''Continuous diaphragm sign'' in pneumomediastinum. The mechanism of its occurrence

The cardiophrenic space, traditionally used the space between the base of pericardium and diaphragm, is actually a closed space fixed by the phrenicopericardial ligament; thus, air is difficult to enter into this space. Newly proposed anatomical space, ''phrenicopericardial recess'' exists around lateral and posterior portion of the heart which is consisted of nearly fatty tissue. ''continuous diaphragm sign'' may be formed by a sharply-peaked air in ''phrenicopericardial recess''. (author)