Pneumomediastinum is defined as the presence of air or other gas in the mediastinum. This can be categorized as spontaneous or traumatic. Traumatic pneumomediastinum is caused by blunt or penetrating trauma to the chest or iatrogenic injury. Mediastinal air commonly originates from pneumothoraces (4,8). Pneumomediastinum in the absence of pneumothorax is frequently omitted in the differential diagnosis of retrosternal chest pain. It is an uncommon condition predominantly seen in young men. It typically presents with chest pain, dyspnea, and neck pain (11). Diagnosis requires a high index of suspicion, because evidence of its occurrence may not present on examination or chest X-ray. This is usually a benign, self-limited condition, which responds well to conservative management, with recurrence being rare (10–12). However, there is a small subset of patients who require a more extensive work-up for more serious injuries, including aerodigestive injuries. Here, is a case of a healthy young man who developed a pneumomediastinum, without pneumothorax, after blunt trauma to the thorax during a soccer match with several features suspicious for more serious injuries.
A 21-yr-old male soccer player sustained a midback injury during a soccer match. Midway through the first half, he was struck in the left midback by an opposing player's knee while lunging for a headed ball. He initially noted midback pain, but did not have any associated dyspnea, chest pain, or other cardiopulmonary symptoms. Sideline assessment was unremarkable, and after several minutes, he was able to return to play without any difficulty. Approximately 12 h after the initial injury, the athlete developed retrosternal chest pain, and pain in the anterior neck, associated with deep inspiration and swallowing, as well as shortness of breath. At that time, he was brought to the emergency department for further evaluation.
On presentation to the emergency department he was noted to be in mild distress secondary to retrosternal chest pain and neck pain. Vital signs were stable, with O2 saturation 98% to 100% on room air. Examination of the neck revealed no tenderness, crepitus, or JVD. Chest examination showed mild tenderness with palpation along the inferior aspect of the posterolateral left chest wall without crepitus. No ecchymosis or other skin changes were noted. Cardiovascular examination was unremarkable. Pulmonary examination showed the lungs to be clear to auscultation bilaterally with good air movement; no wheezes, rales, or rhonchi noted.
A chest X-ray showed outlining of the right cardiomediastinal silhouette and subcutaneous emphysema over the neck suggestive of pneumomediastinum without associated pneumothorax (Fig. 1). A computed tomography (CT) scan of the neck and chest revealed extensive soft tissue emphysema extending throughout the mediastinum into the neck and retropharyngeal tissues (Fig. 2), as well as throughout the mediastinum (Fig. 3).
Given the presence of pneumomediastinum without associated pneumothorax after blunt trauma to the chest, as well as odynophagia, there was concern of aerodigestive injury. A gastrograffin swallow evaluation was performed which did not show any extravasation of contrast.
The patient was monitored in the emergency department for several hours. He remained hemodynamically stable and was eventually discharged home from the emergency department with specific instructions to return if symptoms worsened. After 72 h, the patient’s symptoms improved, and after a 7-d gradual return to play, he was able to return to play without any further sequelae.
Pneumomediastinum was first described by Laennec in 1819 as a consequence of traumatic injury. It is a condition in which free air is found within the mediastinum. Historically, the incidence of pneumomediastinum has been described as 4% to 10% following severe blunt thoracic trauma (4). It occurs predominately in young men with peak prevalence between the second and fourth decades of life. This presumably reflects involvement in activities that increase the risk for developing pneumomediastinum.
Several proposed mechanisms for pneumomediastinum in athletes include forceful coughing, forceful straining during exercise, or other activities associated with a valsalva maneuver, forced expiration against a closed glottis (i.e., during tackling), or blunt trauma to the cervical spine, chest, or thoracic spine (9,10). A vast majority of mediastinal air originates from pneumothoraces, as high as 72% in some studies (4,8).
Pneumomediastinum occurs as air leaks through small alveolar ruptures to the surrounding bronchovascular sheath. Because the mean pressure in the mediastinum is always less than the pressure in the pulmonary parenchyma, the free air tends to move centripetally along the vascular sheaths, perhaps facilitated by the pumping action of breathing. The air dissects to the hilum and spreads into the mediastinum or through the loose mediastinal fascia to the subcutaneous tissues of the thorax, upper limbs, and neck (12,13).
Most common symptoms described are chest pain (50% to 90%), dyspnea, and neck pain. Less common features include odynophagia, dysphagia, dysphonia, back pain, and cough. Physical examination is unremarkable in up to 40% of uncomplicated pneumomediastinum (2,9,10,12). Physical examination findings include subcutaneous emphysema, typically detected in the neck and precordial areas; a crunching, rasping sound, synchronous with the heartbeat, heard over the precordium, and in many occasions associated with muffling of heart sounds (Hamman’s sign) (2,5,11,12). In most cases, the movement of air into the subcutaneous tissues prevents the buildup of pressure in the mediastinum. Rarely, pressure accumulates in the mediastinal cavity, causing compression of adjacent intrathoracic structures (tension pneumomediastinum) (6).
Pneumomediastinum is a radiographic diagnosis. The features of pneumomediastinum on X-ray are generated by leaked air itself and enhancement of margins of mediastinal structures by the air. Radiographic findings on plain films include: 1) air outlining mediastinal structures, usually seen most clearly just above the heart on the left side; 2) retrosternal air on lateral films; 3) subcutaneous emphysema (1,5).
X-ray has a low sensitivity (25% to 31%) (2–4) with CT scan being a more sensitive imaging modality (sensitivity 69%–100%) (2–4,8). CT scan appears necessary to establish a correct diagnosis when chest X-ray findings are inconclusive, but there remains a high clinical suspicion for pneumomediastinum (10). They also are useful to demonstrate the extent of the pneumomediastinum, as well as other associated injuries which may require further work-up. The athlete presented in this case did have a chest X-ray showing outlining of the right cardiomediastinal silhouette and subcutaneous emphysema over the neck, suggestive of pneumomediastinum, without associated pneumothorax. A CT scan was ordered in this case to better assess degree of mediastinal air, as well as other possible injuries, which may require further work-up.
Some advocate an aggressive approach to diagnostic work-up for those patients presenting with pneumomediastinum, with some recommending mandatory evaluation of all patients with bronchoscopy and esophageal imaging to exclude major aerodigestive injury. However, the presence of pneumomediastinum as a proxy for aerodigestive injury remains controversial. Recent studies have shown aerodigestive injuries to be rare (1.6%–7%) with the vast majority of patients with pneumomediastinum having no aerodigestive injury (2,4,8). Overtriage may lead to an increased incidence of unnecessary invasive work-up and lead to an increased cost burden due to prolonged hospitalization (4). However, when dealing with a patient with pneumomediastinum located in proximity of aerodigestive structures when no pneumothorax can explain mediastinal air coupled with odynophagia and hoarseness, an aerodigestive work-up is required.
Athletes presenting with pneumomediastinum of unclear etiology, without associated pneumothorax, or in the setting of blunt cervical, chest or thoracic trauma, there should be a higher degree of suspicion for an aerodigestive injury, which may serve as an indicator for a highly selective work-up (i.e., bronchoscopy; gastrograffin swallow study) (4,8). This was the case with our patient who was found to have pneumomediastinum without an associated pneumothorax, as well as odynophagia. Given this atypical presentation, it was assumed there was a more serious areodigestive injury and therefore a more selective work-up was performed, including gastrograffin swallow study to assess for esophageal perforation.
Return to play guidelines for pneumomediastinum following blunt trauma are not well established. Many advocate that young, healthy patients found to have free air in the mediastinum require only observation with conservative treatment consisting of administration of oxygen, bed rest, and analgesics, with serial chest X-rays to monitor resolution of air (4,9–11). Symptoms associated with pneumomediastinum tend to resolve, without sequelae, within 3 to 15 days with complete reabsorption of mediastinal air occurring within 3 to 8 days (10,12). Some recommend patients may return to full activity once their chest radiographs have returned to normal, they exhibit no symptoms, and they have regained their stamina (7). After recovery, restriction of exercise and avoidance of possible predisposing factors is unnecessary (10). Our patient’s symptoms improved after 72 h. Serial chest x-ray were not performed to ensure resolution of mediastinal air, however, clinically patient was stable. After a 7-d gradual return to play, he was able to return to competitive soccer without any further sequelae and without restrictions.
Pneumomediastinum should be considered in athletes who present with complaint of chest pain, shortness of breath, and neck pain after blunt trauma to the chest. This tends to be a benign, self-limited condition which responds well to conservative treatment. Understanding the benign nature of this condition may obviate the need for unnecessary diagnostic and therapeutic interventions. However, a highly selective work-up may be necessary to rule out other more serious conditions, including aerodigestive injuries.
The authors declare no conflict of interest and do not have any financial disclosures.
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