Spinnaker sign in a c/o pneumomediastinum.

Radiographic signs of pneumomediastinum:

·        Radiolucent streaks representing free gas may be observed vertically (tracking the left side of the heart), retrosternally, precardiac, or surrounding the trachea. Typical features of PM seen on chest radiography caused by air outlining normal anatomic structures as it tracks from the mediastinum include the thymic sail sign, \"ring around the artery\" sign, tubular artery sign, double bronchial wall sign, continuous diaphragm sign, and the extrapleural sign.

·        Ring around the artery (tubular artery): A radiolucent area is observed surrounding the right pulmonary artery when viewed on a lateral chest radiograph.

·        Thymic sail (spinnaker) sign: In infants with PM, the thymic lobes are shifted upwards resembling a full spinnaker.

·        Continuous diaphragm sign: Gas is present between the pericardium and diaphragm, causing the central parts of the diaphragm to become apparent.

 

·        On the lateral exam this air will result in visualization of the entire left hemidiaphram (normally obscured by the heart).