Spontaneous pneumomediastinum ( Hamman ’ s syndrome )

A previously healthy, 21-year-old female nonsmoker sought emergency room treatment complaining of recent and progressive swelling of the face, neck, and chest (Figure 1). The patient reported no pain, dyspnea, or dysphagia at admission. She reported a brief history of odynophagia in the previous week, when, during an episode of cough, she felt intense (dissecting) retrosternal pain, which subsided within a few minutes after its onset. After that episode, she had no symptoms other than the abovementioned swelling. Physical examination revealed extensive subcutaneous emphysema, which extended from the xiphoid process to the temporal muscle and involved the entire neck and face. Pulmonary percussion and auscultation revealed no abnormalities. Cardiac auscultation revealed the presence of Hamman’s sign (crackles—as was the case in our patient—or bubbling sounds, synchronous with the heartbeat). Oral endoscopy revealed no abnormalities, and the remainder of the physical examination was normal. A CT scan of the skull, neck, and chest confirmed the presence of pneumomediastinum, pneumothorax (Figure 2A), and extensive soft tissue emphysema in the cervical region (Figure 2B)— involving the face, periorbital tissues, and temporal muscles (Figure 2C)—as well as revealing the presence of pneumorrhachis (Figure 2D). From postadmission day two onward, the subcutaneous emphysema gradually improved. The patient received conservative treatment, including rest, unrestricted diet, and analgesia, if necessary. The results of routine laboratory tests, including blood workup and urinalysis, were normal. Follow-up chest X-rays revealed a sustained reduction in the abovementioned signs and symptoms. The patient remained under observation for another five days, being asymptomatic and showing nearly complete resolution of the clinical picture at discharge (Figure 1). Spontaneous pneumomediastinum, also known as Hamman’s syndrome, is defined as the presence of free air in the mediastinum, being unrelated to trauma or procedures (surgical or otherwise).(1) It is an uncommon entity,(1-6) its estimated prevalence ranging from 0.001% to 0.01%.(2) Because the course of the disease is nearly always benign, many patients do not seek medical attention, which is why spontaneous mediastinum often goes undiagnosed. In addition, the presence of trauma, surgical procedures, or mechanical ventilation rules out spontaneous pneumomediastinum, therefore reducing the prevalence of the disease. Physical exercise, labor, diabetic ketoacidosis, inhaled drug use, cough, and vomiting, among others, have been reported to trigger spontaneous pneumomediastinum.(3) The primary component of the pathophysiology of Hamman’s syndrome is alveolar rupture, which results from high intraalveolar pressure, low perivascular pressure, or both. After the initial event, air tracks into the mediastinum during the respiratory cycle, the pressure in the mediastinum decreasing in relation to that in the lung parenchyma.(4) This mechanism is known as the Macklin effect or phenomenon, having been named after Charles C. Macklin, who described it in detail in 1939.(7) In two thirds of the cases, as occurred in the case reported here, spontaneous pneumomediastinum can progress and affect the cervical region(5) and, less commonly, facial tissues. Pneumorrhachis, however, is even rarer, only a few cases having been reported in the literature. (6) It is believed that, in cases of pneumorrhachis, air from the posterior mediastinum goes through the neural foramina and into the epidural space. (6) If the passage of air into the mediastinum and the previously described anatomical planes is not enough to decrease intra-alveolar pressure, pleural rupture with pneumothorax can occur,(2) Spontaneous pneumomediastinum (Hamman’s syndrome)