Pneumomediastinum

Pneumomediastinum is the presence of extraluminal gas within the mediastinum. Gas may originate from the lungs, trachea, central bronchi, oesophagus, peritoneal cavity and track from the mediastinum to the neck or abdomen.

In the setting of trauma, if pneumomediastinum is visible on chest x-ray it is termed overt pneumomediastinum whereas if it is only visible on CT then it is termed occult pneumomediastinum 8.

Aetiology

Although it is rare, pneumomediastinum can occur spontaneously. This is considered benign and generally affects young adult males 9,10.

Small amounts of air appear as linear or curvilinear lucencies outlining mediastinal contours such as:

Paediatric pneumomediastinum may have slightly different appearances:

  • elevated thymus: thymic wing sign
  • air crossing the superior mediastinum: haystack sign (the heart appears like a haystack in Monet's paintings)

Must be distinguished most importantly from:

For small air collections on a CT scan, also consider 3:

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Article Information

rID: 4653
Systems: Chest, Trauma
Section: Pathology
Synonyms or Alternate Spellings:
  • Occult pneumomediastinum
  • Overt pneumomediastinum

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Cases and Figures

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    Case 9: with widespread subcutaneous emphysema
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