Pneumomediastinum

Pneumomediastinum is the presence of extraluminal gas within the mediastinum. Gas may originate from the lungs, trachea, central bronchi, esophagus, and 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.

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

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

Pediatric pneumomediastinum may have slightly different appearances:

  • elevated thymus: thymic wing sign
  • gas crossing the superior mediastinum: haystack sign (the heart appears like a haystack in a Monet painting)

Must be distinguished most importantly from:

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

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Article information

rID: 4653
System: Chest, Trauma
Synonyms or Alternate Spellings:
  • Occult pneumomediastinum
  • Overt pneumomediastinum

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Cases and figures

  • Pneumomediastinum
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  • Pneumomediastinum
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  • Case 8: spontaneous
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  • Case 9: with widespread subcutaneous emphysema
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  • Case 15: barotrauma
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  • Case 16: spontaneous
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  • Case 20: annotated
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