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Pneumomediastinum Revisited¹

¹ From the Department of Radiology, University of Arizona, 1718 E Speedway, PMB 108, Tucson, AZ 85719. Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received April 1, 1999; revision requested May 17 and received July 15; accepted July 15. Address correspondence to C.M.Z. (e-mail: cmzjz@hotmail.com).

View larger version (55K): [in a new window]   Figure 1.   Diagram shows the anterior (A), middle (M), and posterior (P) divisions of the mediastinum proposed in the Zylak method.

View larger version (111K): [in a new window]   Figure 2a.   Spontaneous pneumomediastinum and pneumothorax in a 79-year-old woman with carcinoma of the right upper lobe. (a) Anteroposterior radiograph clearly depicts air extending into the retroperitoneal compartment and outlining the kidney and the retroperitoneal segment of the descending colon. (b) Axial CT scan demonstrates air in the left-sided chest wall and in the mediastinum outlining the vessels. The esophagus is also seen. (c) Axial CT scan demonstrates a left-sided pneumothorax. (d) Axial CT scan shows extension of the pneumothorax into the retroperitoneum and the soft tissues of the thigh.

View larger version (85K): [in a new window]   Figure 2b.   Spontaneous pneumomediastinum and pneumothorax in a 79-year-old woman with carcinoma of the right upper lobe. (a) Anteroposterior radiograph clearly depicts air extending into the retroperitoneal compartment and outlining the kidney and the retroperitoneal segment of the descending colon. (b) Axial CT scan demonstrates air in the left-sided chest wall and in the mediastinum outlining the vessels. The esophagus is also seen. (c) Axial CT scan demonstrates a left-sided pneumothorax. (d) Axial CT scan shows extension of the pneumothorax into the retroperitoneum and the soft tissues of the thigh.

View larger version (75K): [in a new window]   Figure 2c.   Spontaneous pneumomediastinum and pneumothorax in a 79-year-old woman with carcinoma of the right upper lobe. (a) Anteroposterior radiograph clearly depicts air extending into the retroperitoneal compartment and outlining the kidney and the retroperitoneal segment of the descending colon. (b) Axial CT scan demonstrates air in the left-sided chest wall and in the mediastinum outlining the vessels. The esophagus is also seen. (c) Axial CT scan demonstrates a left-sided pneumothorax. (d) Axial CT scan shows extension of the pneumothorax into the retroperitoneum and the soft tissues of the thigh.

View larger version (64K): [in a new window]   Figure 2d.   Spontaneous pneumomediastinum and pneumothorax in a 79-year-old woman with carcinoma of the right upper lobe. (a) Anteroposterior radiograph clearly depicts air extending into the retroperitoneal compartment and outlining the kidney and the retroperitoneal segment of the descending colon. (b) Axial CT scan demonstrates air in the left-sided chest wall and in the mediastinum outlining the vessels. The esophagus is also seen. (c) Axial CT scan demonstrates a left-sided pneumothorax. (d) Axial CT scan shows extension of the pneumothorax into the retroperitoneum and the soft tissues of the thigh.

View larger version (130K): [in a new window]   Figure 3a.   Traumatic pneumomediastinum in a 15-year-old boy who sustained blunt trauma to the thorax following sudden deceleration while skiing. (a) Initial radiograph demonstrates a linear band of mediastinal air paralleling the descending aorta. Extensive consolidation is present in both lungs and represents contusion. Note the medial pneumothorax and the air collection paralleling the left hemidiaphragm, which could represent pneumothorax or extrapleural air. (b) On an anteroposterior radiograph obtained 21 months later, the left hilum remains lower than the right. There is disparity between the two lungs in terms of the number of vessels per unit area. In addition, careful inspection of the major airway reveals a more vertical orientation of the left main bronchus as well as occlusion of the left lower lobe bronchus. (c) Bronchogram demonstrates similar findings, thereby helping confirm the diagnosis (cf a and b). (Courtesy of the Department of Radiology, University of Calgary, Foothills Hospital, Calgary, Alberta, Canada.)

View larger version (137K): [in a new window]   Figure 3b.   Traumatic pneumomediastinum in a 15-year-old boy who sustained blunt trauma to the thorax following sudden deceleration while skiing. (a) Initial radiograph demonstrates a linear band of mediastinal air paralleling the descending aorta. Extensive consolidation is present in both lungs and represents contusion. Note the medial pneumothorax and the air collection paralleling the left hemidiaphragm, which could represent pneumothorax or extrapleural air. (b) On an anteroposterior radiograph obtained 21 months later, the left hilum remains lower than the right. There is disparity between the two lungs in terms of the number of vessels per unit area. In addition, careful inspection of the major airway reveals a more vertical orientation of the left main bronchus as well as occlusion of the left lower lobe bronchus. (c) Bronchogram demonstrates similar findings, thereby helping confirm the diagnosis (cf a and b). (Courtesy of the Department of Radiology, University of Calgary, Foothills Hospital, Calgary, Alberta, Canada.)

View larger version (127K): [in a new window]   Figure 3c.   Traumatic pneumomediastinum in a 15-year-old boy who sustained blunt trauma to the thorax following sudden deceleration while skiing. (a) Initial radiograph demonstrates a linear band of mediastinal air paralleling the descending aorta. Extensive consolidation is present in both lungs and represents contusion. Note the medial pneumothorax and the air collection paralleling the left hemidiaphragm, which could represent pneumothorax or extrapleural air. (b) On an anteroposterior radiograph obtained 21 months later, the left hilum remains lower than the right. There is disparity between the two lungs in terms of the number of vessels per unit area. In addition, careful inspection of the major airway reveals a more vertical orientation of the left main bronchus as well as occlusion of the left lower lobe bronchus. (c) Bronchogram demonstrates similar findings, thereby helping confirm the diagnosis (cf a and b). (Courtesy of the Department of Radiology, University of Calgary, Foothills Hospital, Calgary, Alberta, Canada.)

View larger version (156K): [in a new window]   Figure 4a.   Traumatic pneumomediastinum in a patient who was struck in the face with a baseball bat. (a) Preoperative anteroposterior radiograph surprisingly demonstrates pneumomediastinum outlining the left subclavian artery and possibly the left carotid artery (tubular artery sign). (b) Lateral radiograph demonstrates the "ring around the artery" sign. (c) Axial CT scan demonstrates evidence of extensive trauma to the sinus regions, with fracture of both the anterior and posterior walls of the left maxillary sinus. This injury was believed to be the source of the pneumomediastinum.

View larger version (141K): [in a new window]   Figure 4b.   Traumatic pneumomediastinum in a patient who was struck in the face with a baseball bat. (a) Preoperative anteroposterior radiograph surprisingly demonstrates pneumomediastinum outlining the left subclavian artery and possibly the left carotid artery (tubular artery sign). (b) Lateral radiograph demonstrates the "ring around the artery" sign. (c) Axial CT scan demonstrates evidence of extensive trauma to the sinus regions, with fracture of both the anterior and posterior walls of the left maxillary sinus. This injury was believed to be the source of the pneumomediastinum.

View larger version (125K): [in a new window]   Figure 4c.   Traumatic pneumomediastinum in a patient who was struck in the face with a baseball bat. (a) Preoperative anteroposterior radiograph surprisingly demonstrates pneumomediastinum outlining the left subclavian artery and possibly the left carotid artery (tubular artery sign). (b) Lateral radiograph demonstrates the "ring around the artery" sign. (c) Axial CT scan demonstrates evidence of extensive trauma to the sinus regions, with fracture of both the anterior and posterior walls of the left maxillary sinus. This injury was believed to be the source of the pneumomediastinum.

View larger version (129K): [in a new window]   Figure 5.   Traumatic pneumomediastinum in a patient who had sustained a gunshot injury. Anteroposterior radiograph obtained 9 days after exploration and repair of the duodenum, right kidney, and liver demonstrates elevation of the pleura away from the left pulmonary artery and ascending aorta secondary to air in the mediastinum.

View larger version (112K): [in a new window]   Figure 6a.   Pneumomediastinum in a 44-year-old man who had donated the left kidney. Anteroposterior (a) and lateral (b) radiographs obtained 1 day after organ donation show streaks of air within the mediastinal fat, producing a rather bizarre appearance.

View larger version (125K): [in a new window]   Figure 6b.   Pneumomediastinum in a 44-year-old man who had donated the left kidney. Anteroposterior (a) and lateral (b) radiographs obtained 1 day after organ donation show streaks of air within the mediastinal fat, producing a rather bizarre appearance.

View larger version (197K): [in a new window]   Figure 7a.   Pneumomediastinum due to alveolar rupture. (a) Photograph of a resected lung specimen from a cat that had undergone intratracheal insufflation with air to pressures of 100 cm of water demonstrates interstitial emphysema, which manifests as air in the sheaths surrounding the pulmonary artery (a) and vein (v). b = bronchus. (Reprinted, with permission, from reference 6.) (b) Photograph of a resected lung specimen from a dog that had undergone insufflation at similar pressures again demonstrates air surrounding only the vessels. (c) Photomicrograph of tissue obtained from the dog demonstrates air in a perivenous space. (Fig 7b, 7c courtesy of Lee Rogers, MD.)

View larger version (164K): [in a new window]   Figure 7b.   Pneumomediastinum due to alveolar rupture. (a) Photograph of a resected lung specimen from a cat that had undergone intratracheal insufflation with air to pressures of 100 cm of water demonstrates interstitial emphysema, which manifests as air in the sheaths surrounding the pulmonary artery (a) and vein (v). b = bronchus. (Reprinted, with permission, from reference 6.) (b) Photograph of a resected lung specimen from a dog that had undergone insufflation at similar pressures again demonstrates air surrounding only the vessels. (c) Photomicrograph of tissue obtained from the dog demonstrates air in a perivenous space. (Fig 7b, 7c courtesy of Lee Rogers, MD.)

View larger version (185K): [in a new window]   Figure 7c.   Pneumomediastinum due to alveolar rupture. (a) Photograph of a resected lung specimen from a cat that had undergone intratracheal insufflation with air to pressures of 100 cm of water demonstrates interstitial emphysema, which manifests as air in the sheaths surrounding the pulmonary artery (a) and vein (v). b = bronchus. (Reprinted, with permission, from reference 6.) (b) Photograph of a resected lung specimen from a dog that had undergone insufflation at similar pressures again demonstrates air surrounding only the vessels. (c) Photomicrograph of tissue obtained from the dog demonstrates air in a perivenous space. (Fig 7b, 7c courtesy of Lee Rogers, MD.)

View larger version (133K): [in a new window]   Figure 8a.   Pneumomediastinum in a 41-year-old woman with pneumonia who required ventilation with positive end-expiratory pressure. Axial CT scans show pneumomediastinum (a) and air in the perivascular and peribronchial sheaths (b) (arrows). (Courtesy of J.P. Locksmith, MD, Medical College of Georgia, Augusta.)

View larger version (138K): [in a new window]   Figure 8b.   Pneumomediastinum in a 41-year-old woman with pneumonia who required ventilation with positive end-expiratory pressure. Axial CT scans show pneumomediastinum (a) and air in the perivascular and peribronchial sheaths (b) (arrows). (Courtesy of J.P. Locksmith, MD, Medical College of Georgia, Augusta.)

View larger version (143K): [in a new window]   Figure 9a.   Thymic sail sign in a 4-year-old patient who had inhaled gasoline fumes. (a) Initial anteroposterior radiograph demonstrates findings consistent with pulmonary edema. (b) Anteroposterior radiograph obtained 50 minutes later shows air in the subcutaneous tissues of the neck, a finding that is consistent with pneumomediastinum. The thymus is outlined by air (thymic sail sign). However, there is also a well-defined opaque line paralleling the left border of the heart and extending to the level of the pulmonary artery that represents the pericardium. (c) Anteroposterior radiograph clearly depicts the tube that was inserted into the pericardium and helped successfully relieve the tamponade. The patient made an uneventful recovery.

View larger version (136K): [in a new window]   Figure 9b.   Thymic sail sign in a 4-year-old patient who had inhaled gasoline fumes. (a) Initial anteroposterior radiograph demonstrates findings consistent with pulmonary edema. (b) Anteroposterior radiograph obtained 50 minutes later shows air in the subcutaneous tissues of the neck, a finding that is consistent with pneumomediastinum. The thymus is outlined by air (thymic sail sign). However, there is also a well-defined opaque line paralleling the left border of the heart and extending to the level of the pulmonary artery that represents the pericardium. (c) Anteroposterior radiograph clearly depicts the tube that was inserted into the pericardium and helped successfully relieve the tamponade. The patient made an uneventful recovery.

View larger version (129K): [in a new window]   Figure 9c.   Thymic sail sign in a 4-year-old patient who had inhaled gasoline fumes. (a) Initial anteroposterior radiograph demonstrates findings consistent with pulmonary edema. (b) Anteroposterior radiograph obtained 50 minutes later shows air in the subcutaneous tissues of the neck, a finding that is consistent with pneumomediastinum. The thymus is outlined by air (thymic sail sign). However, there is also a well-defined opaque line paralleling the left border of the heart and extending to the level of the pulmonary artery that represents the pericardium. (c) Anteroposterior radiograph clearly depicts the tube that was inserted into the pericardium and helped successfully relieve the tamponade. The patient made an uneventful recovery.

View larger version (148K): [in a new window]   Figure 10a.   Pneumomediastinum in an 18-year-old asthmatic patient who presented with shortness of breath and sternal discomfort. (a) Anteroposterior radiograph demonstrates the continuous diaphragm sign. (b) Lateral radiograph shows air surrounding the right pulmonary artery (ring around the artery sign). Air is present anterior to the pericardium (pneumoprecardium).

View larger version (138K): [in a new window]   Figure 10b.   Pneumomediastinum in an 18-year-old asthmatic patient who presented with shortness of breath and sternal discomfort. (a) Anteroposterior radiograph demonstrates the continuous diaphragm sign. (b) Lateral radiograph shows air surrounding the right pulmonary artery (ring around the artery sign). Air is present anterior to the pericardium (pneumoprecardium).

View larger version (121K): [in a new window]   Figure 11a.   Tubular artery sign in a 28-year-old man who sustained blunt trauma. (a) Anteroposterior radiograph demonstrates an air-fluid level projecting at the left costophrenic angle surrounded by increased airspace opacity. These findings represent a laceration with surrounding contusion. The tubular structure seen arising from the top of the aorta represents displacement of the left subclavian artery by air in the mediastinum. The mediastinal air outlines the medial side of the artery, and the aerated lung marginates its lateral border. The left common carotid artery is also faintly visible. (b) Follow-up radiograph obtained 27 days later demonstrates resolution of the pneumomediastinum and lung contusion. The resolving pneumatocele is now readily apparent.

View larger version (119K): [in a new window]   Figure 11b.   Tubular artery sign in a 28-year-old man who sustained blunt trauma. (a) Anteroposterior radiograph demonstrates an air-fluid level projecting at the left costophrenic angle surrounded by increased airspace opacity. These findings represent a laceration with surrounding contusion. The tubular structure seen arising from the top of the aorta represents displacement of the left subclavian artery by air in the mediastinum. The mediastinal air outlines the medial side of the artery, and the aerated lung marginates its lateral border. The left common carotid artery is also faintly visible. (b) Follow-up radiograph obtained 27 days later demonstrates resolution of the pneumomediastinum and lung contusion. The resolving pneumatocele is now readily apparent.

View larger version (109K): [in a new window]   Figure 12a.   Double bronchial wall sign. (a) Radiograph obtained in a 35-year-old asthmatic patient demonstrates air in the mediastinum and left main bronchus, which allows visualization of both sides of the bronchial wall. (b) Axial CT scan obtained in a different patient helps explain this sign. Air in the mediastinum outlines the posterior aspect of the inferior wall of the left mainstem bronchus, whereas air in the bronchus outlines its anterior surface.

View larger version (92K): [in a new window]   Figure 12b.   Double bronchial wall sign. (a) Radiograph obtained in a 35-year-old asthmatic patient demonstrates air in the mediastinum and left main bronchus, which allows visualization of both sides of the bronchial wall. (b) Axial CT scan obtained in a different patient helps explain this sign. Air in the mediastinum outlines the posterior aspect of the inferior wall of the left mainstem bronchus, whereas air in the bronchus outlines its anterior surface.

View larger version (115K): [in a new window]   Figure 13.   Extrapleural sign in a 26-year-old woman with esophageal rupture. Anteroposterior radiograph demonstrates a linear area of lucency paralleling the descending aorta (arrow) representing air within the mediastinum. A collection of air is seen just lateral to the lower descending aorta (black arrowheads). This air presumably resides within the pulmonary ligament. Note also the small collection of air in the left pleural space (white arrowheads).

View larger version (136K): [in a new window]   Figure 14a.   Pseudomediastinum in a 78-year-old woman who underwent endoscopic dilation of an esophageal stricture. The patient developed chest pain following the procedure. (a) CT digital radiograph demonstrates extravasation of barium into the mediastinum. (b) Axial CT scan shows mediastinal air outlining the descending aorta. Note the paraesophageal collection of contrast material in the pulmonary ligament (arrow). (c) CT scan demonstrates a collection of contrast material extending over the hemidiaphragm (arrow). The extrapleural location was confirmed at surgery.

View larger version (96K): [in a new window]   Figure 14b.   Pseudomediastinum in a 78-year-old woman who underwent endoscopic dilation of an esophageal stricture. The patient developed chest pain following the procedure. (a) CT digital radiograph demonstrates extravasation of barium into the mediastinum. (b) Axial CT scan shows mediastinal air outlining the descending aorta. Note the paraesophageal collection of contrast material in the pulmonary ligament (arrow). (c) CT scan demonstrates a collection of contrast material extending over the hemidiaphragm (arrow). The extrapleural location was confirmed at surgery.

View larger version (130K): [in a new window]   Figure 14c.   Pseudomediastinum in a 78-year-old woman who underwent endoscopic dilation of an esophageal stricture. The patient developed chest pain following the procedure. (a) CT digital radiograph demonstrates extravasation of barium into the mediastinum. (b) Axial CT scan shows mediastinal air outlining the descending aorta. Note the paraesophageal collection of contrast material in the pulmonary ligament (arrow). (c) CT scan demonstrates a collection of contrast material extending over the hemidiaphragm (arrow). The extrapleural location was confirmed at surgery.

View larger version (106K): [in a new window]   Figure 15a.   Medial pneumothorax. (a) Anteroposterior radiograph demonstrates a left-sided medial pneumothorax with placement of a catheter aspiration tube for simple pneumothorax. Prior radiographs (not shown) demonstrated total collapse of the left lung. (b) On an anteroposterior radiograph obtained 1 day later, the residual medial pneumothorax (arrow) is very difficult to distinguish from pneumomediastinum.

View larger version (100K): [in a new window]   Figure 15b.   Medial pneumothorax. (a) Anteroposterior radiograph demonstrates a left-sided medial pneumothorax with placement of a catheter aspiration tube for simple pneumothorax. Prior radiographs (not shown) demonstrated total collapse of the left lung. (b) On an anteroposterior radiograph obtained 1 day later, the residual medial pneumothorax (arrow) is very difficult to distinguish from pneumomediastinum.

View larger version (108K): [in a new window]   Figure 16a.   Spontaneous pneumothorax in a 22-year-old man. (a) On an anteroposterior radiograph, the configuration of the heart is unusual in that the left ventricle extends quite far laterally. A linear band of air is seen paralleling the right border of the heart and terminating abruptly near the hilum (arrow). Air is seen outlining the main and right pulmonary arteries. These findings suggest a partial congenital pericardial defect that allows communication between the pleural and pericardial sacs. (b) Lateral radiograph demonstrates the ring around the artery sign. (Courtesy of the Department of Radiology, University of Calgary, Foothills Hospital, Calgary, Alberta, Canada.)

View larger version (132K): [in a new window]   Figure 16b.   Spontaneous pneumothorax in a 22-year-old man. (a) On an anteroposterior radiograph, the configuration of the heart is unusual in that the left ventricle extends quite far laterally. A linear band of air is seen paralleling the right border of the heart and terminating abruptly near the hilum (arrow). Air is seen outlining the main and right pulmonary arteries. These findings suggest a partial congenital pericardial defect that allows communication between the pleural and pericardial sacs. (b) Lateral radiograph demonstrates the ring around the artery sign. (Courtesy of the Department of Radiology, University of Calgary, Foothills Hospital, Calgary, Alberta, Canada.)

View larger version (111K): [in a new window]   Figure 17.   Subpulmonary pneumothorax. Anteroposterior radiograph shows a right subpulmonary pneumothorax mimicking an extrapleural collection of air.

View larger version (106K): [in a new window]   Figure 18a.   Pneumoperitoneum. (a) Anteroposterior radiograph demonstrates pneumoperitoneum simulating extrapleural and subpulmonary air collections. (b) CT scan helps confirm the intraperitoneal location of the air. Note also the extensive subcutaneous emphysema and the air extending from the mediastinum into the retroperitoneum.

View larger version (95K): [in a new window]   Figure 18b.   Pneumoperitoneum. (a) Anteroposterior radiograph demonstrates pneumoperitoneum simulating extrapleural and subpulmonary air collections. (b) CT scan helps confirm the intraperitoneal location of the air. Note also the extensive subcutaneous emphysema and the air extending from the mediastinum into the retroperitoneum.

View larger version (94K): [in a new window]   Figure 19.   Major fissure simulating disease. Radiograph demonstrates the superior aspect of a major fissure simulating pneumomediastinum or medial pneumothorax (arrows). This finding was confirmed at fluoroscopy.

View larger version (116K): [in a new window]   Figure 20.   Anterior junction line simulating pneumomediastinum. Radiograph obtained with the patient in a somewhat lordotic position demonstrates the normal anterior junction line (arrows).

View larger version (147K): [in a new window]   Figure 21.   Mach band effect. Anteroposterior radiograph demonstrates the Mach band effect adjacent to the descending aorta.

View larger version (115K): [in a new window]   Figure 22a.   Iatrogenic simulation of pneumomediastinum due to helium in an intraaortic balloon assist device. (a) Anteroposterior radiograph obtained in a cardiac intensive care unit patient demonstrates global cardiomegaly. The metallic tip of an intraaortic balloon assist device is seen projecting just inferior to the aortic knob. A linear area of lucency representing helium in the intraaortic assist device is seen paralleling the spine. (b) Radiograph shows the assist device. The device has been inflated and placed in a container of water, which serves as the surrounding medium.

View larger version (61K): [in a new window]   Figure 22b.   Iatrogenic simulation of pneumomediastinum due to helium in an intraaortic balloon assist device. (a) Anteroposterior radiograph obtained in a cardiac intensive care unit patient demonstrates global cardiomegaly. The metallic tip of an intraaortic balloon assist device is seen projecting just inferior to the aortic knob. A linear area of lucency representing helium in the intraaortic assist device is seen paralleling the spine. (b) Radiograph shows the assist device. The device has been inflated and placed in a container of water, which serves as the surrounding medium.