Diagnosis Reviews based on case series demonstrate that most patients with SPM are young males who present with chest pain or dyspnea as their first or second complaint.1,3,19-21 Chest pain is described as substernal, radiating to the back or neck, and increased by deep inspiration or swallowing. Dysphagia and neck pain are common as well. Physical examination often reveals normal vital signs; occasionally, the examination is entirely normal. Specific findings may include palpable subcutaneous emphysema (with a “bubblewrap” texture) in the neck, decreased cardiac dullness to percussion, and mediastinal crepitation (crunch) with systole (Hamman's sign).1,3,19-21 Most authorities suggest that radiographic findings commonly include air in the mediastinum and subcutaneous air in the soft tissues of the neck.1-3,19-21 These findings are demonstrated on radiographs by linear streaks of gas in the mediastinum extending into the neck, periaortic air, air enveloping the right pulmonary artery, or a continuous diaphragm sign with air interspersed between the pericardium and the diaphragm. Such radiographic patterns are consistent with the pathophysiology of SPM, in that free air would tend to track along the interstitial tissue surrounding the bronchi and blood vessels before possible expansion into the mediastinal spaces.
In some cases, further evaluation with endoscopy and CT may be indicated to evaluate underlying causes of SPM.1-3,19,20 Specifically, tension pneumothorax, ruptured laryngocele, and foreign-body obstruction need to be ruled out when diagnosing SPM.3 Other conditions to consider include pulmonary embolus, panic disorder, exercise-induced bronchospasm, cervical or mediastinal tumors, drug abuse, carotid thrombosis, cervical radiculopathy, and esophageal strictures.1
Management and prognosis Expectant care with supplemental oxygen, reassurance, and analgesics may be all that is required for patients with SPM.1,3,19,20 Typically these patients have been followed with serial radiographs, but the value of repeat films has been questioned because of the condition's benign course.3 Use of antibiotics has been reported but challenged because infection has not been a common sequela of SPM.1 In rare cases, needle decompression of a tension SPM may be required;21 however, most patients do not require any active intervention. While SPM is usually benign and selflimited, progression to fatal pneumomediastinum has been reported, albeit in a patient with dermatomyositis.22 In one case series of 25 patients, 2-year follow-up identified four cases of spontaneous pneumothorax but only one recurrent SPM.1
Conclusion The use of the word spontaneous in the description of SPM has come to include many conditions that do not meet its strict interpretation. There remain a significant number of cases, such as the one presented here, for which precipitating events cannot be or were not identified. These can be classified as idiopathic spontaneous pneumomediastinum. This may be the result of poor history-taking, lack of patient candor (specifically where illicit drugs are involved), or mechanisms yet to be identified. Despite the fact that patients with SPM typically do well, clinicians need to be aware of the life-threatening conditions that are included in the differential diagnosis and must be ruled out, a correlation with illicit drug abuse, and the risks of unnecessary procedures and treatments. JAAPA
David Irvine is program director of the Albany Medical College Physician Assistant Program, Albany, New York. Wilson Crone is a basic science instructor, also in the Albany Medical College Physician Assistant Program. The authors have indicated no relationships to disclose relating to the content of this article.
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