Spontaneous pneumomediastinum with a classical radiological sign.

A 38-year-old male, with past history of pulmonary tuberculosis, was referred to us with worsening of dyspnea for 4 days. Dyspnea was initially relieved by bronchodilators, but for the past 2 days, there was no effect of the medications given. He denied any history of trauma, drug abuse, or vigorous exercise. His past history was significant for regular, adequate antituberculosis treatment taken 10 years back. Clinical examination revealed a hyperresonant percussion note, reduced intensity of breath sounds on left side, and presence of palpable crepitations over the neck and chest wall suggestive of surgical emphysema. The patient was in respiratory distress with tachypnea (34/min) and hypoxia (89%) on room air. An X-ray of the chest was done urgently [Figure 1].

Figure 1

Can you appreciate a radiological sign?

What are the radiological abnormalities?

What is your diagnosis?

Briefly discuss the condition with radiological signs.

ANSWERS

Answer 1: An incomplete film showing extensive surgical emphysema, air in the left pleural cavity and paracardiac region, collapse left lung, a linear hyper-translucent opacity running between the lower border of heart and diaphragm [Figure 2], along with high-density nodular lesions in lung fields.

Figure 2

Let's have a closer look at the radiograph

Answer 2: Spontaneous pneumothorax on the left side, pneumomediastinum with “continuous diaphragm sign” and healed pulmonary tuberculosis.

Answer 3: The presence of air within the connective tissue planes of the mediastinum is called “pneumomediastinum or mediastinal emphysema.” The most common cause is traumatic rupture of alveoli with the dissection of air along the bronchovascular interstitium and its forced entry into the mediastinal connective tissue by respiratory excursions. Less commonly, it may be caused by tracheobronchial or esophageal rupture, penetrating neck injuries, or mediastinitis caused by gas-forming bacterias.[1] Spontaneous pneumomediastinum is not a common clinical disorder although observed in a variety of situations, i.e., intense exercise, scuba diving, cocaine abuse, or any cause of increased intrapleural pressure such as straining, positive pressure ventilation, sneezing, coughing, vomiting, etc.[23] There have been many clinical conditions describing the occurrence of pneumomediastinum, i.e., asthma, tuberculosis, pneumonia, silicosis, bronchogenic carcinoma, etc.[45]

Often presenting with chest pain, an acute onset of dyspnea, and swelling over neck, chest wall, and face, pneumomediastinum can be diagnosed easily on chest X-ray films. The radiological features of pneumomediastinum include the visualization of subcutaneous emphysema, free mediastinal air as hyperlucent lines enhancing mediastinal viscera and outlining the lateral heart borders along with superior mediastinal widening. Other signs include continuous diaphragm sign, continuous left hemidiaphragm sign, ring-aroundpulmonary-artery sign (air surrounding the extrapericardial segment of the right main pulmonary artery and appearing as a lucent ring around the right pulmonary artery), thymic/spinnaker sail sign (outlining of the thymus due to large pneumomediastinum elevating the thymic lobes), V sign (confluence of innominate veins outlined in a frontal view), Naclerio's V sign (air outlining the lateral border of the descending aorta and extending laterally between the parietal pleura and medial left hemidiaphragm), pneumoprecardium, air in the pulmonary ligament, tubular artery sign, double bronchial wall sign, and extrapleural sign. A lateral chest X-ray is also helpful in detecting increased retrosternal air, and increases the detection rate of pneumomediastinum. Vertical translucent air streaks around the aorta and pulmonary artery also are diagnostic of pneumomediastinum.[67]

“Continuous diaphragm sign” was first described by Levin.[8] It is the visualization of the continuous border of diaphragm against the contrast of the heart shadow. Normally obscured by the heart border, the presence of air delineates the central diaphragmatic border clearly. This is best seen in frontal radiographs taken during expiration. This sign is also useful in trauma patients, as it is seen in supine films also in contrast to the other signs.[9]

Spontaneous pneumomediastinum has a benign course, resolving on its own. The management of this condition is usually supportive with reassurance, observation, treatment of underlying condition, and oxygen therapy. Coexistent pneumothorax should be treated on its own merits. However, occasional deaths from splinting of great vessels and trachea by the mediastinal emphysema have also been reported, demanding careful vigilance on this condition.[210]