Pneumomediastinum

  • Etiology: barotrauma causing rupture of alveoli into interstitium, blunt thoracic trauma causing bronchus rupture, esophageal tear
  • Imaging: continuous diaphragm sign, spinnaker sail sign of mediastinal air between thymus + heart, can dissect into neck / peritoneum / retroperitoneum, tracheobronchial injury can also have pneumothorax

Cases of Pneumomediastinum

CXR and CT of pneumomediastinum
CXR AP shows air outlining the thymus (thymic sail sign) and that the diaphragm can be traced throughout its course (continuous diagphragm sign). Axial CT with contrast of the chest shows air in the posterior mediastinum in front of the spine.
CXR of tracheobronchial injury of left mainstem bronchus
CXR AP shows air in the superior mediastinum and neck, airspace disease in the left upper lobe, and a small amount of air in the left pleural space.