Evidence for Standalone Voice Therapy in the Management of Spasmodic Dysphonia: A Systematic Review and Identification of Research Gaps

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Abstract

BACKGROUND: Spasmodic dysphonia is characterized by involuntary spasms of the laryngeal muscles occurring during vocal fold adduction or abduction; the underlying cause remains unknown. Management of spasmodic dysphonia ranges from surgical interventions and voice therapy to pharmacological injections into the laryngeal musculature; however, no currently available treatment provides a permanent cure. In routine practice, these patients often initially consult a voice or speech-language pathologist. Voice pathologists therefore require evidence-based research findings regarding the potential utility of initiating therapy alone versus early referral to a laryngologist, as well as identifying which types and severities of spasmodic dysphonia may benefit from standalone voice therapy. OBJECTIVE: To systematically evaluate the available evidence regarding standalone voice therapy as a treatment approach for individuals with spasmodic dysphonia and identify existing evidence gaps. STUDY DESIGN: Systematic review. METHODS ELIGIBILITY CRITERIA POPULATION: Studies involving children or adults diagnosed with all subtypes of spasmodic dysphonia (adductor, abductor, and mixed forms) through clinical and/or instrumental assessment were considered eligible for the study. Studies involving participants with an unconfirmed SD diagnosis, muscle tension dysphonia without SD, or structural/organic voice disorders unrelated to SD were excluded. Eligible study designs included randomized controlled trials, nonrandomized studies, cohort studies, before-and-after studies, and case series involving at least three participants. INTERVENTION: Studies involving patients undergoing standalone voice therapy, including behavioral voice therapy, resonant voice therapy, vocal function exercises, respiratory-phonatory coordination training, relaxation-based approaches, and compensatory voice strategies of any duration or frequency, were considered eligible. RISK OF BIAS: Risk of bias was planned using RoB 2 (randomized studies) and ROBINS-I (nonrandomized studies). This assessment was not performed due to the absence of included studies. SYNTHESIS OF RESULTS: A narrative synthesis was planned. Meta-analysis was not feasible due to the absence of eligible studies. RESULTS: A total of 29 records were identified through database searching and supplementary sources. All records were imported into Rayyan for screening. No duplicate records were removed. During title and abstract screening, 22 records were excluded as they did not meet the eligibility criteria. Seven articles were retrieved for full-text assessment. Following full-text review, all seven articles were excluded due to the inclusion of botulinum toxin as part of the intervention, absence of standalone voice therapy outcomes, or non-interventional study designs. Therefore, no studies met the inclusion criteria for qualitative or quantitative synthesis INTERPRETATION: This systematic review identified a critical evidence gap regarding standalone voice therapy for spasmodic dysphonia. The absence of eligible studies prevents conclusions regarding effectiveness, but highlights the need for rigorous prospective studies evaluating patient selection, intervention protocols, and clinically meaningful outcomes.

Abstract as published, via PubMed.