IS case 465: Spinnaker sign in pneumomediastinum
Imaging Sciences URMC 2010
Publication Date: 2010-08-30
History
Patient is a 14-year-old female with ventricular septal defect status post patch closure and patent foramen ovale status post suture closure earlier in the day. There were no immediate post-surgical complications and the patient was stable. Examination was requested to evaluate for line placement.
Findings
Chest radiograph demonstrated an enlarged heart and shunt vascularity. There was a small right apical pneumothorax. Pneumomediastinum is manifest by two findings: a lucent stripe along the border of the right atrium, and adjacent to the pulmonary artery, a thin lucent line elevating a soft tissue structure that is likely the thymus.
Diagnosis
Spinnaker sign in pneumomediastinum
Discussion
Pneumomediastinum can be directly caused by instrumentation, trauma or esophageal perforation, and most commonly secondary to mechanisms of injury causing alveolar rupture. These causes include airway obstruction, positive pressure ventilation, trauma to the lungs, coughing, vomiting, or valsalva performed during exertion. Rupture of alveoli enables air to dissect through the interstitium centrally to the hila and into the mediastinum. In the same manner, air can enter the mediastinal space from the head, neck and abdomen secondary to trauma, instrumentation or perforated viscus.
Pneumomediastinum may produce worrisome complications. The mediastinal pleura may be distended to the point of rupture, causing a pneumothorax. Also if air pressure exceeds the pressure in the right heart, tamponade physiology may ensue.
Radiographic findings usually include a lucent strip of gas outlining the normal cardiac and mediastinal silhouette, and may involve the diaphragm ("continuous diaphragm sign"). Gas may outline the descending aorta ("Naclerio's V-sign"), the confluence of the brachiocephalic veins ("V-sign"), the extrapericardial right pulmonary artery ("the ring-around-the-artery sign").
In children, air in the mediastinum may outline an additional structure not commonly present in adults -- the thymus. Air may outline the thymus and cause it to elevate so that it is viewed as separate from the heart. The characteristic appearance has been called the "spinnaker sign" for the resemblance of the uplifted thymus to an open spinnaker sail.
References
- Bevjan SM, Godwin JD. Pneumomediastinum: old signs and new signs. AJR Am J Roentgenol. 1996 May;166(5):1041-8. PMID: 8615238
- Moseley JE. Loculated pneumomediastinum in the newborn. A thymic “spinnaker sail” sign. Radiology. 1960 Nov;75:788-90. PMID: 13773025
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