Arnold Nerve Reflex: Vagal Hypersensitivity in Chronic Cough with Various Causes

Abstract Background A higher incidence of Arnold Nerve Reflex (ANR) has been observed in patients with chronic cough. However, the different ANR response in various causes of chronic cough remains unclear. Furthermore, it is unknown whether ANR will change after effective treatment. Methods Patients with chronic cough were enrolled in the Guangzhou Institute of Respiratory Health. The causes of chronic cough were diagnosed via a validated management algorithm. Patients underwent an assessment of ANR response before and after one-month etiological treatment. Result A total of 127 patients with chronic cough and 55 healthy controls were enrolled. The positive response, defined as cough-only ANR or urge-to-cough (UTC), was present in 14.8% of cough variant asthma (CVA), 11.1% of upper airway cough syndrome (UACS), 15.4% of gastroesophageal reflex related cough (GERC), 4.8% of eosinophilic bronchitis (EB), 26.9% of unexplained cough (UC), respectively. No ANR or UTC was found in the healthy controls. The incidence of the positive response was higher in subjects with CVA, GERC and UC compared with healthy controls (all P 0.05). After one-month treatment, 87.5% of patients identified with a positive response changed to a negative response. In a subgroup analysis, an increased cough sensitivity to capsaicin was found in the patients with a positive response compared with the patients with a negative response (P Conclusion A positive ANR appears to be a sign of vagal hypersensitivity and can be reversed after effective treatment of chronic cough. However, while various causes of chronic cough share a similar feature of an elevated ANR response in a minority of patients, there appears to be limited usefulness in assessing the ANR because it does not appear to be a valid predictor of etiology of chronic cough or outcome of treatment.