Unilateral fractures of the lateral wall of the maxillary sinuses are generally due to direct trauma (either penetrating or blunt). Air within the maxillary sinus escapes into the subcutaneous tissues. If there is an associated fracture of the zygomatic arch (not present in this case), the complex is termed a tripod fracture.
 A | Submentovertical radiograph. This image of the paranasal sinuses reveals extensive subcutaneous emphysema. |
 B | Axial CT. This image through the maxillary sinuses confirms the presence of subcutaneous gas. |
 C | Axial CT. This image through the maxillary sinuses reveals a fracture of the lateral wall of the right maxillary sinus, the source of the emphysema |
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