Volume 1, Case 7 Answers

Later that morning, a radiologist reading his CXR noted a pneumomediastinum. On the PA film, air is seen dissecting along the superior mediastinum bilaterally, and shadows consistent with subcutaneous emphysema were noted apically over the left lung. Note the vertical air densities extending upward from the mediastinum more noticeable on the left than on the right. There is also air superimposed over the inferior aspect of the aortic arch.

More impressively, the lateral radiograph revealed mediastinal air trapping with thymic demarcation. Note the oblique air space present above (anterior and superior to) the heart. You may have to adjust the brightness and contrast controls on your monitor to visualize these findings. There are also vertical air densities outlining the trachea.

The patient was called to notify him of the findings. His symptoms had resolved. He was instructed to follow up with his private physician.

Teaching points:

1. The abuse of crack cocaine has become epidemic among adolescents in many areas. The possibility of drug abuse in any adolescent who arrives with chest or pulmonary complaints should be considered (1).
2. Abnormal chest radiographs are quite common in cocaine users admitted with respiratory complaints, ranging from 12-55% (2). Both pneumomediastinum and pneumothorax are relatively common after illicit cocaine use, and the incidence is higher for those who smoke crack cocaine, a relatively pure, extremely addictive, intensely euphoric alkaloid form of cocaine. Of those with pneumomediastinum, one series reported 73% with detectable subcutaneous emphysema and 50% with Hamman's sign, an unusual systolic crunch heard over the cardiac apex and the left sternal border (3).

   The mechanism of air leaks is felt to be related to exertional inhalation with Valsalva maneuvers. Drug users do this to accomplish the highest delivery of drug to the bloodstream. Irritants in the inhalant and the higher temperatures of the inhalant may induce reflex coughing, resulting in even greater intrathoracic pressure surges. In most cases, air is allowed into the mediastinum by spontaneous rupture of distended alveoli into the pulmonary vascular sheath (4).

3. The peculiar crackling, bubbling, or churning sounds heard usually during systole (Hamman's sign) are considered, by some, to be pathognomonic for mediastinal emphysema, and were first described in 1945 by Hamman (5), who also attributed interstitial emphysema to trauma, increased intrapulmonary pressure (Valsalva maneuvers and cough), or spontaneous rupture of alveoli. Hamman's sign is often noted to be transient, as in this case. Hamman's sign has also been well described with isolated pneumothoraces and may represent free pleural air cyclically channeled through a lung fissure (6).
4. Retrospective reviews of young children with tracheobronchial foreign body aspiration have revealed a relatively high frequency of pneumomediastinum on initial chest radiographs. The radiographic finding of pneumomediastinum should lead to the consideration of foreign body aspiration in any child in a high risk age group (7,8).
5. Pneumomediastinum is seen not uncommonly as a relatively late complication of cystic fibrosis (9), and if noted in any steroid-dependent child with unexplained fevers, esophageal rupture should be considered (10). Rarely, pneumomediastinum may signal tracheobronchial disruption in any patient with blunt thoracic trauma (11).
6. Pneumomediastinum and/or pneumothorax should be considered as an etiology for respiratory complaints or chest pain in any young person whose daily activities may include an unusual frequency of Valsalva maneuvers or increased intrathoracic pressure. Examples include a young trombonist (12) and a Chinese martial arts expert (13).
7. Complete recovery within days is expected for drug- and Valsalva-related pneumomediastinum.

References:

1. Luque MA, Cavallaro DL, Torres M, Emmanual P, Hillman JV. Pneumomediastinum, pneumothorax, and subcutaneous emphysema after alternate cocaine inhalation and marijuana smoking. Pediatric Emergency Care 1987:3(2): 107-109.
2. McCarroll KA, Roszler MH. Lung disorders due to drug abuse. Journal of Thoracic Imaging 1991:6(1):30-35.
3. Seaman ME. Barotrauma related to inhalational drug abuse. Journal of Emergency Medicine 1990:8(2):141-149.
4. Brody SL, Anderson GV, Gutman JB. Pneumomediastinum as a complication of crack smoking. American Journal of Emergency Medicine 1988:6(3):241-243.
5. Hamman L. Mediastinal emphysema. Journal of the American Medical Association 1945;128:1-6.
6. Baumann MH, Sahn SA. Hamman's sign revisited. Pneumothorax or pneumomediastinum? Chest 1992;102(4):1281-1282.
7. Burton EM, Riggs W Jr, Kaufman RA, Houston CS. Pneumomediastinum Caused by Foreign Body Aspiration in Children. Pediatric Radiology 1989;20(1-2):45-47.
8. Ramadan HH, Bu-Saba N, Baraka A, Mroueh S. Management of an Unusual Presentation of Foreign Body Aspiration. Journal of Laryngology and Otolaryngology. 1992;106(8):751-752.
9. Grum CM, Lynch JP. Chest radiographic findings in cystic fibrosis. Seminars in Respiratory Infections 1992;7(3):192-209.
10. Klygis LM, Jutabha R, McCrohan MB, Vanagunas AD. Esophageal Perforations Masked by Steroids. Abdominal Imaging 1993:18(1):10-12.
11. Baumgartner F, Sheppard B, deVirgilio C, Esrig B, Harrier D, Nelson RJ, Robertson JM. Tracheal and Main Bronchial Disruptions After Blunt Trauma. Annals of Thoracic Surgery 1990;50(4):569-574.
12. Ito S, Takada Y, Tanaka A, Ozeki N, Yazaki Y. A case of spontaneous pneumomediastinum in a trombonist. Kokyu To Junkan 1989;37(12):1359-62.
13. Yoneyama H, Matsushima T, Nakamura J, Yano T, Adachi M, Tano Y. Two cases of spontaneous pneumomediastinum due to Xiao-lin Temple boxing vocal exercise. Nippon Kyobu Shikkan Gakkai Zasshi 1990;28(1):151-155.

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 Loren Yamamoto, 
      MD, MPH Associate Professor of Pediatrics University of Hawaii John A. Burns 
      School of Medicine loreny@hawaii.edu