2018 Section 6 - Laryngology, Voice Disorders, and Bronchoesophalogy

Laryngeal sensory dysfunction

Breathing Score

14.0 16.0 12.0 10.0

8.0 6.0 4.0 2.0 0.0

Upper Airway Score

Cough Score

Figure 1 Symptom scores based on symptom frequency and severity scale in the CRC, PVFM, globus and MTD groups. All domains were higher in case groups vs controls ( P < 0.05). , cough; , PVFM; , globus; , MTD; , controls. CRC, chronic refractory cough; MTD, muscle tension dysphonia; PVFM, paradoxical vocal fold movement.

Voice Score

control group than the case groups. There was also a significant fall in FIF50 following the Voice Stress Test in 53% of participants in the case groups compared with 29% of healthy controls ( P = 0.008). Auditory perceptual voice quality ratings were made before and after cough reflex sensitivity testing. The degree of deterioration was significantly worse in the case groups than controls ( P < 0.001;Table 5). DISCUSSION We have identified that the discrete laryngeal dys- function syndromes of CRC, PVFM, globus and MTD each has abnormal laryngeal sensation and demon- strate overlap in sensory dysfunction during quanti- tative testing. These findings may suggest a common mechanistic pathway active in these syndromes and might implicate sensory neural dysfunction. Many of the concepts and clinical features that occur in chronic neuropathic pain could be usefully applied to the laryngeal dysfunction syndromes. For example, the concept of hyperalgesia, an increased sensitivity to pain can be reinterpreted in the case groups in this study. We found that patients had increased sensitivity to triggers for cough, dyspnoea, globus and dysphonia. The laryngeal paraesthesia questionnaire also identified symptoms that are trig- gered by innocuous stimuli, such as cold air, talking and perfume, analogous to the concept of allodynia in chronic pain. It also identified abnormal laryngeal sensation (paraesthesia) in the case groups. These findings may also suggest a role for central sensitiza- tion of the afferent reflex although peripheral sensiti- zation is present in chronic cough. 26 We found similar sensory abnormalities across the groups, supporting a common neuropathic origin for these functional syndromes. The mechanisms of the sensory dysfunc- tion require further study. A possible mechanism for allodynia is damage to sensory nerves, leading to

dose was significantly lower (increased sensitivity) in the cough ( P < 0.001) and PVFM ( P < 0.001) groups than healthy controls supporting hypothesis 1. There were no significant differences between the case groups with the exception of the PVFM group which was lower than the globus group ( P = 0.001). Objec- tive cough counting identified that cough frequencies per hour were significantly different between case groups and controls ( P = 0.002). There were higher cough counts in the PVFM ( P < 0.001) and MTD ( P = 0.005) groups than the healthy control group and a trend for higher cough counts in the CRC group ( P = 0.017). There was no significant difference in coughs per hour between the case groups, supporting hypothesis 2. Breathing: hypertonic saline challenge An abnormal fall in FIF50 was present in 57% of par- ticipants in the CRC group, 80% in the PVFM group, 25% in the globus group, 40% in the MTD group and 23% of healthy controls. The proportion of partici- pants with an abnormal fall in FIF50 was significantly different between case groups and controls ( P = 0.006) but was not significantly different between the clinical groups ( P = 0.087). There was no signifi- cant difference in dose-response slope between par- ticipant groups and controls ( P = 0.054; Fig. 2). Cross-stimulus responses Cross-stimulus responses were evaluated to provide stronger evidence for central sensitization and a common sensory pathway abnormality (Table 5). This refers to a primary stimulus, for example, vocal stress, eliciting sensory changes in another domain, such as cough. Voice Stress Testing of the case groups resulted in a significant increase in urge to cough ( P = 0.015), dyspnoea ( P = 0.001), laryngeal paraes- thesia ( P < 0.001) and dysphonia ( P < 0.001) when compared to controls. There was less variation in the © 2013 The Authors Respirology © 2013 Asian Pacific Society of Respirology

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