Cough is one of the most common symptoms in medicine. It is the fifth most common reason for visits to physicians. More than 40 million visits to primary care physicians per year are for evaluation of cough. Studies in which patients have been asked whether they perceive a cough as abnormal have found that many people do not. Healthy people do not need to cough and do not cough. The cause of cough ranges from very serious abnormalities to psychogenic factors. The range of the differential diagnosis is extensive; however, certain conditions occur more frequently, and these are the emphasis of this article.

Cough has two main functions: (1) to help protect against aspiration and (2) to help propel secretions out of the chest. The physiologic basis of cough is as follows. Cough receptors are located in various areas, including the external auditory canal, paranasal sinuses, pharynx, nares, larynx, tracheobronchial tree, pericardium, pleura, diaphragm, and stomach (Table 1). The sequence of the neuronal pathways is from the afferent nerves to the cough center, located in the brain, to the efferent nerves, and finally to the effector organs and the cough.

Most coughs are due to stimulation of the cough receptors. Mechanisms of stimulation are foreign body aspiration, irritant gases, infections of the bronchi, granulomas in the tracheobronchial tree, and neoplasms. Smoking is by far the most important of the environmental agents causing chronic cough. The mechanism of the cough is from irritation of the cough fibers located in the larynx, trachea, and bronchi.

Coughing may produce considerable distress, including (1) cardiothoracic symptoms—sore chest muscles and chest pain, fractured ribs, and pneumothorax or pneumomediastinum; and (2) noncardiothoracic symptoms—sleep disturbance, anorexia and vomiting, headache and syncope, urinary incontinence, subconjunctival hemorrhage, social self-consciousness, and disruption of surgical wounds.

Coughing can be either acute or chronic, and a cough of 4 or more weeks in duration is considered chronic. The most common cause of an acute, transient cough is the common cold. The most common causes of chronic cough include asthma, postnasal drip, sinusitis, and chronic bronchitis.

Often, the cause of cough can be determined from a comprehensive history and physical examination. In fact, some studies estimate that the cause of cough is found in up to 80% of cases on the basis of the history and physical examination.<sup>14 Parks D.P., Ahrens R.C., Humphries C.T. , et al. Chronic cough in childhood: Approach to diagnosis and treatment J Pediatr 1989 ;  115 : 856  [cross-ref]

Cliquez ici pour aller à la section Références</sup> Thus, evaluation of a patient with cough is one of the clinical situations in which one's clinical skills can be used to a great advantage.

The first step in successful management of chronic cough is to establish the correct diagnosis. A typical work-up includes (1) a thorough history, including questions about the nature of the cough, (2) a complete physical examination, and (3) when necessary, appropriate laboratory studies to evaluate the nose, sinuses, chest, and esophagus.