Laryngeal Dystonia

Using a comprehensive approach of clinico-behavioral testing and neuroimaging, the researchers will examine the clinical effects of the extended-release formulation of sodium oxybate on voice symptoms in spasmodic dysphonia in an open-label, proof-of-concept, dose-finding study.

Laryngeal dystonia (LD) is a focal dystonia affecting laryngeal muscles, causing involuntary spasms that impair speech production. Recent research demonstrated that non-invasive vibrotactile stimulation (VTS) of the laryngeal area can provide acute symptom relief in up to 57% of patients, with improvements in voice quality and reductions in perceived speech effort lasting from minutes to several days. However, the neural mechanisms underlying this therapeutic effect and the factors determining individual treatment response remain incompletely understood. The objective is to evaluate the acute effects of VTS on voice and speech parameters in participants with LD while characterizing associated changes in brain resting-state networks using magnetic resonance imaging (MRI).

Laryngeal dystonia (LD) causes excessive vocal fold abduction (opening) or adduction (closing) leading to decreased voice quality, job prospects, self-worth and quality of life. Individuals with LD often experience episodic breathy voice, decreased ability to sustain vocal fold vibration, frequent pitch breaks and in some cases, vocal tremor. While neuroimaging investigations have uncovered both cortical organization and regional connectivity differences in structures in parietal, primary somatosensory and premotor cortices of those with LD, there remains a lack of understanding regarding how the brains of those with LD function to produce phonation and how these might differ from those without LD. Intervention options for people with LD are limited to general voice therapy techniques and Botulinum Toxin (Botox) injections to the posterior cricoarytenoid (PCA) and/or TA (thyroarytenoid) often bilaterally, to alleviate muscle spasms in the vocal folds. However, the effects of injections are short-lived, uncomfortable, and variable. To address this gap, the aim of this study is to investigate the effectiveness of repetitive transcranial magnetic stimulation (rTMS), a non-invasive neuromodulation technique, in assessing cortical excitability and inhibition of laryngeal musculature. Previous work conducted by the investigator has demonstrated decreased intracortical inhibition in those with adductor laryngeal dystonia (AdLD) compared to healthy controls. The investigators anticipate similar findings in individuals with with other forms of LD, where decreased cortical inhibition will likely be noted in the laryngeal motor cortex. Further, following low frequency (inhibitory) rTMS to the laryngeal motor brain area, it is anticipated that there will be a decrease in overactivation of the TA muscle. To test this hypothesis, a proof-of-concept, randomized study to down-regulate cortical motor signal to laryngeal muscles will be compared to those receiving an equal dose of sham rTMS. Previous research conducted by the investigator found that a single session of the proposed therapy produced positive phonatory changes in individuals with AdLD and justifies exploration in LD.

This project will apply transcranial direct current stimulation (tDCS) to multiple brain areas to evaluate the effects as a potential treatment for laryngeal dystonia (formerly spasmodic dysphonia).

The researchers will examine functional neural correlates that differentiate between laryngeal dystonia and voice tremor and contribute to disorder-specific pathophysiology using a cross-disciplinary approach of multimodal brain imaging.

The researchers will systematically evaluate current and novel clinical voice assessment tools and measures to elucidate distinct clinical phenotypes of those with laryngeal dystonia and voice tremor.

The goals of this project are 1) to determine the incidence of neurological voice disorders in patients with dystonia and essential tremor undergoing deep brain stimulation (DBS), 2) investigate the neuroimaging and intracranial neurophysiology correlates of voice dysfunction in these subjects, and subsequently 3) determine the effects of DBS on voice function.

The researchers will develop and evaluate the use of adaptive closed-loop brain-computer interface therapeutic intervention in laryngeal dystonia.

The contribution of genetic risk factors to the development of focal dystonias is evident. However, understanding of how variations in the causative gene expression lead to variations in brain abnormalities in different phenotypes of dystonia (e.g., familial, sporadic) remains limited. The research program of the investigators is set to determine the relationship between brain changes and genetic risk factors in laryngeal dystonia (or spasmodic dysphonia). The researchers use a novel approach of combined imaging genetics, next-generation DNA sequencing, and clinical-behavioral testing. The use of a cross-disciplinary approach as a tool for the discovery of the mediating neural mechanisms that bridge the gap from DNA sequence to the pathophysiology of dystonia holds a promise for the understanding of the mechanistic aspects of brain function affected by risk gene variants, which can be used reliably for the discovery of associated genes and neural integrity markers for this disorder. The expected outcome of this study may lead to better clinical management of this disorder, including its improved detection, accurate diagnosis, and assessment of the risk of developing dystonia in family members.

Deep Brain Stimulation (DBS) is a neurosurgical procedure used to treat tremors, and dystonia. This study will enroll people who have a form of focal dystonia that affects their vocal cords called Adductor Laryngeal dystonia (ADLD). Participants will undergo Deep Brain Stimulation surgery to treat laryngeal dystonia as part of their clinical care. Before surgery, as part of the study they will have specialized testing to study the movement of the vocal cords, as well as functional magnetic resonance imaging (fMRI). While in the operating room, researchers will examine brain waves to better understand how faulty brain firing patterns lead to dystonia. After surgery, and activation of the deep brain stimulator, participants will repeat speech testing and vocal cord imaging as well as magnetic resonance imaging (MRI).