Spontaneous pneumomediastinum

A 18-year-old male patient with a medical history of ADHD, anorexia, bradycardia, and MRI-confirmed cerebral ischaemic stroke caused by vasoconstrictor syndrome, presented with sudden right-sided chest pain and dyspnoea. No trauma in history. Physical examination revealed blue and red petechiae on truncus and legs. Inconspicuous vital signs.

Chest X-ray showed air in the mediastinum, as well as free air in the supra-clavicular soft tissues. The findings were consistent with respectively pneumomediastinum and subcutaneous emphysema. CT of the neck, thorax and upper-abdomen showed mediastinal emphysema, as well as emphysema in the abdominal retroperitoneum, and in the subcutaneous thoracic - and supra-clavicular tissue. Air in the spinal canal was also detected. The cause was suggested to be rupture of the oesophagus, and an X-ray of the oesophagus with contrast was performed. A leakage could not be detected.

Pneumomediastinum is the presence of air within the mediastinum. It can be divided into spontaneous pneumomediastinum that is not preceded by trauma, surgery, or known pathology, or secondary pneumomediastinum, that is caused by specific pathology. It often presents with sudden onset of symptoms, most commonly chest pain, followed by dyspnoea, cough, neck pain and dysphagia [1-3]. Subcutanoeus emphysema is revealed in over half the patients [3]. Asthma, and asthma exacerbations has been found to be one of the most prominent risk factors for spontaneous pneumomediastinum [4]. In children, spontaneous pneumomediastinum can both be a consequence of an asthma exacerbation and a sign of a first asthma attack [4]. Pre-disposing risk factors such as a history of smoking, recent history of upper respiratory infection or strenuous physical activity has also been reported [3]. The pathophysiologic mechanism is suggested by Macklin et al (1944) to be alveolar rupture caused by increased intrathoracic pressure, with passage of air into the interstitium followed by migration of air toward the mediastinum, and further on towards the subcutaneous tissue of thorax, neck and abdomen, resulting in subcutaneous emphysema [5]. Pneumorrhachis, which is air in the spinal canal, can often be detected as well, and is caused by migration of air from the posterior mediastinum to the epidural space via the posterior surface due to lower resistance and lack of fascia [6]. A plain chest X-ray is a sensitive tool in diagnosing pneumomediastinum [1, 3]. Radiological signs to look for are the “ring sign”, which is air surrounding the pulmonary artery or either of its main branches, or the “thymic sail sign”, a sign more common in paediatric patients, resulting from an elevated thymus due to mediastinal air [3]. Often, a CT is performed, adding additional value when there are only small amounts of air in the mediastinum, and when differentiating spontaneous and secondary pneumomediastinum by trying to detect a potential underlying cause of the disease [1, 2]. Additional testing with bronchoscopy, oesophagoscopy or oesophagography can act as supplement when trying to detect an underlying cause, but is generally found to have limited value [1, 2]. However, it is recommended in highly suspicious cases of aerodigestive organ injury, such as Boerhaave`s syndrome or tracheobronchial tree rupture [2]. In most cases, spontaneous pneumomediastinum has a relatively benign clinical course, and responds well to conservative treatment with analgesia and rest [1, 2]. Written informed patient consent for publication has been obtained.