Laryngeal hypersensitivity may be a key factor in refractory and unexplained cough.
Summary Refractory chronic cough (CRC) 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 cough persistence in RCC/UCC is not well recognized. Data were reviewed from patients with CRC and CCU evaluated in 2019 by an interdisciplinary cough clinic led by a pulmonologist and a speech-language pathology team. Patients completed validated questionnaires including the Leicester Cough Questionnaire (LCQ), Voice Handicap Index (VHI), and Dyspnea Index (DI) questionnaire at the initial encounter. The presence of cough hypersensitivity was based on a history of allotusia and hypertusia . Laryngeal dysfunction was diagnosed in those with a history of laryngeal paresthesias, throat clearing, voice disturbances, upper airway dyspnea, and documentation of functional or anatomical laryngeal abnormalities on nasoendoscopy. Of the 60 UCC/RCC patients analyzed, 75% of the patients were women and 85% were over 40 years old. 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 alterations and upper respiratory tract dyspnea, 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 in 44 of 60 patients undergoing nasoendoscopy. Hypertusia, allotusia, and laryngeal dysfunction are common in patients with CRC and UCC. Evaluation of UCC and RCC can delineate laryngeal hypersensitivity and allows appropriate treatment to target this phenotype. * Allotusia : non-tussive stimulus that causes an exaggerated response. * Hypertusia : Responds more intensely to a stimulus than a healthy person. |
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Defining the characteristics and better understanding laryngeal hypersensitivity may help in the treatment of refractory and unexplained cough, according to a new study.
The researchers reviewed data from questionnaires completed by patients with refractory chronic cough (CRC) and unexplained chronic cough (UCC), which are common problems seen in primary care and subspecialty clinics.
The study, published in ERJ Open Research , found that cough hypersensitivity was documented in all 60 patients analyzed, with multiple cough triggers in 75%. The study also found that 95% complained of laryngeal sensations that triggered cough, 50% reported voice abnormalities, and 25% reported difficulty breathing in the upper airways.
Nasoendoscopy examination documented laryngeal functional abnormalities in 44 of 60 patients, all of whom were examined within the University of Utah Health System. Data was collected in 2019.
In most patients, cough is thought to be caused by gastroesophageal reflux disease (GERD), rhinosinusitis, or cough variant asthma. However, these causes do not explain many cases. Estimates place cases of UCC and RCC between 5% and 42% of patients with chronic cough.
Cough hypersensitivity, characterized by decreased cough thresholds and non-noxious stimuli, has been proposed as an explanation for refractory and unexplained cough.
In the study, almost all patients (57 of 60) described a tickle, lump or sensation in the throat, irritation, dry throat, and presence of mucus in the throat. Women reported a higher prevalence of abnormal throat sensations, which were associated with increasing age. Nearly half of the patients reported frequent throat clearing.
More than half of the patients reported voice abnormalities , including hoarseness, loss of voice when speaking or singing, changes in pitch, or hoarse voice. A quarter reported symptoms of upper respiratory dyspnea, such as throat constriction and difficulty breathing.
Structural abnormalities were found in almost half of the patients, and most presented with redness or irritation, as well as edema. Only 5 patients had normal appearance and laryngeal function. Of the 60 patients, 24 had overlapping structural and functional abnormalities.
Treatment included behavioral speech therapy (BST; 56 of 60 patients), and 34 completed the treatment course. Management of comorbid obstructive sleep apnea (OSA) was also recommended, with 43% of patients completing treatment and 22 new OSA diagnoses given. Treatment for patients with OSA included behavioral speech therapy, continuous positive airway pressure therapy, and management of other conditions such as GERD.
Cough hypersensitivity in CRC and CCU is attributed to changes in cough pathways within the central and peripheral branches of the cough reflex pathways. Peripheral sensitization and alteration of the modulatory influences of the central descending pathways are thought to be related to cough, the authors said. However, much remains to be understood about the mechanistic causes in terms of neurostructure and neurofunctionality.
However, they added, "there is increasing clinical recognition of the role of the larynx and surrounding structures in chronic cough."
The efficacy of BST points to a role for laryngeal hypersensitivity in the diagnosis of chronic cough, the authors said. Many of these patients are treated for GERD or OSA without success in reducing cough.
Nearly 75% of patients in the study were women, and 85% of all patients were over 40 years old. Patients over 70 made up one-third of the patients and had the longest cough duration.
Conclusion This report highlights the prevalence of a constellation of symptoms that typify laryngeal dysfunction and cough hypersensitivity with a call to designate laryngeal hypersensitivity as a specific cough phenotype.
Although more work is required to validate the proposed criteria for laryngeal hypersensitivity, its high prevalence and response to BST makes it necessary to evaluate laryngeal hypersensitivity during the treatment of the patient with chronic cough. The use of specific questions to identify both laryngeal dysfunction and cough hypersensitivity may delineate laryngeal hypersensitivity syndrome and facilitate the development of therapies targeting the underlying neuropathic basis of cough. |
Reference
Sundar KM, Stark AC, Hu N, et al. Is laryngeal hypersensitivity the basis of unexplained or refractory chronic cough? ERJ Open Res. 2021; 7 (1): 00793-2020. doi:10.1183/23120541.00793-2020
