Effectiveness of Voice Therapy on Voice Quality and Function in Individuals with Unilateral Vocal Fold Paralysis: Systematic Review and Meta-Analysis.

BACKGROUND

Unilateral vocal fold paralysis (UVFP), characterized by immobility of one vocal fold, results from injuries of recurrent laryngeal nerves. Voice therapy is a conservative intervention aiming to address these symptoms, but standard protocols are lacking. In this study, we provided an updated review of voice therapy for UVFP over the past 3 years and analyzed the effect of voice therapy from the perspective of voice assessment recommended by the guidelines of the European Laryngological Society and the Union of the European Phoniatricians in 2023.

METHODS

Following preferred reporting items for systematic reviews and meta-analyses (PRISMA) 2020 statement, we searched the databases, including PubMed, Embase, Web of Science, the Cochrane Library, and SCOPUS, from their earliest records to December 1, 2023. Quality assessment utilized Cochrane Risk of Bias and Risk Of Bias In Non-randomized Studies of Interventions tools. Data extraction encompassed study design, participant characteristics, therapy protocols, and outcome measures, including subjective and objective assessments. We performed heterogeneity analysis by calculating the I statistic and meta-analysis by calculating the standardized difference of means and weighted mean differences.

RESULTS

Our systematic review and meta-analysis included 12 studies encompassing 459 patients. The review revealed a predominance of female participants across studies. Therapy protocols primarily included breathing control, laryngeal manipulation, and resonance training, often supplemented by home exercises. Outcome measures demonstrated significant improvements in subjective parameter: Voice Handicap Index ((standard mean difference) SMD = -1.51, P < 0.001), acoustic parameters: fundamental frequency (SMD = -0.38, P = 0.003), jitter (SMD = -0.97, P < 0.001), shimmer (SMD = -0.94, P < 0.001), and noise-to-harmonic ratio (SMD = -0.89, P < 0.001), and aerodynamic parameters: maximum phonation time (SMD = 1.29, P < 0.001), with early intervention yielding enhanced rate of complete glottal closure.

DISCUSSION

Two randomized controlled trials (RCTs) involved patients aware of their allocation to the treatment group, and the remaining 10 studies were retrospective, leading to bias from deviations in the intended intervention. Subjective and aerodynamic parameter inconsistency was observed, but after excluding studies with the onset of UVFP greater than 12 months, the heterogeneity of VHI scores decreased. The funnel plot was grossly symmetrical in the publication bias test. Significant improvements were noted in subjective, acoustic, and aerodynamic outcomes after intervention. Besides, there were commonalities in protocols, such as breathing control, laryngeal manipulation, and resonance training, often supplemented by home exercises.

SYSTEMATIC REVIEW REGISTRATION

This protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on March 28, 2024, registration number: CRD42024529750.