Laryngeal and Global Somatosensation in Primary Muscle Tension Dysphonia

Primary muscle tension dysphonia (pMTD) is a functional voice disorder that reduces communicative abilities and adversely impacts occupational productivity and quality of life. Patients with pMTD report increased vocal effort, fatigue, discomfort, and odynophonia. Although laryngeal and paralaryngeal muscle tension and hyperfunction are the most commonly proposed mechanisms underlying these symptoms, recent studies suggest pMTD may have more to do with the somatosensory system. However, relationships between voice symptoms and somatosensory mechanisms are poorly understood, creating challenges for mechanistic-based pMTD management. The first objective was to compare laryngeal, paralaryngeal, and global somatosensation between subjects with and without pMTD. The second was to determine relationships between pMTD symptoms and somatosensation.

Fifty-two (20 pMTD and 32 control) subjects underwent laryngeal sensory testing with aesthesiometers, as well as peripheral mechanosensory and dynamic temporal summation testing to paralaryngeal and limb regions. Voice symptom severities (vocal effort, fatigue, discomfort, and odynophonia) were collected on 100-mm visual analog scales before and after laryngeal sensory testing. Participants also completed the Central Sensitization Inventory.

Patients with pMTD reported significantly higher laryngeal sensations (P = 0.0072) and voice symptom severities (P < 0.001) compared with the control group, and had significantly more vocal tract discomfort postlaryngeal sensory testing compared with the prelaryngeal sensory testing timepoint (P = 0.0023). However, there were no significant group differences in laryngeal airway protection responses suggestive of peripheral laryngeal hypersensitivities (P = 0.444). There were also no significant group differences on paralaryngeal or global sensitivities (P > 0.05), and no correlations between severity of voice symptoms and perceptual laryngeal sensations or hypersensitivities (P > 0.05).

Patients with pMTD perceive more sensitivities in the larynx and feel more sensations related to the voice (vocal effort, fatigue, discomfort, and pain). However, in general, patients with pMTD do not have abnormal peripheral laryngeal hypersensitivities, increased global somatosensation, or heightened central sensitivity. The lack of significant correlations between peripheral laryngeal hypersensitivities and voice symptom severity ratings suggests these outcome variables target distinct mechanistic constructs.