Sodium Oxybate in Alcohol-Responsive Essential Tremor of Voice: An Open-Label Phase II Study

Beyond surgery: Repurposing anesthetics for treatment of central nervous system disorders

The development of new drugs is a complex, expensive, and time-consuming process, often fraught with a high likelihood of failure. Amid these challenges, drug repurposing, which identifies new therapeutic applications for already existing medications, offers a more economical and time-saving approach, particularly in the challenging field of neurological and psychiatric disorders. This narrative review explores both preclinical and clinical studies to examine the potential of anesthetics such as ketamine, nitrous oxide, isoflurane, sevoflurane, propofol, dexmedetomidine, and sodium oxybate in treating central nervous system disorders. Various research highlights the potential of anesthetics to provide rapid antidepressant effects, enhance learning and memory, improve synaptic plasticity, and offer neuroprotective benefits, demonstrating promise for treating depression, post-traumatic stress disorder, cognitive decline, traumatic brain injury, and neurodegenerative disorders. Anesthetics appear to alleviate symptoms in neurological conditions, likely by modulating GABAergic and glutamatergic pathways. However, challenges such as dose-dependent neurotoxicity, variability in preclinical and clinical outcomes, as well as environmental concerns remain significant issues. Future research is essential to optimize dosing strategies, ensure long-term safety, and gain a deeper understanding of the precise mechanisms of action. The concept of anesthetics' repurposing presents a unique solution to tackle the challenges in neurological and psychiatric therapy by providing a platform for the development of new and improved therapies.

Neuromodulation for Laryngeal Dystonia: A Systematic Review

OBJECTIVE

The aim of this study was to systematically review and evaluate neuromodulation therapies that are currently being explored/used in the treatment of laryngeal dystonia (LD).

METHODS

A systematic review of the literature was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines searching Embase, Medline, and Cochrane with the cover period January 1960-August 2024. The search strategy used was (("Laryngeal Dystonia" OR "Spasmodic Dysphonia") AND ("Neuromodulation" OR "Deep Brain Stimulation")). Articles were reviewed and screened based on the set inclusion and exclusion criteria. The Joanna Briggs Institute Critical Appraisal Checklists were used to assess the risk of bias in the included studies. Patient demographics and diagnosis, neuromodulation therapy used and its details, voice outcomes, and complications were extracted from each of the studies. A narrative review was subsequently synthesized.

RESULTS

Twelve studies met the selection criteria and were included. In total, 130 LD patients were identified with the following neuromodulation therapies being evaluated for their use in LD: vibro-tactile stimulation, laryngeal electrical stimulation, pharmacologic (sodium oxybate), repetitive transcranial magnetic stimulation, and deep brain stimulation (DBS). All included studies reported various degrees of improvement in patients' voice symptoms with the neuromodulation therapy used. No definitive conclusion could be drawn for their efficacy within the included studies consisting of six case reports, three proof-of-concept/pilot studies, and three phase I clinical trials that used a number of different voice outcome measures used to report treatment effects, and a general lack of long-term follow-up. No significant complications were reported for any of the neuromodulation therapies.

CONCLUSION

Most neuromodulation therapies being explored for LD are at a very early exploratory stage. Although more clinical trials are required, from the available evidence, sodium oxybate and DBS currently appear to have the most potential for translation into clinical practice.

Efficacy and Safety of Sodium Oxybate in Isolated Focal Laryngeal Dystonia: A Phase IIb Double-Blind Placebo-Controlled Cross-Over Randomized Clinical Trial

OBJECTIVE

To examine the efficacy and safety of sodium oxybate versus placebo in a phase IIb randomized double-blind placebo-controlled 2-period cross-over clinical trial in patients with isolated laryngeal dystonia (LD).

METHODS

The study was conducted from January 2018 to December 2021, pausing during the COVID-19 pandemic, at Massachusetts Eye and Ear in 106 patients with alcohol-responsive (EtOH+) and alcohol-non-responsive (EtOH-) LD (53 to receive 1.5g of sodium oxybate first, 53 to receive matching placebo first). The primary outcome was a change from baseline in LD symptom severity 40 minutes after drug intake. Safety was based on vital signs, cognitive function, suicidality, daytime sleepiness, and adverse events. Patients, investigators, and outcome assessors were masked to study procedures.

RESULTS

Compared to baseline, EtOH+ but not EtOH- patients had a statistically significant improvement in LD symptoms following sodium oxybate versus placebo (EtOH+: 98.75% confidence interval [CI] = 0.6-26.9; p = 0.008; EtOH-: 98.75% CI = -6.2 to 18.7; p = 0.42). Statistically significant minimum drug efficacy in EtOH+ patients was found at ≥16% symptom improvement (OR = 2.09; 98.75% CI = 0.75-5.80; p = 0.036), with an average of 40.81% benefits (98.75% CI = 34.7-48.6). Drug efficacy waned by 300 minutes after intake without a rebound. No changes were found in cognitive function, suicidality, or vital signs. Common adverse events included mild dizziness, nausea, and daytime sleepiness.

INTERPRETATION

Sodium oxybate showed clinically meaningful improvement of symptoms in EtOH+ LD patients, with acceptable tolerability. Sodium oxybate offers the first pathophysiologically relevant oral treatment for laryngeal dystonia. ANN NEUROL 2025;97:329-343.

Essential tremor - drug treatments present and future

INTRODUCTION

The main treatment options for essential tremor (ET), which is probably one of the most common movement disorders, have been propranolol and primidone, for many years. This review aims to synthesize therapeutic attempts with other drugs.

AREAS COVERED

We have reviewed the current state of the pharmacological treatment of ET, both in patients and in experimental models of this disease, with special emphasis on the data published in the last 5 years. Based on the results in experimental models of ET, proposals have been made for future alternative therapeutic options.

EXPERT OPINION

The use of drugs other than propranolol and primidone has not shown a greater degree of efficacy than these in the treatment of ET, although according to certain evidence-based guidelines topiramate and phenobarbital could be alternative drugs. The results on the effectiveness of other drugs have been variable. For patients with refractory ET, especially those with head tremor, local injections with botulinum toxin A may be useful. According to the results of various experimental models, T calcium channel blockers, modulators of GABAA receptors (GABAARs), GABAB receptors (GABABRs), and glutamatergic neurotransmission, and drugs that decrease the expression of LINGO-1 could be interesting options for the future, among others.

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

BACKGROUND

Tremor disorders remain as clinical diagnoses and the rate of misdiagnosis between the commonest non-parkinsonian tremors is relatively high.

OBJECTIVES

To compare the clinical features of Essential Tremor without other features (pure ET), ET plus soft dystonic signs (ET + DS), and tremor combined with dystonia (TwD).

METHODS

We compared the clinical features of patients with pure ET, ET + DS, and TwD enrolled in The ITAlian tremor Network (TITAN). Linear regression models were performed to determine factors associated with health status and quality of life.

RESULTS

Three-hundred-eighty-three patients were included. Sex distribution was significantly different between the groups with males being more represented in pure ET and females in TwD. The initial site of tremor was different between the groups with about 40% of TwD having head tremor and ET + DS unilateral upper limb tremor at onset. This pattern mirrored the distribution of overt dystonia and soft dystonic signs at examination. Sensory trick, task-specificity, and position-dependence were more common, but not exclusive, to TwD. Pure ET patients showed the lowest degree of alcohol responsiveness and ET + DS the highest. Midline tremor was more commonly encountered and more severe in TwD than in the other groups. Regression analyses demonstrated that tremor severity, sex, age, and to a lesser degree the variable "group", independently predicted health status and quality of life, suggesting the existence of other determinants beyond tremor.

CONCLUSIONS

Pure ET and TwD manifest with a phenotypic overlap, which calls for the identification of diagnostic biomarkers. ET + DS shared features with both syndromes, suggesting intra-group heterogeneity.