The Efficacy of the Manual Circumlaryngeal Therapy for Muscle Tension Dysphonia: A Systematic Review and Meta-analysis

Abstract

Objective: Muscle tension dysphonia (MTD) is the most common functional voice disorder. Behavioral voice therapy is the front-line treatment for MTD, and laryngeal manual therapy may be a part of this treatment. The objective of this study was to investigate the effect of manual circumlaryngeal therapy (MCT) on acoustic markers of voice quality (jitter, shimmer, and harmonics-to-noise ratio) and vocal function (fundamental frequency) through a systematic review with meta-analysis. Data Sources: Four databases were searched from inception to December 2022, and a manual search was performed. Review Methods: The PRISMA extension statement for reporting systematic reviews incorporating a meta-analysis of health care interventions was applied, and a random effects model was used for the meta-analyses. Results: We identified 6 eligible studies from 30 studies (without duplicates). The MCT approach was highly effective on acoustics with large effect sizes (Cohen's d > 0.8). Significant improvements were obtained in jitter in percent (mean difference of −.58; 95% CI −1.00 to 0.16), shimmer in percent (mean difference of −5.66; 95% CI −8.16 to 3.17), and harmonics-to-noise ratio in dB (mean difference of 4.65; 95% CI 1.90–7.41), with the latter two measurements continuing to be significantly improved by MCT when measurement variability is considered. Conclusion: The efficacy of MCT for MTD was confirmed in most clinical studies by assessing jitter, shimmer, and harmonics-to-noise ratio related to voice quality. The effects of MCT on the fundamental frequency changes could not be verified. Further contributions of high-quality randomized control trials are needed to support evidence-based practice in laryngology. Laryngoscope, 134:18–26, 2024.