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Nose and paranasal sinuses
including computed tomography imaging of sinuses for anatomic abnormalities or possible silent sinus disease and further treatment of sinusitis if diagnosed [5,10]. NEW HORIZONS IN DIAGNOSIS AND THERAPY As noted, UACS is primarily a clinical diagnosis that lacks sensitive or specific diagnostic testing. How ever, methods are being studied that may prove helpful in the future to distinguish various cough syndromes. Maniscalco et al. [25 & ] describe a method of distinguishing between PND and GERD versus CVA and nonasthmatic eosinophilic bronchitis using exhaled nitric oxide. They found that exhaled nitric oxide was increased in patients with CVA and nonasthmatic eosinophilic bronchitis when com pared to GERD and PND. Given that GERD has its own objective symptoms and diagnostic testing available, exhaled nitric oxide may help distinguish PND from the other chronic cough diagnosis. As mentioned previously, capsaicin inhalational testing has been used to assess for patients with cough hypersensitivity. However, capsaicin testing itself remains a nonspecific diagnostic examination as there is a wide variation in sensitivity to capsaicin in the general population [14]. However, studies are looking into use of capsaicin inhalation testing as a means to help diagnose sensory hyperactivity [26 & ]. Current treatment recommendations of UACS continue to be based on assumption that it is a sinonasal disease process. Other therapies being examined include use of montelukast as well as capsaicin desensitization. A study looked at treat ment with montelukast for 2 weeks and showed improvement in patient-reported cough symptoms. The study also showed increased cough thresholds on capsaicin inhalation testing [27 & ]. Given that there is an association with capsaicin sensitivity and cough, use of capsaicin tablets to desensitize cough receptors has also shown promising results in improving cough symptoms [28 & ,29 & ]. CONCLUSION PND, now known as UACS, remains an imprecise diagnosis and its mechanism, as first described by Dobell 150 years ago, is debated to this day. Cur rently, management of UACS still assumes a sino nasal source for chronic cough and therapies revolve around management of rhinitis or sinusitis. More recent research has shown that unexplained chronic cough symptoms may be related to sensory hyper sensitivity of airway cough receptors and alternative therapies are being studied to treat cough symptoms
such as through desensitization of capsaicin sensi tive cough receptors. Work still needs to be done to better understand the mechanism of unexplained chronic cough, but we may find that PND will become an outdated term for a disease process that is no longer applicable.
Acknowledgements None.
Financial support and sponsorship None.
Conflicts of interest There are no conflicts of interest.
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Volume 24 Number 1 February 2016
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