Effects of intensive laryngeal manual therapy on acoustic measures of patients with muscle tension dysphonia: a single-subject study

Abstract Purpose This study aimed to investigate the effects of intensive laryngeal manual therapy on voice quality in patients with muscle tension dysphonia (MTD) using acoustic analysis. Methods Four female participants (21–25 years) with primary MTD were recruited via convenience sampling. Diagnosis was based on patient complaints, the Vocal Tract Discomfort (VTD) scale, videostroboscopy, and laryngeal palpation, ensuring no structural laryngeal pathologies or other medical conditions. This experimental A-B-A study design included three phases: baseline (six days, no intervention), intervention tracking (12 daily therapy sessions over two weeks), and maintenance phase (three sessions without intervention). Speech samples—sustained vowel phonation, counting—were recorded in an acoustic room using a Zoom H6 recorder. Acoustic parameters including Fundamental Frequency (F0), Jitter, Shimmer, Cepstral peak prominence (CPP), and Harmonic-to-Noise Ratio (HNR) were analyzed using Praat software. The 12-day intervention followed the Laryngeal Manual Therapy (LMT) protocol, administered by a single therapist. Treatment included circular and kneading massages targeting the sternocleidomastoid muscles, supralaryngeal area, hyoid bone, and larynx. Results Visual analysis revealed varied individual responses among participants. HNR values exhibited diverse trends during the intervention phase, with some participants showing considerable improvement. MPT, and CPP values fluctuated across participants, with notable increases observed in some cases. F0 values remained stable for some participants, while others showed variations. Shimmer and Jitter values also varied among participants, with some demonstrating improvements post-therapy. Conclusions This study provides insights into the potential benefits of intensive LMT for managing MTD. Both visual and quantitative analyses highlight the varied individual responses to therapy, underscoring the importance of personalized treatment approaches in MTD management. These findings contribute to the understanding of the therapeutic potential of LMT and its implications for voice quality improvement in MTD patients, offering guidance for future research and clinical practice in this field.