2018 Section 6 - Laryngology, Voice Disorders, and Bronchoesophalogy

AE Vertigan et al .

axonal degeneration, and then during the regenera- tion and healing process, axons from one sensory receptor connect to fibres that previously carried signals from a different sensory receptor. This damage usually starts in unmyelinated fibres of afferent nerves. 27 It would be useful to examine these features in CRC, PVFM, globus and MTD. In addition to the similarities between laryngeal dysfunction and chronic pain, the results are in con- cordance with the ‘Cough Hypersensitivity Syndrome’ described by Morice. 28 This syndrome proposes that chronic cough regardless of aetiology, is due to under- lying cough reflex hypersensitivity primarily due to a connection between symptoms and reflux. There are a number of similarities between the results of the current study and Cough Hypersensitivity Syndrome. Participants in the case groups also demonstrated different motor responses as demonstrated by the Timed Swallow Test and the voice assessment. The underlying mechanisms for these findings are unclear. It is possible that conditions which cause chronic inflammation such as CRC result in laryngeal damage that leads to common sensory abnormalities and variable motor response. Although some of the participants in this study had confounding diag- noses, they had been medically managed for these conditions. Our observations may also have significant treat- ment implications. Specifically, neuromodulators such as pregabalin is successful in neuropathic pain may also be effective in laryngeal dysfunction syn- dromes. Chronic cough has been shown to respond to pharmaceutical treatment for sensory neuropathy, such as gabapentin. 6,29 This approach has not been investigated in other laryngeal disorders. Our data suggest a need for randomized trials of neuromodu- lators in the laryngeal dysfunction syndromes. There were some confounding factors in this study which may have influenced the results. First, a small proportion of participants in most groups had a pre- vious history of using ACE inhibitors, although this was not significant between groups, and participants had ceased this medication for at least several weeks before testing. Participants did not undergo formal testing for gastroesophageal reflux; hence, it is possi- ble that some of the study findings were due to undi- agnosed gastroesophageal reflux. Finally, the actual cough frequency was high in the healthy controls however it was significantly less than the clinical groups. The clinical significance of these results requires further consideration. There were clinically signifi- cant results for C5 dose, coughs per hour and all voice testing results. However, the clinical signifi- cance of the dose-response slope is less clear. Cross -stimulus responses were clinically significant for CAPE-V ratings, and worst urge to cough, modified Borg scale and Borg laryngeal paraesthesia scales. However, the changes in urge to cough, Borg laryn- geal paraesthesia and modified Borg scale were less significant. In conclusion, these laryngeal conditions can be perplexing and challenging to manage in the clinical setting. This is the first study to systematically Swallowing Timed swallow test (mL/Sec) M (SD) 19.8 (6.8)* 18.2 (8.6)* 17.6 (12)* 19.7 (7.6) 29.9 (12.5) 0.002 0.802 Cough Reflex Sensitivity C5 dose (Mdn IQR) 6.92 (1.96–15.7)* 3.92 (1.96–7.84)* 15.7 (15.7–62.7)# 7.84 (3.92–19.63) 62.7 (9.8–203.8) < 0.001 0.008 Cough/hour 25.0 (28.8) 56.7 (18.0)* 14.2 (4.8) 24.9 (18.4)* 6.5 (7.3) 0.002 0.199 Breathing Dose response slope (Mdn, IQR) 1.5 (0.5–3.8)* 1.1 ( - 0.4–2.0) 0 1.9 (0.05–4.3) 0.9 (0.1–1.3) 0.054 0.101 % Abnormal fall 57% 80% 25% 40% 23% 0.006 0.087 Vocalization Voice Handicap Index 21.6 (20.5) + 31.1 (27.3)* 29.6 (20.7) 51 (22.3)* 4.6 (6.5) < 0.001 0.001 CAPE-V overall score 30 (18.8)* 30.4 (22)* 32.2 (24.1)* 56.1 (24.5)* 3.6 (6.6) < 0.001 < 0.001 Maximum phonation time (seconds) 11.1 (5.3)* 9.3 (4.8)* 10.2 (5.6)* 8.3 (3.8)* 19.7 (5) < 0.001 0.276 Dysphonia severity index 3.2 (2.1)* + 2.3 (2.4)* 2.6 (2.2)* 2.3 (1.6)* 6.5 (2.1) < 0.001 0.308 * P < 0.0125 vs controls; + P < .008 vs MTD; # P < 0.008 vs PVFM; † P -values of analysis of all groups; ‡ P -values of analysis of case groups.

hypothesis 2 ‡

P -value

hypothesis 1 †

P -value

controls n = 13

Healthy

MTD n = 18

Globus n = 11

PVFM n = 28

n = 33

CRC

Quantitative

Sensory Test

Table 4 Results of quantitative sensory testing Domain

CRC, chronic refractory cough; MTD, muscle tension dysphonia; PVFM, paradoxical vocal fold movement.

Respirology (2013) 18 , 948–956

© 2013 The Authors Respirology © 2013 Asian Pacific Society of Respirology

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