Radiological Category Thoracic Chest Principal Modality 1 General

Radiological Category: Thoracic Chest Principal Modality (1): General Radiography Principal Modality (2): CT Case Report #0617 Submitted by: Miguel Fabrega, M. D. Faculty reviewer: Emma Ferguson, M. D. Date accepted: 11 April 2009

Case History 18 year old male with no significant past medical history, presents with shortness of breath for 2 days.

Radiological Presentations PA radiograph of chest

Radiological Presentations Lateral Radiograph of Chest

Radiological Presentations PA radiograph of Chest, Magnified Area of Interest

Test Your Diagnosis In regards to the magnified area of interest, which one of the following is your choice for the appropriate diagnosis? After your selection, go to next page. • Pneumothorax • Skin Fold • Pneumomediastinum • Lobar Fissure • Mach Band

Findings and Differentials Findings: -Curvilinear opacity roughly paralleling left heart border -Lung markings extend beyond line to lung periphery -Increased retrosternal lucency on lateral view -Increased sharpness of left heart border -On PA view, increased lucency centrally over lower mediastinum extending below the diaphragm -Cuvilinear opacities in peripheral lung apices with strand like markings beyond -Increased lucency in soft tissue planes of the neck Differentials: • Pneumomediastinum • Pneumothorax • Pneumopericardium • Skin fold

Discussion Pneumothorax: With regard to the curvilinear opacity paralleling the left heart border, pneumothorax is unlikely. Although an anterior/medial pneumothorax will increase the sharpness of the left heart border and cause increaed retrosternal lucency, lung markings are clearly seen extending peripheral to the line. However, the curved lines in the apices that conform in shape to the thoracic wall are suspicious for apical pneumothoraces. The appearance is somewhat atypical however, as strandy opacities are seen peripheral to what would be considered the visceral pleural line (yellow arrows on next slide).

Radiological Presentations Magnified PA View of Right Lung Apex

Discussion Skin Fold: Linear or curvilinear opacities with lung markings extending beyond the line are often dismissed as skin folds. In this case, however, many other concurrent findings indicate that the line projected over the left hemithorax is more than just a skin fold. Retrosternal lucencies, abnormalities in lung apices, and air in the soft tissues of the neck indicate a more complex process is occurring. Furthermore, conformity of the line to the contour of the left heart should arouse suspicion.

Discussion Pneumopericardium: Air within the pericardial sac can result in air on both surfaces of the pericardium, which may result in a line that parallels the left heart border. However, it should not be seen above the level of the aortic arch (see next slide).

Radiological Presentations Air in Soft Tissue Planes of Neck, Extending above Aortic Arch

Discussion Pneumomediastinum: Air within the mediastinum can push the pleura away from the heart surface and create a line that parallels the heart border. The heart border itself becomes sharper than expected due to adjacent air. Furthermore, air can dissect from the mediastinum into the cervical soft tissues, into the extrapleural spaces, and inferiorly into the retroperitoneum.

Radiological Presentations Air in the mediastinum displaces the pleura away from the heart surface and creates an additional air/pleura interface medially (yellow arrows). Also, mediastinal air can dissect inferiorly into the retroperitoneum (orange arrows).

Radiological Presentations Axial CT image in the same patient demonstrates mediastinal air.

Radiological Presentations Axial CT image shows para-aortic and paravertebral retroperitoneal air.

Radiological Presentations Air dissecting from the mediastinum into the extrapleural space may create a parietal pleura line with connective tissue strands more peripherally (yellow arrows). Also, air from the mediastinum can enter the cervical soft tissues (orange arrows).

Radiological Presentations Axial CT image in the same patient demonstrates mediastinal air dissecting into the extrapleural space near the lung apices, creating a parietal pleura/air interface and outlining connective tissue strands.

Radiological Presentations Axial CT image shows air in the cervical soft tissues outlining the vascular structures.

Discussion Air from the lungs is the most common source of pneumomediastinum. A sudden rise in intrathoracic pressure (i. e. , blunt trauma, mechanical ventilation, Valsalva) may lead to alveolar rupture, which collects within the bronchovascular interstitium and dissects centrally to the mediastinum (Machlin effect). No specific etiology for pneumomediastinum was discovered for the patient described in this case. Spontaneuous pneumomediastinum can result from Valsalva maneuvers occuring during strenous exercise, childbirth, and inhalation of drugs (crack, cocaine, marijuana). Also, asthmatics are prone to spontaneous pneumothorax. Less common causes of pneumomediastinum include esophageal rupture, fistulous communication with trachea or esophagus, extension from pneumoperitoneum, stab wounds, and laryngeal fracture. It should be noted that pneumomediastinum may result in a pneumothorax as shown, but a pneumothorax will not cause pneumomediastium.

Discussion Tension pneumomediasitnum: a rare complication of pneumomediastinum occurs when sufficient volume or pressure builds up to exert a compressive force on the mediastinum. In this case, it should be considered, as the patients heart is displaced from the anterior chest wall. The patient should be checked for tamponade like symptoms, which is the typical presentation of tension pneumomediastinum.

Radiological Presentations Axial CT image shows the base of the heart displaced from the anterior thoracic wall

Radiological Presentations A B Comparison lateral radiographs of same patient taken at time of presentation (A) and later on during follow up (B). Figure A shows the displacement of the heart posteriorly Figure B shows the patient’s baseline, with the heart flush against the thoracic wall.

Diagnosis Spontaneous pneumomediastinum with associated extrapleural and retroperitoneal air, concerning for tension pneumomediastinum

References 1. Brant WE, Helms CA, eds. Fundamentals of Diagnostic Radiology. 3 rd Edition. PA: Lippincott Williams & Wilkins; 2000: 410 -412. 2. Mirvis SE, Shanmuganathan K, eds. Imaging in Trauma and Critical Care. PA: Saunders; 2003: 301 -302 3. Zylak CM et al. Pneumomediastinum Revisited. Radio. Graphics 2000. 20: 1042 -1057.