CASE STUDY Chris van Zyl KHC

MR X  21 Year old male  Stab wound L parasternally, 3 ICS (sucking wound)  Surgical emphysema extending to neck  Haemodynamically stable,  no signs of tamponade / vascular injury  Mild resp distress, clinically no pneumothorax

CXR

Differential  Pneumomediastinum  Pneumothorax  Haemopericardium  Pneumopericardium

Mr X  Proceded to insert ICD  Consulted Radiology for heart US No haemopericardium seen  Due to location of wound, proceded to CT chest

AXIAL CT CHEST

Sag + Axial neck

THE SIGNS Pneumomediastinum

Introduction  Can be diagnostic challenge  Demonstrate radiological findings that are difficult to differentiate from other disease entities  Needs good understanding of normal anatomy, pathophysiology and radiological signs to meet the challenge

Anatomy  Tissues and organs separating two pleural sacs  Between sternum and vertebral column  Extending from thoracic inlet and diaphragm  Communicates with:  Submandibular space  Retropharyngeal space  Vascular sheaths of the neck

Anatomy  Tissue plane extending anteriorly from mediastinum to retroperitoneal space via diaphraghmatic sternocostal attachment  Continuous along flanks and extends to pelvis  Communicates with peritonium via periaortic and peri-esophageal fascial planes  Air can dissect allong these planes

Potential Sources of Mediastinal Air  Extrathoracic  Head and neck  Intraperitoneum and retroperitoneum  Intrathoracic  Trachea and major bronchi  Esophagus  Lung  Pleural space

Radiographic Signs of Pneumomediastinum  Subcutaneous emphysema  Thymic sail sign  Pneumoprecordium  Ring around the artery sign  Tubular artery sign  Double bronchial wall sign  Continuous diaphragm sign  Extrapleural sign  Air in the pulmonary ligament

Pneumoprecardium

Thymic sail sign

Ring around the artery sign, Tubular artery sign

Double bronchial wall sign

Continuous diaphragm sign

Extrapleural sign

Challenges and Pitfalls  Differentiating pneumomediastinum from medial pneumothorax  Pneumopericardium  Suspect when paricarial sac itself is visualized  Line formed by pneumopericardium confined to lenth of pericardial sac

Pneumopericardium

Chanllenges and Pitfalls  Subpulmonary pneumo + pneumoperitonium can be difficult to defferentiate from extrapleural air collections  Decubitis view helps

Challenges and Pitfalls  Normal anatomic structures can mimic air within mediastinum  Anterior junction line  Imaged obliquely or lordotically  Superior aspect of major fissure  Lordotic positioning

Major fissure

Anterior junction line

Challenges and Pitfalls  Mach band effect  Optical illusion  Region of lucency associated with convex structures

Chanllenges and Pitfalls  Iatrogenic entities

Conclusion  Pneumomediastinum can be a diagnostic challenge  Correct assessment of radiological signs is vital in diagnosis.

REFERENCES  Radiographics Jun – Aug 2000  Pneumomediastinum Revisited