Effects of Voice Therapy on Maximum Phonation Time and S:Z Ratio in Patients With Primary Muscle Tension Dysphonia

Objective: This study aimed to evaluate the influence of voice therapy on maximum phonation time (MPT) and S:Z ratio in patients diagnosed with primary muscle tension dysphonia (pMTD). The goal was to investigate whether pMTD is associated with reduced S:Z ratio and prolonged MPT.

Study design: Prospective cohort study.

Methods: A comparative analysis was conducted on a cohort of patients diagnosed with pMTD. Prevoice and postvoice therapy assessments of MPT and S:Z ratio were performed. Data from these measurements were analyzed to determine the impact of voice therapy on the studied parameters. A paired t test was used to evaluate MPT and S:Z ratio pretherapy and post therapy.

Results: Fifty-two patients met the inclusion criteria for the study, having completed a laryngology evaluation with diagnosis of pMTD and agreeing to voice therapy between July 22, 2021, and April 4, 2023. Sixteen of these patients completed a full course of voice therapy. The Voice Handicap Index-10 (VHI-10), MPT, and S:Z ratio were measured during initial evaluation as part of a complete laryngeal function study. A statistically significant reduction in VHI-10 scores was observed, with values decreasing from 17.81 (±2.81) pretherapy to 8.81 (±1.8) post therapy (P < 0.001). However, no significant differences were detected in MPT or the S:Z ratio following the intervention.

Conclusions: There is a lack of correlation between subjective evaluations of voice (VHI-10) and objective assessments (MPT and S:Z ratio), indicating that these objective parameters may not accurately reflect changes in voice quality following therapy in the pMTD population.

Lay summary: MPT and S:Z ratio do not appear to be uniformly impacted in patients with pMTD. Moreover, these measures do not consistently improve following voice therapy for pMTD.