The effect of speech rehabilitation therapy for muscle tension dysphonia on global postural strategy

Purpose: To examine postural control in muscle tension dysphonia (MTD) before and after a specific speech rehabilitation program. Methods: Twenty-six patients diagnosed with MTD underwent posturographic analysis before and after speech rehabilitation. Romberg test was performed with eyes open (EO), eyes closed (EC) and during the head retroflex (ECR) and the occlusal (ECO) tests to investigate the role of cervical and stomatognathic proprioception. The analyzed posturographic parameters were the Sway area (S), length (L) of the center of pressure (CP) oscillations, coordinates of the CP on frontal and sagittal plane, stomatognathic interference index (SSI) and cervical interference index (CSI). Considered parameters of microphone perturbation were the Jitter (JITT), Shimmer (SHIM) and noise to harmonic ratio (NHR). Results: Sixteen patients (61.5%) exhibited values above those expected for at least one of the posturographic parameters during one or more of the conditions with eyes closed. There were values outside the normal range in the Sway area under EC and ECR conditions, and in the coordinates of the center of pressure on the sagittal plane posteriorly under EC conditions. Highly destabilizing SSI was recorded in six of the patients (23%), while CSI was recorded in 18 (69.2%). After rehabilitation, seven patients continued to show posturographic alterations. There was a statistically significant improvement of all previous altered posturographic parameters. Eight patients whose S parameters had returned to the normal range after speech therapy, also showed significant improvement of all microphone signal parameters. Conclusion: This study shows that MTD might interfere with global postural strategy through the involvement of all cervical muscles proprioception. The strong correlation between the improvement of vocal and postural control, suggests that a posturographic study may be useful in the planning of the speech therapy, as well as in the evaluation of its effectiveness in terms of muscle relaxation.