Thymus - Sail Signs
Spinnaker Sail Sign

Normal Thymic Sail Sign

• The thymus is usually composed of two lobes, a right and a left, occasionally fused
• It has a soft consistency and is easily indented by fissures and ribs
• The normal thymic sail sign is usually seen on the right side where the right lobe of the thymus abuts the minor (horizontal) fissure and produces a triangular density next to the trachea
• It does not displace the trachea and is not separated from the trachea of the heart by air density

Spinnaker Sail Sign

• A pathologic finding indicating pneumomediastinum
• The lobe/lobes of the thymus are displaced laterally and superiorly, separated from the heart and mediastinal structures by air in the mediastinum

Imaging Findings

Normal Thymic Sail Sign. The triangular density to the right of the mediastinum is bounded inferiorly by the major fissure and the density is NOT separated from the mediastinum by air.

Spinnaker Sail Sign. This is abnormal. The right and left lobes of the thymus are displaced off of the mediastinal structures by air in the mediastinum. The thymus looks like the spinnaker sails of a ship. There is a also a "continuous diaphragm sign" of pneumomediastinum and bilateral pneumothoraces.

Images in pediatrics: The thymic sail sign and thymic wave sign. Nuno D. Alves & Marta Sousa. Eur J Pediatr (2013) 172:133