Pseudopneumomediastinum

Pseudopneumomediastinum is the false impression, usually on a chest x-ray, of pneumomediastinum. Correctly identifying pneumomediastinum is important, but making the diagnosis in error may lead to further unnecessary investigation and possible treatment.

Causes include:

• Mach band
• superimposed normal structures such as the anterior junctional line or the superior aspect of the left major fissure
• tracheal diverticulum
• subpleural cystic disease such as paraseptal emphysema