Toillustrate various radiological signs seen with pneumomediastinum and commonly associated abnormalitieson chest radiographs, and their correlating CT scan or contrast swallow. To enable to reader to recognise variousradiological features of pneumomediastinum. To provide a brief commentary on the role of various imaging modalities in the assessment of identified cases of pneumomediastinum.

Pneumomediastinum is defined as the presence of air in the mediastinum. This can be spontaneous or secondary, with iatrogenic, traumatic and non-traumatic causative factors.1,3There are various radiological signs associated with the pneumomediastinum, and it can present with concurrent abnormalities, such as pneumothorax, pneumoperitoneum and pneumopericardium.3-5Pneumomediastinum is rare and diagnosis is usually made through plain radiographs.1,4However, further imaging such as CT scans and contrast swallows can be used for differentiating diagnoses, assessing the extent of the pneumomediastinum and identifying the causative pathology.5-9Identifying the underlying pathology can...

Pneumomediastinum presents with a variety of radiographic features. It is mostly seen astranslucent gasoutlining mediastinal contours, including: subcutaneous emphysema pneumopericardium - gas anterior to pericardium double bronchial wall sign - gas outlining bronchial wall continuous diaphragm sign - gas trapped posterior to pericardium ring around artery sign - gas around pulomary arteries tubular artery sign - gas outlining major aortic branches extrapleural sign - gas between parietal pleura and diaphragm Naclerios V sign - left lower lateral mediastinal border, usually due to oesophageal rupture gas...

Pneumomediastinum is rare and can represent potentially dangerous pathology. Clinical signs can be non-specific and imaging is often required for diagnosis. This review aims to illustrate a collection of common and uncommon radiographic features of pneumomediastinum to better enable the reader in diagnosis. Whilst itcanusuallybe diagnosed on plain chest radiographs, most patients progressed to further imaging. This assisted with identifying the underlying cause, and therefore with determining themanagement plan.

Dr Tahnee Paterson has recently been accepted into theWestern Australia Radiology Training Program and will commence her registrar training in 2020. Dr Ashu Gupta is a radiologist at Fiona Stanley Hospital in Perth, Western Australia, and has a special interest in chest and cardiac radiology. Dr Charles Jenkinson is a cardiothoracic surgery advanced trainee, who trained in Western Australia.

Kouritas VK, Papagiannopoulos K, Lazaridis G, et al. Pneumomediastinum. J Thorac Dis. 2015; 7(1):s44-s49. Boo SL, Rafati F, Pucci M. Image: pneumomediastinum following sternutation after cocaine insufflation. Postgrad Med J [Serial on the Internet] 2019 [cited 2019 March 31]; 0(1) [about 1 screen]. Available fromhttps://doi:10.1136/postgradmedj-2019-136391 Elkholy K, Akhtar H, Landa E, Malyshev Y, Sahni S. A case of pneumomediastinum and pneumoperitoneum with concurrent massive subcutaneous emphysema due to repositioning of a tracheostomy tube. Cureus [serial on the Internet] 2019 [cited 2019 March 13]; 11(1) [about...