Effects of Laryngeal Manual Therapy on Primary Muscle Tension Dysphonia (MTD-1): Implications for MTD-1 Type.

The study investigated effects of laryngeal manual therapy on different types of primary muscle tension dysphonia (MTD-1). Interventional pre-test post-test design. Thirty-two traditional Iranian singers (mean age of 36.75 ± 9.34 years.) diagnosed with MTD-1, 8 female and 24 male, and recruited by convenience sampling completed the study. MTD-1 was classified as Morrison and Rammage's types 1-5, based on standardized criteria (1993). Pre-post-treatment measures were based on visual ratings of the larynx, acoustic analyses, auditory-perceptual assessments of voice (Auditory-Perceptual Rating Instrument for Operatic Singing Voice: EAI Scale Form), and the Persian Singing Voice Handicap Index (P-SVHI), reported before and after 10 sessions of laryngeal manual therapy (LMT). The most notable finding was that the number of cases with MTD-1 types 1 and 2 actually increased after treatment, while the number of cases with MTD-1 types 3, 4 and 5 decreased. The data suggested that MTD-1 types 3, 4, and 5 tended to convert to types 1 and 2 with LMT. Acoustic analyses showed a significant decrease in F0 (males only; P = 0.011), a sharp decrease in HNR from 23.26 dB to 14.74 dB (P = 0.000), and an increase in shimmer from 4.18% to 6.90 % while no appreciable change was found in jitter (P = 0.57). Mean P-SVHI score decreased significantly from 52.03 to 41.16 (P = 0.002) and EAI score increased from 4.41 to 6.31 (P = 0.000) after treatment. The primary finding was that the distribution of MTD-1 type changed after treatment in many cases, converting from one to another type. Acoustic as well as glottal closure measures for several participants revealed closure insufficiency after treatment, unveiled as hyperfunction was unloaded with LMT. For those participants, complementary treatments aimed at reinforcement of laryngeal closure functions would be appropriate.

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Conflict of Interest The authors declare no conflict of interest associated with the present work.