Case Report Author:Jeff Rhodes, MSIV Date:24 August, 2010 Radiological Category:Principal Modality (1): Principal Modality (2): Trauma CT General Radiography

Case History JB is a 30 year old male who presented to Hermann Emergency Department after moderate speed motor vehicle collision in which he was an unrestrained passenger vs. an 18 wheeler truck. He had multiple injuries involving the face, extremities, and pelvis. He did have loss of consciousness at the scene, but was conscious on arrival. No known past medical history.

Radiological Presentations

Widened right paratracheal stripe Abnormal contour of left paraspinal line Loss of contour of descending aorta

MOST COMMON: False positive, especially on portable AP films Associated with trauma: Vascular insult/hematoma Esophageal rupture Non-traumatic: Aortic aneurysm Anterior masses: thyroid CA/goiter, thymus/thymoma, lymphadenopathy, germ cell tumor Posterior masses: neurogenic tumors, lymphadenopathy Most common causes of a widened mediastinum: Differential Diagnosis

1. widened mediastinum (>8cm at aortic arch, or subjective) 2. irregularity or obstruction of aortic arch margin 3. deviation of trachea to the right of the T4 spinous process 4. deviation of an NG tube to the right of the T4 spinous process 5. left apical cap 6. depression of left main stem bronchus (>40 o below the horizontal ) 7. widening of left paraspinal interface (>5mm) 8. widening of right paraspinal interface (subjective) 9. loss of contour of descending aorta 10. thickening of right paratracheal stripe (>4mm) ***Negative predictive value of normal chest radiograph is 96% for supine views and 98% for erect views. Signs of mediastinal hematoma on chest radiograph

Chest CT with contrast What radiographic study do you want to order next?? Next Step

Radiological Presentations

There is an outpouching of the descending aorta distal to the left subclavian artery measuring 4.6 cm in the craniocaudal dimension consistent with a traumatic pseudoaneurysm. Mediastinal hematoma is also noted surrounding the aortic arch and descending aorta. There are bilateral pleural fluid collections, left greater than right, consistent with hemothoraces Other findings that are not shown and will not be discussed: pericardial fluid which may represent hemopericardium; hypodense area near porta hepatis consistent with grade 3 liver laceration; right lateral nondisplaced sixth rib fracture; mildly displaced left anterior seventh rib fracture CT Findings

Definition: a pseudoaneurysm forms when the intima and media are ruptured, but the adventitia remains intact, resulting in an outpouching of the aorta. Traumatic aortic pseudoaneurysm with mediastinal hematoma Diagnosis

Trauma commonly resulting in thoracic aortic injury: rapid deceleration injury and crushing chest injury Several forces may contribute to aortic injury: - shearing stress: aortic arch is relatively mobile and the descending aorta is fixed, so they decelerate at different rates - bending stress: occurs with flexion of the aorta over the left pulmonary artery and left main-stem bronchus - osseous pinch theory: aorta is squeezed between anterior bony structures (manubrium, clavicle, first rib) and the spine posteriorly - water-hammer effect: sudden increase in intra-aortic pressure which may cause rupture into the pericardium Discussion

Relationship between mediastinal hematoma and aortic injury - Aortic injury is the cause of mediastinal hematoma in only 12.5% of cases. - Usually, mediastinal hematoma is not directly caused by aortic injury - In these cases, hematoma is formed due to rupture of smaller vessels in the mediastinum. Discussion

Interrelationships of various structures in the lung, mediastinum, and pleura form several recognizable “lines and stripes” that may appear on a normal chest radiograph. Abnormal appearance of any of these warrants further investigation. They include: -Anterior and posterior junction lines -Right and left paratracheal stripes -Aortic-pulmonary stripe -Aortopulmonary window -Right and left paraspinal lines -Posterior tracheal stripe -Azygoesophageal recess -Posterior wall of the bronchos intermedius Lines and Stripes

Right paratracheal stripe – formed by lateral border of trachea, adjacent mediastinal fat, and pleura of right upper lobe outlined by air in the trachea and in the right lung. Normally no more than 4mm. Present in most normal radiographs. Lines and Stripes Most common causes of abnormal right paratracheal stripe: -pleural disease -lymphadenopathy -thyroid or parathyroid neoplasms -tracheal carcinoma or stenosis -hematoma

Lines and Stripes

Radiological Presentations Widened right paratracheal stripe

Left paraspinal line – formed by contact of the left lung and pleura with posterior mediastinal fat, left paraspinal muscles, and adjacent soft tissues. It extends from aortic arch to the diaphragm. Lines and Stripes Most common causes of abnormal left paraspinal line: - osteophytes - prominent mediastinal fat - tortuous descending aorta - mediastinal hematoma - mass - esophageal varices

Lines and Stripes

Radiological Presentations Abnormal contour of left paraspinal line

9 days s/p stent placement

Gibbs JM, Chandrasekhar CA, Ferguson EC, Oldham SA. Lines and Stripes: Where Did They Go? – From Conventional Radiography to CT. Radiographics January-February 2007; 27: Creasy JD, Chiles C, Routh WD, Dyer RB. Overview of traumatic injury of the thoracic aorta. Radiographics January 1997; 17: Herring, William. Learning radiology. Philadelphia, PA: Mosby, Print References