The search for the hypersensitivity in chronic cough

Identifying Practice Gaps Among Otolaryngology Providers for the Treatment of Chronic Cough

Objective

Increasing evidence over the last decade suggests that many cases of unexplained chronic cough (UCC) have a neurogenic etiology, with laryngeal hypersensitivity (LH) being identified as a key mechanism. Official guidelines since 2015 have adopted use of neuromodulators and adjuvant speech therapy as a result, but historically implementation of guidelines is slow. Our survey aimed to investigate gaps in diagnosis and management practices of otolaryngology providers in caring for patients with UCC.

Study Design

Cross-sectional study.

Setting

Survey.

Methods

12-item survey was distributed to 110 otolaryngology practitioners experienced in diagnosis and treatment of chronic cough at a regional otolaryngology continuing education conference. Statistical analysis included Kendall's Tau Rank Correlation to measure the ordinal association between responses to questions, and Fisher's exact test to determine if there were associations between responses and years of career experience.

Results

Forty eligible respondents underwent subsequent analysis. There was no association between frequency of identifying LH as a primary etiology and use of neuromodulators (τ = 0.23, P = .10). However, there was a significant correlation between LH and referrals to speech therapy (τ = 0.27, P = .05). Fisher's exact test did not reveal any significant differences among any responses based on practitioner experience.

Conclusion

Our results indicate a possible disparity in treatment of UCC with neuromodulators and the utilization of speech therapy despite guideline recommendations advocating for neuromodulators with adjuvant speech therapy. Further research with larger sample sizes and more specific inquiries is necessary to elucidate this association and control for any regional differences.

Is laryngeal hypersensitivity the basis of unexplained or refractory chronic cough?

Refractory chronic cough (RCC) and unexplained chronic cough (UCC) are common problems seen in primary care and subspecialty clinics. The role of cough hypersensitivity and laryngeal dysfunction in contributing to the persistence of cough in RCC/UCC is not well recognised. Data of patients with RCC and UCC evaluated in 2019 by an interdisciplinary cough clinic led by a pulmonologist and speech-language pathology team was reviewed. Patients completed validated questionnaires including the Leicester cough questionnaire (LCQ), voice handicap index (VHI) and dyspnoea index (DI) questionnaire at initial encounter. Presence of cough hypersensitivity was based upon a history of allotussia and hypertussia. Laryngeal dysfunction was diagnosed in those with a history of laryngeal paresthesias, throat clearing, voice abnormalities, upper airway dyspnoea and documentation of functional or anatomic laryngeal abnormalities on nasoendoscopy. Of the 60 UCC/RCC patients analysed, 75% of patients were female and 85% were over 40 years of age. Cough hypersensitivity was documented in all patients and multiple cough triggers occurred in 75% of patients. 95%, 50% and 25% of patients reported laryngeal paresthesias, voice abnormalities and upper airway dyspnoea, respectively. Significant associations between LCQ and VHI and DI scores occurred when adjusting for age, sex, ethnicity and body mass index. Laryngeal functional abnormalities were documented on 44 out of 60 patients on nasoendoscopy. Hypertussia, allotussia and laryngeal dysfunction are common in patients with RCC and UCC. Evaluation of UCC and RCC can delineate laryngeal hypersensitivity and allows appropriate treatment to be directed at this phenotype.

Short- and Long-term Effects of Neuromodulators for Unexplained Chronic Cough

Objective

To evaluate the short- and long-term effects of tricyclic antidepressants (TCAs) and gabapentin in the treatment of unexplained chronic cough (UCC).

Study Design

Prospective cohort.

Setting

Tertiary care hospital.

Subjects and Methods

Patients seen between July 2016 and March 2017 were included following a formal workup and clinical evaluation indicative of UCC. Patients were placed on either a TCA (amitriptyline or nortriptyline) or gabapentin. Leicester Cough Questionnaire (LCQ) and percentage improvement scores were obtained prior to treatment initiation and at 2 and 6 months of neuromodulator treatment. A linear mixed model assessed the change in LCQ score between the 2 treatment time points and baseline scores.

Results

Twenty-eight patients completed a total of 37 neuromodulator trials. Gabapentin demonstrated statistically significant improvement in LCQ scores at 2 months (2.48 points, P≤ .01) and 6 months (5.40 points, P = .01) of treatment as compared with baseline. Patients taking TCAs demonstrated statistically significant improvement of LCQ scores at 2 months of treatment (3.46 points, P≤ .01). However, the majority of patients discontinued treatment, most commonly secondary to the development of tachyphylaxis after 2 months, precluding analysis at 6 months.

Conclusion

While both neuromodulator classes demonstrated short-term benefit, the majority of patients discontinue treatment prior to 6 months, with patients taking TCAs discontinuing more frequently than patients on gabapentin. Future investigations are warranted evaluating tachyphylaxis and the utility of dual treatment therapies designed to address peripheral and central sensory pathways involved in UCC.