Spasmodic Dysphonia: A Review. Part 2: Characterization of Pathophysiology

Objective: The purpose of this review is to describe the recent advances in characterizing spasmodic dysphonia. Spasmodic dysphonia is a task-specific focal laryngeal dystonia characterized by irregular and uncontrolled voice breaks. The pathophysiology is poorly understood, and there are diagnostic difficulties. Data Sources: PubMed, Google Scholar, and Cochrane Library. Review Methods: The data sources were searched using the following search terms: (spasmodic dysphonia or laryngeal dystonia) and (etiology, aetiology, diagnosis, pathogenesis, or pathophysiology). Conclusion: The diagnosis of spasmodic dysphonia can be difficult due to the lack of a scientific consensus on diagnostic criteria and the fact that other voice disorders may present similarly. Confusion can arise between spasmodic dysphonia and muscle tension dysphonia. Spasmodic dysphonia symptoms are tied to particular speech sounds, whereas muscle tension dysphonia is not. With the advent of more widespread use of high-speed laryngoscopy and videokymography, measures of the disruptions in phonation and delays in the onset of vocal fold vibration after vocal fold closure can be quantified. Recent technological developments have expanded our understanding of the pathophysiology of spasmodic dysphonia. Implications for Practice: A 3-tiered approach, involving a questionnaire, followed by speech assessment and nasolaryngoscopy is the most widely accepted method for making the diagnosis in most cases. More experimental and invasive techniques such as electromyography and neuroimaging have been explored to further characterize spasmodic dysphonia and aid in diagnosing difficult cases.