Post-nasal drip syndrome—a symptom to be sniffed at?

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Abstract

The syndrome or pseudo-syndrome of post-nasal drip (PNDS) represents a diagnostic label which is unhelpful in the understanding of chronic cough. There is no accepted definition of PNDS and no accepted method of measurement. The symptom of mucus dripping down the back of the throat occurs in normal subjects and is also reported by many patients in ENT clinics who do not have a cough. The lack of any clear pathological or biochemical tests makes the syndrome both a catch-all and a dustbin.

Introduction

The literature is sharply divided in its use of the term PNDS. Most American authors use the term widely and find a very high incidence in patients reporting to the cough clinic. In Europe PNDS is much less frequently recognized. Could the differences between these societies reflect the different incidence of PNDS? PNDS is not mentioned in much of the standard literature; indeed, the Oxford Handbook of Clinical Specialities goes straight from post-menopausal to post-natal. It is becoming increasingly recognized that the localization of sensation within the thorax and upper airways is poor and that as our understanding of the causes of cough evolves symptoms such as airway hyperresponsiveness may have their origin in oesophageal disease. With the developments of impedance technology post-nasal symptoms may be found to be related to laryngopharyngeal reflux rather than any pure post-nasal problem.

The reported incidence of post-nasal drip syndrome (PNDS) varies widely within the chronic cough literature [1] (Table 1). It seems most unlikely that these large differences in incidence in PNDS are only due to different patient characteristics. It suggests a fundamental difference in the definition of PNDS or, indeed, whether PNDS actually exists as a separate entity.

Collins Dictionary of Medicine defines a syndrome as “a unique combination of sometimes apparently unrelated symptoms or signs forming a distinct clinical entity”. In contrast ‘a symptom is a subjective perception suggesting a bodily defect or malfunction’. Thus, whilst there is no denying that some patients with chronic cough complain of the sensation of ‘something running down the back of the throat’ for PNDS to qualify as a syndrome there should be associated other features, or physical signs. Ideally, the triad of chronic cough, post-nasal drip and observable retropharyngeal mucus should consistently occur together and be ‘the distinct effects of a common cause’.

Section snippets

Rhinosinusitis and chronic cough

A number of clinical syndromes are associated with rhinosinusitis and chronic cough [2]. However, a distinction should be made between those conditions where the rhinosinusitis is merely part of a generalized abnormality and isolated rhinosinusitis. In primary ciliary dyskinesia rhinosinusitis may be the presenting complaint [3] but is the disease in the nasopharynx the cause of the chronic cough? Patients almost invariably have a significant degree of bronchiectasis and the productive cough is

Pathophysiology

The associated features of PNDS such as throat clearing and hoarseness are frequently associated with other causes of cough, particularly reflux disease [5]. Symptoms are poorly localized within the upper airways. Laryngeal inflammation may be easily detected in patients with reflux disease. It would be unsurprising were patients with reflux not to have post-nasal inflammation.

A further problem with the description of PNDS as a cause of cough is in the pathological mechanisms leading to the

Epidemiology

The incidence of PNDS as a reported diagnosis for chronic cough varies enormously [8]. A pattern emerges, however, in that those clinics reporting the highest incidence of PNDS come from the United States, whereas it is much less frequently reported in the European experience. In a study by Proctor & Gamble (US980399, Dr David Hull, personal communication) patients were asked by telephone interview whether they suffered post-nasal drip during an episode of cough/cold in the preceding 6 months.

Treatment

One of the major points arguing for the treatment of PNDS as a syndrome causing chronic cough is the response to specific pharmacological therapy [9]. This assumption, however, is incorrect, since the drugs advocated for PNDS due to perennial rhinitis or post-viral upper respiratory tract infection are the older generation sedating antihistamines or antihistamine/decongestant combinations [7]. Such medications are anything but specific. The fact that these drugs are sufficiently lipophilic to

Conclusion

Post-nasal drip syndrome is a symptom masquerading as a syndrome. It varies widely across different societies and there is no objective test. The term rhinitis or rhinosinusitis should be used in preference.

References (21)

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