Presentations

Abstract

Introduction: Pneumomediastinum is a generally uncommon entity, reportedly occurring in approximately 1/44,500 accidental and emergency attendances, and refers to air or other gases tracking into the mediastinum. There are multiple possible etiologies for this condition including posttraumatic, atraumatic, iatrogenic, and idiopathic causes. Not only are there multiple causes of pneumomediastinum, but there are also numerous sources of air/gas. For example, there may be a direct air leak into the mediastinum related to perforation of the larynx, trachea, bronchus, or esophagus. Alternatively, in the setting of rapidly increasing intrathoracic pressure, alveolar rupture may occur where gas dissects along the bronchovascular sheaths and spread into the mediastinum, commonly referred to as the "Macklin Effect". Still other sources including extension from the abdominal cavity via the diaphragmatic hiatus in the setting of perforated hollow abdominal viscera or along the fascial planes of the neck in the setting of facial trauma have been described. Pneumomediastinum in and of itself is often inconsequential and self-limited but can be the first signs of more serious etiology such as esophageal injury which can progress to life threatening complications. Diagnosis of pneumomediastinum can be made on ultrasound or conventional chest radiography, however relatively large volume is necessary to be seen on these modalities and thus most frequently identified on computed tomography (CT) imaging. Once identified, most patients will undergo fluoroscopic contrast esophagram or CT esophagram to evaluate for esophageal injury.

Case Information: Patient is a 71-year-old female with past medical history of hypertension and diabetes who presented to emergency department after presumed ground level fall with unknown down time. . Following standard trauma protocols, this patient underwent CT of the Chest, Abdomen, and Pelvis which was largely negative except for numerous small locules of gas tracking along the intercostal space, the posterior mediastinum, and into the central spinal canal. There were also subtle anterior endplate deformities of the T7 and T8 vertebral bodies raising the question of vertebral body fractures with possible esophageal injury from the fragments. Patient's initial hospital course was complicated by concerns for ischemic stroke and altered mentation. Stroke work up was negative. Patient underwent limited fluoroscopic esophagram which demonstrated no evidence of esophageal perforation and then subsequently underwent CT esophagram, which was also limited but did not definitively show an underlying injury. Patient reportedly remained asymptomatic during their hospital course, and no subsequent imaging has been performed.

Discussion/Clinical Findings: While pneumomediastinum can be seen as an incidental and self-limited finding, evaluation to rule out potential devastating sources such as esophageal injury is often necessary. Fluoroscopic esophagram performed with water soluble contrast has long been the gold standard for radiological evaluation of esophageal injury, however evaluations can often be limited secondary to patient condition (unable to stand, difficult to appropriately position, challenges complying with swallowing on command, etc) and requires direct involvement of a radiologist or other trained fluoroscopist and a radiology technologist to perform the exam. CT esophagram has been shown in multiple trials to be at least equal too, if not superior to, fluoroscopy in the evaluation of esophageal injury. Additionally, CT esophragram has shown to be better at predicting which cases would require intervention versus conservative management in a relatively small trial, as well as other diagnostically beneficial information. Nonetheless, CT esophragram is not without technical challenges as patient still needs to be relatively compliant and able to swallow on cue for optimal evaluation. Furthermore, the possibility of aspiration and subsequent negative sequala must be considered for both exams. Lastly, as CT esophagram is relatively new, one must consider that there may not be a standard protocol, there is variable acceptance among ordering providers, and there may be differences in interpretation among users.

Conclusion: In conclusion, this is an interesting case of pneumomediastinum because of the lack of clear source or etiology. While the evaluations for esophageal injury were both somewhat limited; the otherwise negative exams, the lack of progression during hospitalization, and the relatively minor trauma may support an alternative etiology. The classic case scenario for spontaneous pneumomediastinum involves younger patients, typically thin, tall, males. Spontaneous pneumomediastinum is generally thought uncommon in the elderly given differences in physiology. However, could this be an atypical case of the "Macklin" effect, or self-limiting esophageal injury. Unfortunately, a definitive explanation is unlikely to be reached.