My 11 yr old son was diagnosed with mediastinal emphysema due to air leak, what are possible causes?

Pneumomediastinum?: Please clarify if the air leak happened in the mediastinum or into the pleural space? The former is called pneumomediastinum & is seen in patients with asthma & other obstructive lung disorders, while the latter would be a pneumothorax & it has several causes. In most cases former resolves slowly as air gets resorbed. The latter requires more evaluation & treatment depending on size of air leak.