Teaching Case

Acute onset of cough and sorethroat

The patient presented to the emergency room with a 3 day history of cough and sore throat. There was no other significant past medical history like asthma. Clinical examination only showed occasional rales at lung bases. A chest radiograph was performed and revealed a pneumomediastinum. This was seen as a subtle radiolucent shadow of air outlining the lateral aspect of the aortic arch. There was no evidence of pneumothorax or pneumopericardium. A chest radiograph repeated 3 days later revealed complete resolution of the pneumomediastinum. No further investigations were required.

Pneumomediastinum is due to air in the mediastinal space especially in the antero-superior mediastinum. This may be spontaneous or secondary to a primary event. Spontaneous pneumomediastinum as in this case is the result of a sudden increase in intra-alveolar pressure resulting from acute bout of cough or vomiting. When the alveolar rupture occurs, the air dissects along lung interstitium and reaches the mediastinum along perivascular spaces. If the air extends towards the visceral pleura, a pneumothorax is a likely event. Pneumomediastinum is commonly seen in infancy and followed by in asthmatic children of older age. Spontaneous pneumomediastinum must be differentiated from pneumomediastinum secondary to sinister causes. The causes of pneumomediastinum are asthma, inhaled foreign body, post-operative ventilation, perforation of oesophagus, rupture of trachea or bronchus, trauma, post-resuscitation, pneumoperitoneum and measles. Abuse of crack cocaine results in pneumomediastinum due to violent cough.
A less than 2 years old child with no history of trauma and presenting with a pneumomediastinum should be investigated for an inhaled foreign body. If the etiology is unclear and associated with other symptoms like dysphagia or chest pain, a water soluble contrast study of the oesophagus should be considered.
Radiologic features in a frontal chest radiograph could be subtle. A lateral chest radiograph or a computed tomography would help identify the pneumomediastinum. The air in the mediastinum could lift the thymus away the heart giving it an ‘angel wings’ appearance. A medial pneumothorax could be confused with a localised pneumomediastinum. The continuous diaphragm sign is the result of air between the heart and diaphragm. A pneumopericardium would not outline the thymus or aortic arch.