Does More Compression Mean More Pressure? A New Classification for Muscle Tension Dysphonia

Objective: The aims of this study were to test the hypothesis that greater supraglottic compression (anteroposterior or lateral) correlates with higher subglottic pressure (SGP) and to develop a classification of muscle tension dysphonia (MTD), based on the degree of supraglottic compression during speech. Method: A prospective, cross-sectional study was conducted in a series of 37 consecutive patients diagnosed with MTD with an altered aerodynamic profile characterized by high SGP (more than 90 mmH[subscript 2]O). Supraglottic anteroposterior and lateral compression were categorized in three grades and assessed during the laryngoscopic examination. All patients completed the Spanish Voice Handicap Index (VHI) questionnaire and completed an acoustic and aerodynamic voice assessment. The relationship between compression grade and VHI with SGP was analyzed. Results: More than 90% of patients demonstrated some degree of anteroposterior compression, and 67% had some degree of lateral compression. The mean (SD) SGP was 111.03 (16.7) mmH[subscript 2]O, and the mean VHI was 27.86 (12.5). The degree of SGP was statistically different in the different grades of anteroposterior compression, and also anteroposterior compression correlated with an SGP (p < 0.05). The degree of lateral compression was not correlated with SGP. Neither the degree of anteroposterior or lateral compression nor the value of SGP was found to correlate with VHI. Conclusions: Because grade of anteroposterior compression correlates with SGP, these grades can be used for diagnosis and follow-up of MTD patients. To this end and on this basis, we propose a new classification for MTD. Unlike the established classification, our proposed one makes it possible to combine different laryngoscopic features, improving the description of the larynx during phonation.