Effects of low-frequency repetitive transcranial magnetic stimulation in adductor laryngeal dystonia: a safety, feasibility, and pilot study

Volitional and Non-volitional Devices Used in Voice Therapy and Training: A Scoping Review-Part A

OBJECTIVE

To map the volitional and non-volitional devices used by speech and language pathologists (SLPs) in voice training and therapy and characterize their use in research on voice interventions.

METHODS

This scoping review is the first part of a larger study. The electronic search was carried out by mapping the references in PubMed/Medline, LILACS/BVS, Scopus, Web of Science, EMBASE, and the Cochrane Library, and the manual search was carried out in the grey literature. Two blind independent reviewers selected and extracted data; divergences were solved by consensus. The data extracted in this part of the study were the authorship and year of publication, country, study design, sample characteristics, intervention modality, ingredient, target, mechanism of action, dosage, and outcome measures. They were addressed with descriptive analysis.

RESULTS

Publications that use devices as ingredients are mostly from the last two decades, mainly carried out in the United States of America and Brazil, in adults of both sexes with behavioral dysphonia. Forty-two types of devices were used, many of them with similar approaches but different nomenclatures. Most devices were used voluntarily, focusing on vocal function, and aiming to increase source and filter interaction. Most studies used silicone tubes. The most reported technical specification to apply the ingredient was surface electrodes on the neck. Device dosage was time-controlled, and the most used outcomes were self-assessment and acoustic analysis.

CONCLUSION

Devices are currently used as ingredients in vocal interventions, with a greater focus on increasing the source and filter interaction, associated with silicone tubes (the most used devices in these studies), which have been dosed with performance time. Outcomes were measured with self-assessment instruments.

Exploring Neurophysiological Mechanisms and Treatment Efficacies in Laryngeal Dystonia: A Transcranial Magnetic Stimulation Approach

Laryngeal dystonia (LD), known or termed as spasmodic dysphonia, is a rare movement disorder with an unknown cause affecting the intrinsic laryngeal muscles. Neurophysiological studies point to perturbed inhibitory processes, while conventional genetic studies reveal fragments of genetic architecture in LD. The study's aims are to (1) describe transcranial magnetic stimulation (TMS) methodology for studying the functional integrity of the corticospinal tract by stimulating the primary motor cortex (M1) for laryngeal muscle representation and recording motor evoked potentials (MEPs) from laryngeal muscles; (2) evaluate the results of TMS studies investigating the cortical silent period (cSP) in LD; and (3) present the standard treatments of LD, as well as the results of new theoretical views and treatment approaches like repetitive TMS and laryngeal vibration over the laryngeal muscles as the recent research attempts in treatment of LD. Neurophysiological findings point to a shortened duration of cSP in adductor LD and altered cSP duration in abductor LD individuals. Future TMS studies could further investigate the role of cSP in relation to standard laryngological measures and treatment options. A better understanding of the neurophysiological mechanisms might give new perspectives for the treatment of LD.

Machine Learning Assessment of Spasmodic Dysphonia Based on Acoustical and Perceptual Parameters

Adductor spasmodic dysphonia is a type of adult-onset focal dystonia characterized by involuntary spasms of laryngeal muscles. This paper applied machine learning techniques for the severity assessment of spasmodic dysphonia. To this aim, 7 perceptual indices and 48 acoustical parameters were estimated from the Italian word /a’jwɔle/ emitted by 28 female patients, manually segmented from a standardized sentence and used as features in two classification experiments. Subjects were divided into three severity classes (mild, moderate, severe) on the basis of the G (grade) score of the GRB scale. The first aim was that of finding relationships between perceptual and objective measures with the Local Interpretable Model-Agnostic Explanations method. Then, the development of a diagnostic tool for adductor spasmodic dysphonia severity assessment was investigated. Reliable relationships between G; R (Roughness); B (Breathiness); Spasmodicity; and the acoustical parameters: voiced percentage, F2 median, and F1 median were found. After data scaling, Bayesian hyperparameter optimization, and leave-one-out cross-validation, a k-nearest neighbors model provided 89% accuracy in distinguishing patients among the three severity classes. The proposed methods highlighted the best acoustical parameters that could be used jointly with GRB indices to support the perceptual evaluation of spasmodic dysphonia and provide a tool to help severity assessment of spasmodic dysphonia.

Effects of non-invasive brain stimulation in dystonia: a systematic review and meta-analysis

Background

Deep brain stimulation is a highly effective treatment of dystonia but is invasive and associated with risks, such as intraoperative bleeding and infections. Previous research has used non-invasive brain stimulation (NIBS) in an attempt to alleviate symptoms of dystonia. The results of these studies, however, have been variable, leaving efficacy unclear.

Objectives

This study aimed to evaluate the effects of NIBS on symptoms of dystonia and determine whether methodological characteristics are associated with variability in effect size.

Methods

Web of Science, Embase, and MEDLINE Complete databases were searched for articles using any type of NIBS as an intervention in dystonia patients, with changes in dystonia symptoms the primary outcome of interest.

Results

Meta-analysis of 27 studies demonstrated a small effect size for NIBS in reducing symptoms of dystonia (random-effects Hedges' g = 0.21, p = .002). Differences in the type of NIBS, type of dystonia, and brain region stimulated had a significant effect on dystonia symptoms. Meta-regression revealed that 10 sessions of active stimulation and the application of concurrent motor training programs resulted in significantly larger mean effect sizes.

Conclusion

NIBS has yielded small improvements to dystonic symptoms, but effect sizes depended on methodological characteristics, with more sessions of stimulation producing a larger response. Future research should further investigate the application of NIBS parallel to motor training, in addition to providing a greater quantity of sessions, to help define optimal parameters for NIBS protocols in dystonia.

Registration

PROSPERO 2020, CRD42020175944.

Spectral Aggregate of the High-Passed Fundamental Frequency and Its Relationship to the Primary Acoustic Features of Adductor Laryngeal Dystonia

OBJECTIVE

Currently, no clinically feasible objective measures exist that are specific to the signs of adductor laryngeal dystonia (LD), deterring effective diagnosis and treatment. This project sought to establish concurrent validity of a new automated acoustic outcome measure, designed to be specific to adductor laryngeal dystonia (AdLD): the spectral aggregate of the high-passed fundamental frequency contour (SAHf o).

METHOD

Twenty speakers with AdLD read voiced phoneme-loaded (more symptomatic) and voiceless phoneme-loaded (less symptomatic) sentences. LD discontinuities (defined as phonatory breaks, frequency shifts, and creak), the acoustic ramifications of laryngeal spasms, were manually identified. The frequency content of the f o contour was examined as a function of time, and content above 1000 Hz was summed to automatically calculate SAHf o. Multiple linear regression analysis was applied to SAHf o based on LD discontinuities and sentence type (voiced or voiceless phoneme-loaded).

RESULTS

The regression model accounted for 41.1% of the variance in SAHf o. Both the LD discontinuities and sentence type were statistically related to SAHf o.

CONCLUSION

Results of this study provide evidence of concurrent validity. SAHf o is an automatic outcome measure specific to acoustic signs of AdLD that may be useful to track treatment progress.

The Patho-Neurophysiological Basis and Treatment of Focal Laryngeal Dystonia: A Narrative Review and Two Case Reports Applying TMS over the Laryngeal Motor Cortex

Focal laryngeal dystonia (LD) is a rare, idiopathic disease affecting the laryngeal musculature with an unknown cause and clinically presented as adductor LD or rarely as abductor LD. The most effective treatment options include the injection of botulinum toxin (BoNT) into the affected laryngeal muscle. The aim of this narrative review is to summarize the patho-neuro-physiological and genetic background of LD, as well as the standard recommended therapy (BoNT) and pharmacological treatment options, and to discuss possible treatment perspectives using neuro-modulation techniques such as repetitive transcranial magnetic stimulation (rTMS) and vibrotactile stimulation. The review will present two LD cases, patients with adductor and abductor LD, standard diagnostic procedure, treatments and achievement, and the results of cortical excitability mapping the primary motor cortex for the representation of the laryngeal muscles in the assessment of corticospinal and corticobulbar excitability.

Repetitive Transcranial Magnetic Stimulation of the Primary Motor Cortex beyond Motor Rehabilitation: A Review of the Current Evidence

Transcranial magnetic stimulation (TMS) has emerged as a novel technique to stimulate the human brain through the scalp. Over the years, identifying the optimal brain region and stimulation parameters has been a subject of debate in the literature on therapeutic uses of repetitive TMS (rTMS). Nevertheless, the primary motor cortex (M1) has been a conventional target for rTMS to treat motor symptoms, such as hemiplegia and spasticity, as it controls the voluntary movement of the body. However, with an expanding knowledge base of the M1 cortical and subcortical connections, M1-rTMS has shown a therapeutic efficacy that goes beyond the conventional motor rehabilitation to involve pain, headache, fatigue, dysphagia, speech and voice impairments, sleep disorders, cognitive dysfunction, disorders of consciousness, anxiety, depression, and bladder dysfunction. In this review, we summarize the latest evidence on using M1-rTMS to treat non-motor symptoms of diverse etiologies and discuss the potential mechanistic rationale behind the management of each of these symptoms.