and frequency was measured before and after all TAPS sessions using an onboard three-axis accelerometer.

Results

FDG PET/CT revealed areas of hypermetabolism in ipsilateral cerebellar hemisphere and hypometabolism in contralateral cerebellar hemisphere following 90 days of TAPS treatment, compared to day one (uncorrected p value <0.05). Paired pre-post kinematic measurements over 90 days showed significantly decreased tremor power (p < 0.0001) but no change in tremor frequency. The TETRAS score on day 1 decreased from 6.5 ± 2.5 to 4.1 ± 1.8 following TAPS (p = 0.05). The pre-post TETRAS scores on day 90: 4.9 ± 1.5 and 4.1± 1 were lower than pre-TAPS TETRAS score on day 1 (p = 0.14 and 0.05, respectively).

Conclusions

Our results suggest that longitudinal TAPS of the median and radial nerves modulates brain metabolism in areas instrumental to motor coordination and implicated in ET. Clinically, TAPS reduced tremor power, but had no effect on tremor frequency. This study paves the way for comprehensive studies in larger cohorts to further elucidate the mechanism of TAPS.

Highlights

Non-invasive peripheral nerve stimulation, also referred to as transcutaneous afferent patterned stimulation (TAPS), reduces hand tremor in essential tremor subjects. Longitudinal TAPS therapy alters cerebellar metabolism, which can be a cause or consequence of tremor reduction. Cerebellar-premotor region connectivity may play a role in the anti-tremor effects of TAPS.

Transcutaneous Afferent Patterned Stimulation Therapy Reduces Hand Tremor for One Hour in Essential Tremor Patients

Essential tremor (ET) patients often experience hand tremor that impairs daily activities. Non-invasive electrical stimulation of median and radial nerves in the wrist using a recently developed therapy called transcutaneous afferent patterned stimulation (TAPS) has been shown to provide symptomatic tremor relief in ET patients and improve patients’ ability to perform functional tasks, but the duration of tremor reduction is unknown. In this single-arm, open-label study, fifteen ET patients performed four hand tremor-specific tasks (postural hold, spiral drawing, finger-to-nose reach, and pouring) from the Fahn-Tolosa-Marin Clinical Rating Scale (FTM-CRS) prior to, during, and 0, 30, and 60 min following TAPS. At each time point, tremor severity was visually rated according to the FTM-CRS and simultaneously measured by wrist-worn accelerometers. The duration of tremor reduction was assessed using (1) improvement in the mean FTM-CRS score across all four tasks relative to baseline, and (2) reduction in accelerometer-measured tremor power relative to baseline for each task. Patients were labeled as having at least 60 min of therapeutic benefit from TAPS with respect to each specified metric if all three (i.e., 0, 30, and 60 min) post-therapy measurements were better than that metric’s baseline value. The mean FTM-CRS scores improved for at least 60 min beyond the end of TAPS for 80% (12 of 15, p = 4.6e–9) of patients. Similarly, for each assessed task, tremor power improved for at least 60 min beyond the end of TAPS for over 70% of patients. The postural hold task had the largest reduction in tremor power (median 5.9-fold peak reduction in tremor power) and had at least 60 min of improvement relative to baseline beyond the end of TAPS therapy for 73% (11 of 15, p = 9.8e–8) of patients. Clinical ratings of tremor severity were correlated to simultaneously recorded accelerometer-measured tremor power (r = 0.33–0.76 across the four tasks), suggesting tremor power is a valid, objective tremor assessment metric that can be used to track tremor symptoms outside the clinic. These results suggest TAPS can provide reductions in upper limb tremor symptoms for at least 1 h post-therapy in some patients, which may improve patients’ ability to perform tasks of daily living.

Prospective Home-use Study on Non-invasive Neuromodulation Therapy for Essential Tremor

Highlights

This prospective study is one of the largest clinical trials in essential tremor to date. Study findings suggest that individualized non-invasive neuromodulation therapy used repeatedly at home over three months results in safe and effective hand tremor reduction and improves quality of life for many essential tremor patients.

Background

Two previous randomized, controlled, single-session trials demonstrated efficacy of non-invasive neuromodulation therapy targeting the median and radial nerves for reducing hand tremor. This current study evaluated efficacy and safety of the therapy over three months of repeated home use.

Methods

This was a prospective, open-label, post-clearance, single-arm study with 263 patients enrolled across 26 sites. Patients were instructed to use the therapy twice daily for three months. Pre-specified co-primary endpoints were improvements on clinician-rated Tremor Research Group Essential Tremor Rating Assessment Scale (TETRAS) and patient-rated Bain & Findley Activities of Daily Living (BF-ADL) dominant hand scores. Other endpoints included improvement in the tremor power detected by an accelerometer on the therapeutic device, Clinical and Patient Global Impression scores (CGI-I, PGI-I), and Quality of Life in Essential Tremor (QUEST) survey.

Results

205 patients completed the study. The co-primary endpoints were met (p≪0.0001), with 62% (TETRAS) and 68% (BF-ADL) of 'severe' or 'moderate' patients improving to 'mild' or 'slight'. Clinicians (CGI-I) reported improvement in 68% of patients, 60% (PGI-I) of patients reported improvement, and QUEST improved (p = 0.0019). Wrist-worn accelerometer recordings before and after 21,806 therapy sessions showed that 92% of patients improved, and 54% of patients experienced ≥50% improvement in tremor power. Device-related adverse events (e.g., wrist discomfort, skin irritation, pain) occurred in 18% of patients. No device-related serious adverse events were reported.

Discussion

This study suggests that non-invasive neuromodulation therapy used repeatedly at home over three months results in safe and effective hand tremor reduction in many essential tremor patients.

Injury of the dentato-rubro-thalamic tract in a patient with intentional tremor after mild traumatic brain injury: a case report

OBJECTIVES

We imaged the dentato-rubro-thalamic tract (DRTT) and cortico-ponto-cerebellar tract (CPCT) using diffusion tensor tractography (DTT) to evaluate the cortico-cerebellar-cortical circuit in a patient with tremor in both hands after mild TBI. We found bilateral DRTT injury in the DTT.

METHOD

A 50-year-old male presented with action tremor in both hands 1 week after mild TBI. One month before the visit, the patient had a head injury from a fall on a bus. The patient lost consciousness for 1 min and experienced post-traumatic amnesia for approximately 5 min after the accident. His Glasgow Coma Scale score was 15. The action tremor presented with a frequency of 3 Hz in both hands. No specific lesion was observed with a conventional brain MRI.

RESULTS

DTT, performed 1.5 months after TBI, showed that the right DRTT was not reconstructed and the left DRTT had thinned. However, CPCT integrity was well-preserved in both hemispheres. The tremor disappeared after oral treatment with 30 mg/day indenol. The patient's tremor would have been caused by disruption of the bilateral DRTT following mild TBI.

CONCLUSION

DRTT and CPCT analysis using DTT would be useful for diagnosing abnormal movement problems, including tremor and ataxia, in patients following mild TBI.

Population Pharmacokinetic Analysis of Bisoprolol in Patients With Acute Coronary Syndrome

To date, many questions about the extent and cause of pharmacokinetic (PK) variability of even the most widely studied and prescribed β1-adrenergic receptor blockers, such as metoprolol and bisoprolol, remain unanswered. Given that there are still no published population pharmacokinetic (PopPK) analyses of bisoprolol in routinely treated patients with acute coronary syndrome (ACS), the aim of this study was to determine its PK variability in 71 Serbian patients with ACS. PopPK analysis was conducted using a nonlinear mixed-effects model (NONMEM), version 7.3.0 (Icon Development Solutions). In each patient, the same formulation of bisoprolol was administered once or twice daily at a total daily dose of 0.625-7.5 mg. We separately assessed the effects of 31 covariates on the PKs of bisoprolol, and our results indicated that only 2 covariates could have possible influence on the variability of the clearance of bisoprolol: the mean daily dose of the drug and smoking habits of patients. These findings suggest that possible autoinduction of drug metabolism by higher total daily doses and induction of cytochrome P450 isoform 3A4 (CYP3A4) by cigarette smoke in liver could be the potential causes of increased total clearance of bisoprolol in patients with ACS.

Oral propranolol for treatment of the subgroups of essential tremor: a systematic review and meta-analysis protocol

INTRODUCTION

Essential tremor (ET), a tremor disorder, is one of the most common movement disorders. Only oral drugs (propranolol, primidone, topiramate, etc）are still the first-line treatment recommended by the Food and Drug Administration. Propranolol is thought to potentially reduce upper limb action tremor. However, it has a poor effect on axial tremor symptoms, such as essential head tremor and voice tremor. Studies have shown that tremor severity develops over time, possibly producing other clinical tremors and neurological soft signs (such as memory loss, gait abnormalities, balance disorders, etc), which further increases the difficulty of treating tremors. However, some recent studies provide emerging evidence for oral propranolol on subgroups of ET, which is based on the anatomical distribution of ET (lower extremities, head, sound, tongue, etc). This systematic review aims to synthesise these new data to improve the efficacy of propranolol in ET subgroups.

METHODS AND ANALYSIS

We will search for randomised controlled trials from the PubMed, MEDLINE, EMBASE, Cochrane Library, UptoDate and PEDro databases from inception to June 2019. All data will be extracted independently by two reviewers and compared at the end of the review. The two reviewers will screen the study quality, and the Cochrane Collaboration's tool in Review Manager (RevMan) V.5.3.3 will be used to evaluate risk of bias. Our primary outcome will be the functional disability component related to tremors, as measured by the Fahn-Tolosa-Marin Tremor Rating Scale subscales B and C. Secondary outcomes will include severity of tremors and quality of life. Narrative and meta-analytical syntheses are planned.

ETHICS AND DISSEMINATION

Published aggregated data will be used in this review analysis and therefore no ethical approval is required. The results will be published in peer-reviewed journals, and proliferation activities will include diverse social stakeholders, non-academic groups and patients.

PROSPERO REGISTRATION NUMBER

CRD42018112580.

[Essential tremor: genetic update]

Essential tremor (ET) is a neurological movement disorder characterised by bilateral limb kinetic/postural tremor, with or without tremor in other body parts including head, voice and lower limbs. Since no causative genes for ET have been identified, it is likely that the disorder occurs as a result of complex genetic factors interacting with various cellular and environmental factors that can result in abnormal function of circuitry involving the cerebello-thalamo-cortical pathway. Genetic analyses have uncovered at least 14 loci and 11 genes that are related to ET, as well as various risk or protective genetic factors. Limitations in ET genetic analyses include inconsistent disease definition, small sample size, varied ethnic backgrounds and many other factors that may contribute to paucity of relevant genetic data in ET. Genetic analyses, coupled with functional and animal studies, have led to better insights into possible pathogenic mechanisms underlying ET. These genetic studies may guide the future development of genetic testing and counselling, and specific, pathogenesis-targeted, therapeutic strategies.

A Phase 2, Randomized, Double-Blind, Placebo-Controlled Trial of CX-8998, a Selective Modulator of the T-Type Calcium Channel in Inadequately Treated Moderate to Severe Essential Tremor: T-CALM Study Design and Methodology for Efficacy Endpoint and Digital Biomarker Selection

Background: Essential tremor (ET) is a common, progressive neurological syndrome with bilateral upper-limb dysfunction of at least 3-year duration, with or without tremor in other body locations. This disorder has a negative impact on daily function and quality of life. A single oral therapy has been approved by FDA for ET. Off-label pharmacotherapies have inadequate efficacy and poor tolerability with high rates of patient dissatisfaction and discontinuation. Safe and efficacious pharmacotherapies are urgently needed to decrease tremor and improve daily living. T-CALM (Tremor-CAv3 modulation) protocol is designed to assess safety and efficacy of CX-8998, a selective modulator of the T-type calcium channel, for ET therapy.

Methods/Design: T-CALM is a phase 2, proof of concept, randomized, double-blind, placebo-controlled trial. Titrated doses of CX-8998 to 10 mg BID or placebo will be administered for 28 days to moderate to severe ET patients who are inadequately treated with existing therapies. The primary endpoint will be change from baseline to day 28 of The Essential Tremor Rating Assessment Performance Subscale (TETRAS-PS). Secondary efficacy endpoints for clinician and patient perception of daily function will include TETRAS Activity of Daily Living (ADL), Quality of Life in Essential Tremor Questionnaire (QUEST), Clinical Global Impression-Improvement (CGI-I), Patient Global Impression of Change (PGIC), and Goal Attainment Scale (GAS). Kinesia One, Kinesia 360, and iMotor will biometrically evaluate motor function and tremor amplitude. Safety will be assessed by adverse events, physical and neurological exams and laboratory tests. Sample size of 43 patients per group is estimated to have 90% power to detect a 5.5-point difference between CX-8998 and placebo for TETRAS-PS. Efficacy analyses will be performed with covariance (ANCOVA) and 2-sided test at 0.05 significance level.

Discussion: T-CALM has a unique design with physician rating scales, patient-focused questionnaires and scales and objective motor measurements to assess clinically meaningful and congruent efficacy. Patient perception of ET debilitation and therapy with CX-8998 will be key findings. Overall goal of T-CALM is generation of safety and efficacy data to support a go, no-go decision to further develop CX-8998 for ET. Design of T-CALM may guide future clinical studies of ET pharmacotherapies.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT03101241

Clinical management of Wilson disease

The availability of effective therapies distinguishes Wilson disease (WD) from other inherited neurometabolic diseases. The cause of hepatic, neurologic or psychiatric symptoms is copper overload and subsequent copper toxicity. Diagnosed WD patients require life-long pharmacologic therapy that is focused on reversal of copper overload with maintenance of a long-term negative copper balance. This is associated with the rapid control of free or non-ceruloplasmin bound copper that is mostly responsible for acute cytotoxic effects. Currently available therapies can be divided into chelators and zinc salts. They have different mechanisms of action and the onset of efficacy that influences their selection in acute and chronic stages of therapy. We review the use of D-penicillamine and trientine for chelation therapies, including the required monitoring of therapy for its efficacy and possible overtreatment with iatrogenic copper deficiency. Additionally, the use of zinc salts is also discussed, including a possibility of its use for the initial therapy in an acute stage of the disease. Supportive and symptomatic therapies for liver failure and neuropsychiatric symptoms are also reviewed.

Propranolol: A 50-Year Historical Perspective

Propranolol is a beta-adrenergic receptor antagonist that was developed by the British scientist Sir James Black primarily for the treatment of angina pectoris, more than 50 years ago. It was not long before several other cardiovascular as well as noncardiovascular therapeutic uses of propranolol were discovered. Propranolol soon became a powerful tool for physicians in the treatment of numerous conditions such as hypertension, cardiac arrhythmias, myocardial infarction, migraine, portal hypertension, anxiety, essential tremors, hyperthyroidism, and pheochromocytoma. Owing to its action at multiple receptor sites, propranolol exerts several central and peripheral effects and is therefore useful in various conditions. Right from reduction in postmyocardial mortality to control of anxiety in performers, propranolol plays an important role in a plethora of medical conditions. Interestingly, even today, newer indications of this age-old drug are being discovered. Moreover, propranolol treatment has been found to be cost-effective when compared to other corresponding treatment options for individual indications. In this article, we attempt to recount the journey of propranolol right from its inception to the present day.

Transitioning from Unilateral to Bilateral Upper Limb Tremor Therapy for Parkinson's Disease and Essential Tremor Using Botulinum Toxin: Case Series

Botulinum toxin type A (BoNT-A) injections guided by kinematic analysis for unilateral upper limb essential tremor (ET) and Parkinson’s disease (PD) tremor therapy has demonstrated efficacy, improvements in quality of life (QoL) and arm functionality. In this open-label pilot trial, 5 ET and 2 PD participants decided to switch from receiving long-term unilateral arm treatment to now bilateral BoNT-A arm therapy in their other tremulous arm which worsened over time. Injection patterns were based on kinematic analysis. Efficacy endpoints including kinematic analysis, Fahn-Tolosa-Marin tremor rating scale, QoL questionnaire, and maximal grip strength were collected over 2 treatments and 2 follow-up visits totaling 18-weeks. BoNT-A decreased wrist tremor amplitude by 84.6% and 89.6% 6-weeks following the 1st injection in the newly-treated limb in ET and PD participants, respectively. PD participants started with worse QoL but demonstrated an additional improvement in QoL by 29.9% for switching to bilateral treatment, whereas ET participants did not. Left and right arm tremor also did not share commonalities in severity or dose. This preliminary finding suggests trends for transitioning to bilateral therapy and warrants further studies to evaluate efficacy of bilateral tremor BoNT-A therapy in a larger cohort of PD and ET patients.

White matter measures correlate with essential tremor severity-A pilot diffusion tensor imaging study

BACKGROUND

An evolving pathophysiological concept of essential tremor (ET) points to diffuse brain network involvement, which emphasizes the need to investigate white matter (WM) changes associated with motor symptoms of ET.

OBJECTIVES

To investigate ET-related WM changes and WM correlates of tremor severity using tremor clinical rating scales and accelerometry.

METHODS

Tract-based spatial statistics (TBSS) approach was utilized to compare 3 Tesla diffusion tensor imaging (DTI) data from 12 ET patients and 10 age- and gender-matched healthy individuals. Clinical scales, tremor frequency and amplitude as measured by accelerometry were correlated with DTI data.

RESULTS

ET patients demonstrated mean (MD) and radial diffusivity (RD) abnormalities in tracts involved in primary and associative motor functions such as bilateral corticospinal tracts, the superior longitudinal fascicles, and the corpus callosum but also in nonmotor regions including the inferior fronto-occipital and longitudinal fascicles, cingulum bundles, anterior thalamic radiations, and uncinate fascicles. A combined tremor frequency and amplitude score correlated with RD and MD in extensive WM areas, which partially overlapped the regions that were associated with tremor frequency. No significant relationship was found between DTI measures and clinical rating scales scores.

CONCLUSIONS

The results show that ET-related diffusion WM changes and their correlates with tremor severity are preferentially located in the primary and associative motor areas. In contrast, a relationship between WM was not detected with clinical rating scales. Accelerometry parameters may, therefore, serve as a potentially useful clinical measures that relate to WM deficits in ET.

The Role of the Anesthesiologist during Magnetic Resonance-Guided Focused Ultrasound Thalamotomy for Tremor: A Single-Center Experience

Ablative incisionless neurosurgery has become possible through advances in focused ultrasound and magnetic resonance imaging (MRI). The great advantage of MRI-guided focused ultrasound (MRgFUS) is that the ablation is performed through an intact skull without surgery. Here, we review the new modality of MRgFUS for treating tremor and enlighten the role of the anesthesiologist in the unique procedural setting of the MRI suite. During the MRgFUS process, the patients should be awake and are required to cooperate with the medical staff to allow assessment of tremor reduction and potential occurrence of adverse effects. In addition, the patient's head is immobilized inside the MRI tunnel for hours. This combination presents major challenges for the attending anesthesiologist, who is required to try to prevent pain and nausea and when present, to treat these symptoms. Anxiety, vertigo, and vomiting may occur during treatment and require urgent treatment. Here, we review the literature available on anesthetic management during the procedure and our own experience and provide recommendations based on our collected knowledge.

Emerging strategies in the management of essential tremor

Currently available therapies for essential tremor (ET) provide sufficient control only for less than a half of patients and many unmet needs exist. This is in part due to the empiric nature of existing treatment options and persisting uncertainties about the pathogenesis of ET. The emerging concept of ET as a possible neurodegenerative disorder, better understanding of associated biochemical changes, including alterations in the γ-aminobutyric acid (GABA)-ergic system and gap junctions, and the identification of the role of the leucine-rich repeat and immunoglobulin-like domain-containing 1 (LINGO-1) gene in ET pathogenesis suggest new avenues for more targeted therapies. Here we review the most promising new approaches to treating ET, including allosteric modulation of GABA receptors and modifications of the LINGO-1 pathway. Medically refractory tremor can be successfully treated by high-frequency deep brain stimulation (DBS) of the ventral intermediate nucleus, but surgical therapies are also fraught with limitations due to adverse effects of stimulation and the loss of therapeutic response. The selection of additional thalamic and extrathalamic targets for electrode placements and the development of a closed-loop DBS system enabling automatic adjustment of stimulation parameters in response to changes in electrophysiologic brain activity are also reviewed. Tremor cancellation methods using exoskeleton and external hand-held devices are also briefly discussed.

Delayed regaining of gait ability in a patient with brain injury: A case report

BACKGROUND

Little is known about delay in regaining gait ability at a chronic stage after brain injury. In this study, we report on a single patient who regained the gait ability during 2 months of intensive rehabilitation starting 2 years after a brain injury.

METHODS AND RESULTS

A 40-year-old male patient diagnosed with viral encephalitis underwent comprehensive rehabilitation until 2 years after onset. However, he could not even sit independently and presented with severe physical deconditioning and severe ataxia. To understand his neurological state, 4 neural tracts related to gait function were reconstructed, and based on the state of these neural tracts, we decided that the patient had the neurological potential to walk independently. Therefore, we assumed that the main reasons for gait inability in this patient were severe physical deconditioning and truncal ataxia. Consequently, the patient underwent the following intensive rehabilitative therapy: administration of drugs for control of ataxia (topiramate, clonazepam, and propranolol) and movement therapy for physical conditioning and gait training. As a result, after 2 months of rehabilitation, he was able to walk independently on an even floor, with improvement of severe physical deconditioning and truncal ataxia.

CONCLUSION

We described the rehabilitation program in a single patient who regained the gait ability during 2 months of intensive rehabilitation starting 2 years after a brain injury.

Movement Disorders: A Brief Guide in Medication Management

Movement disorders can be challenging to manage and often use a specific set of medications. Because it is a complex and broad field within neurology, many providers are unfamiliar with the classes of medications. This paper details medications used for specific conditions, explains why these medications are helpful, and shares pearls and pitfalls related to each agent, focusing on parameters such as dose titration, side effect profiles, and specific drug-drug interactions and challenges. We focus on the most commonly encountered movement disorders, including essential tremor, Parkinson's disease, rapid eye movement sleep behavior disorder, and restless leg syndrome.

Bilateral cerebellar activation in unilaterally challenged essential tremor

Background

Essential tremor (ET) is one of the most common hyperkinetic movement disorders. Previous research into the pathophysiology of ET suggested underlying cerebellar abnormalities.

Objective

In this study, we added electromyography as an index of tremor intensity to functional Magnetic Resonance Imaging (EMG-fMRI) to study a group of ET patients selected according to strict criteria to achieve maximal homogeneity. With this approach we expected to improve upon the localization of the bilateral cerebellar abnormalities found in earlier fMRI studies.

Methods

We included 21 propranolol sensitive patients, who were not using other tremor medication, with a definite diagnosis of ET defined by the Tremor Investigation Group. Simultaneous EMG-fMRI recordings were performed while patients were off tremor medication. Patients performed unilateral right hand and arm extension, inducing tremor, alternated with relaxation (rest). Twenty-one healthy, age- and sex-matched participants mimicked tremor during right arm extension. EMG power variability at the individual tremor frequency as a measure of tremor intensity variability was used as a regressor, mathematically independent of the block regressor, in the general linear model used for fMRI analysis, to find specific tremor-related activations.

Results

Block-related activations were found in the classical upper-limb motor network, both for ET patients and healthy participants in motor, premotor and supplementary motor areas. In ET patients, we found tremor-related activations bilaterally in the cerebellum: in left lobules V, VI, VIIb and IX and in right lobules V, VI, VIIIa and b, and in the brainstem. In healthy controls we found simulated tremor-related activations in right cerebellar lobule V.

Conclusions

Our results expand on previous findings of bilateral cerebellar involvement in ET. We have identified specific areas in the bilateral somatomotor regions of the cerebellum: lobules V, VI and VIII.