The radiographic presentation of air within the mediastinal planes is usually an indication of serious breach of an intrathoracic luminal structure. The unprovoked appearance of pneumomediastinum demands exclusion of such serious pathology before a course of conservative management can be safely pursued. A case of spontaneous pneumomediastinum in a patient with a history of asthma in childhood is presented.

CASE REPORT

A 22 year old man presented to the accident and emergency department with progressive dyspnea and neck pain and a two day history of non-productive cough and malaise, associated with cold sweats but no vomiting. He also had increasing dull chest pain, exacerbated by coughing, talking, breathing, and swallowing. He had multiple previous stays in hospital for childhood asthma but was not taking current medication and denied recreational drug use. He was apyrexial and examination revealed a resting tachycardia with distant heart sounds but a normal blood pressure. There was no evidence of Hamman’s crunch. Respiratory excursions and air entry were globally decreased but additional breath sounds were absent. No clinical signs of chest infection were found.

Haematology and biochemistry tests were normal but chest radiography revealed a pneumomediastinum with no associated pneumothorax. Gastrografin swallow and computed chest tomography (fig 1) showed extensive pneumomediastinum but no evidence of contrast leak or pleural effusion. The patient was treated conservatively with intravenous fluids and antibiotics and denied oral intake. He subsequently developed cervical surgical emphysema but vital signs remained stable and he tolerated a light diet the following day. He was discharged after three days. At one week’s outpatient follow up, the patient was well, with no further chest pain or dyspnea. His chest was clinically clear and chest radiography was normal.

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Figure 1

 Computed tomography showing spontaneous pneumomediastinum.

COMMENT

Spontaneous pneumomediastinum is reportedly rare but may be an under-diagnosed condition. Chest pain and dyspnoea are the usual presentations.¹ Subcutaneous cervico-facial emphysema and Hamman’s auscultatory sign, named after the author who first described the condition, are common findings.

Manual straining, coughing bouts,^1,2 sneezing,³ and inhalational drug use⁴ are preludes to spontaneous pneumomediastinum development. The mechanism in common is sudden increased intrathoracic pressure induced by an effected Valsalva manoeuvre.⁵ Consequent rupture of marginal pulmonary alveoli, allowing bubbles of air to dissect along the vascular sheaths and connective tissue planes to the mediastinum has been showned by perfluorocarbon radiographic imaging.⁶ Although our patient did not have acute bronchospasm, his history of severe childhood asthma suggests airway hyper-reactivity, previously described to be associated with spontaneous pneumomediastinum.⁷ Peripheral alveolar air trapping and air pressure surges with coughing are suspected to have lead to alveolar rupture.

On its own, spontaneous pneumomediastinum is usually a benign, self limiting condition and the treatment is conservative.² Rarely, life threatening tension pneumopericardium may occur. Importantly, conditions carrying high mortality and morbidity such as bronchial or oesophageal rupture must be excluded by endoscopy and contrast radiography. Associated tension pneumothorax must also be excluded. Recurrence is uncommon.²

In conclusion, spontaneous pneumomediastinum should be suspected in young patients with a history of asthma presenting with chest pain. It is largely a benign condition best treated expectantly, but serious pathology such as bronchial or oesophageal rupture or associated tension pneumothorax or pneumopericardium must be excluded.