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Diagnosis: Pneumomediastinum with Cervical Soft Tissue Emphysema
Pneumomediastinum (pneuma is Greek for “air”) is an uncommon condition that can be spontaneous or secondary to the perforation of a gas-filled structure. Pneumomediastinum, described as free air in the mediastinum, is a benign condition when not associated with pneumothorax. (Thorax 1983;38:383; Ann Emerg Med 1992;21:1222.)
Spontaneous pneumomediastinum is an uncommon condition in children, and is often secondary to alveolar rupture into the bronchovascular sheath associated with asthma. (Pediatr Emerg Care 1996;12:98.) Less commonly it can occur from a Valsalva-type maneuver. (Eur J Pediatr 1996;155:695.) It is most common in tall, thin men for unknown reasons. (Chest 1991;100:93.) Pneumomediastinum is rarely caused by disruption of the gastrointestinal tract, upper respiratory tract, or intrathoracic tract.
Patients at risk for developing pneumomediastinum include those with underlying lung disease (COPD, cystic fibrosis), infants with acute respiratory infection (Pediatr Radiol 2007;37:1286), patients receiving positive airway ventilation (Ann Thorac Surg 1984;37:511), bleomycin treatment (Hinyokika Kiyo 2013;59:545), barotraumas (Aviat Space Environ Med 2005;76:63), a history of vomiting, GERD (Respirology 2008;13:744), strenuous exercise, coughing, inhalation of irritant gasses or recreational drugs (Respiration 2003;70:407; BMJ Case Rep 2013 Jun 7; doi:pii:bcr2013009961), foreign body aspiration (Pediatr Radiol 1989;20[1–2]:45), colonoscopy (J Am Geriatr Soc 2013;61:1433; Case Rep Emerg Med 2013;2013:583287), and recent pulmonary function testing.
Free air typically travels along the bronchovascular sheath into the hilum and mediastinum, then into the loose subcutaneous tissues of the throat and neck because the mean pulmonary parenchymal pressure is greater than the mean mediastinal pressure. Air rarely dissects into the pericardium or thorax, but can result in pericardial tamponade or tension pneumothorax, respectively. (Ann Thorac Surg 1984;37:511.)
Patients with pneumomediastinum can present with chest pain (most often pleuritic and retrosternal), dyspnea (common), neck pain or swelling, facial swelling, sore throat, and dysphagia. (Ann Emerg Med 1992;21:1222.) Less commonly patients may complain of abdominal pain and dysphonia.
Patients also may have palpable subcutaneous emphysema (typically in the neck or anterior chest wall), dyspnea, distended neck veins (if tension pneumomediastinum physiology exists), or Hamman's sign (precordial “crunching” sound synchronous with the heartbeat, often muffling typical heart sounds). (Ann Emerg Med 1992;21:1222.)
The emergency department diagnosis of suspected pneumomediastinum is made by obtaining AP and lateral chest radiography. Patients with air in the mediastinal space will have dark lucent streaks that outline the mediastinal structures, often tracking into the neck. (AJR Am J Roentgenol 1996;166:1041.) The evaluation of pneumomediastinum depends on the suspected etiology. Primary pneumomediastinum or pneumomediastinum because of a suspected benign etiology typically does not require further evaluation if no signs of tamponade or pneumothorax exist. Traumatic mechanisms where gastric or hilar disruption is suspected require further evaluation. Diagnosing tracheobronchial injury includes direct visualization with a flexible bronchoscopy. (Anaesth Intensive Care 2002;30:145.) Esophageal disruption can be evaluated using water-soluble contrast esophagography or direct visualization with esophagography.
The treatment for uncomplicated pneumomediastinum is expectant management (Ann Thorac Surg 2008;86:962) and avoiding maneuvers that increase intrathoracic pressure such as vomiting. Very rarely a limited mediastinotomy is performed to liberate a tension pneumomediastinum. (Chest 1992;102:503; J Emerg Med 2013 Aug 29. doi: 10.1016/j.jemermed.2013.04.052 [Epub ahead of print].) There is no consensus about how long to observe patients with uncomplicated pneumomediastinum. (Ann Thorac Surg 2003;75:1711.)
This patient was found to have extensive mediastinal air and subcutaneous gas greater in the soft tissues of the right nice than the left, dissecting along the carotid arteries and internal jugular veins suggesting penetrating injury in the neck or thorax. The patient was taken to the operating room, and flexible nasopharyngolaryngoscopy, direct laryngoscopy, direct esophagoscopy microtracheoscopy, bronchoscopy, and flexible upper endoscopy were performed with no identifiable source found. The patient was observed in the hospital for two days with significant improvement in the pneumomediastinum and cervical and epidural air collections. He was discharged without incident.
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