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Morice and Kastelik1 have produced an excellent review of the management of chronic cough in adults. As stated by the authors, cough may arise from anywhere in the distribution of the vagus. One of the less common causes of chronic cough is disease of the ear2,3 due to stimulation of Arnold’s nerve.4 This nerve is an auricular branch of the vagus nerve which supplies the posterior and inferior parts of the auditory canal. In the absence of auricular symptoms an otoscope is not usually used in the investigation of patients with chronic cough. This diagnostic possibility may therefore be overlooked, resulting in many unnecessary examinations of the upper and lower respiratory tracts.5
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Authors’ reply
We thank the authors for their comments on our review of chronic cough in adults.1 The otoscopic examination of the external auditory meatus forms an important part of the assessment of patients with apparently idiopathic chronic cough. In 1832 Arnold described the ear-cough reflex, consisting of cough produced by a direct stimulation of the deep portion of the posterior wall of the external auditory meatus. In healthy subjects without chronic cough the reflex is present in 2–6% of the population.2–4 In chronic cough we hypothesised that vagal hypersensitivity might give rise to increased cough reflex sensitivity. However, infusion of capsaicin or citric acid into the external auditory meatus leads to cough only infrequently in our patients.
Cough arising from the ear is rare with only 15 cases having been reported.5 In some cases surgical treatment may be required. However, foreign bodies and ear wax have been the most commonly reported causes. The diagnostic clue is that other auricular symptoms are frequently reported. However, in apparently idiopathic cough otoscopy should be routinely performed.