Sensory Mechanisms in Primary Muscle Tension Dysphonia

PROJECT SUMMARY/ABSTRACT An estimated 2-8 million people in the United States struggle with primary muscle tension dysphonia (pMTD)— a functional voice disorder that adversely impacts daily living, occupational productivity, and quality of life and results in $2 billion in lost annual productivity costs due to absenteeism. Although pMTD leads to the same emotional, social, financial, and occupational hardships as organic, structural, and neurological voice disorders, its pathophysiology is poorly understood. These gaps make it difficult to understand what causes symptom com- plaints of vocal fatigue, vocal tract discomfort, odynophonia, and difficulties projecting or speaking for prolonged periods in patients pMTD—especially in the context of a lack of overt structural or neurological laryngeal abnor- malities. Although muscle tension and hyperfunction in the laryngeal system is the most proposed mechanism underlying symptoms, it is largely theoretical and based on anecdotal observations. Recent studies from the PI’s lab using well-vetted and validated physiological metrics to quantify tension and hyperfunction in the (para)laryngeal muscles found no group differences between patients with pMTD and healthy controls. However, patients with pMTD consistently reported significantly higher vocal effort, vocal fa- tigue, and vocal tract discomfort with voice use across these studies and self-reported significantly different sensory experiences on measures of interoceptive awareness. These findings suggest altered sensations with voice use in patients with pMTD may be an alternative mechanism underlying symptomology to simply muscle tension or hyperfunctional motor output. We test the central hypothesis that the somatosensory system plays a role in pMTD signs and symptoms across two aims. In Aim 1, we compare laryngeal sensation to pMTD symptom severity in patients with pMTD and controls using laryngeal aesthesiometer sensory testing. In Aim 2, we compare paralaryngeal and widespread musculoskeletal sensation to pMTD symptom severity in patients with pMTD and controls using mechanical pressure and dynamic temporal summation quantitative sensory testing (QST) assays. Outcomes of this proposal will elucidate the role of localized and central sensory mechanisms in pMTD and will lead to improved diagnostics and management for this debilitating voice disorder.