CASE 9783 Published on 18.03.2012

Idiopathic spontaneous pneumomediastinum


Chest imaging

Case Type

Clinical Cases


Capozzi Rodolfo G, Lucas Antonio I, Gilligan N

CEDIP; Hernandez 362.
(6450) Pehuajó;

9 years, female

Area of Interest Anatomy, Bones, Education ; Imaging Technique CT, Conventional radiography
Clinical History
A 9 year-old previously healthy female patient presented with right ear pain and odynophagia, ipsilateral parotid swelling of sudden onset with no history of trauma, coughing or straining.

On clinical examination subcutaneous emphysema was confirmed in right temporoparietal region, neck and upper chest with good air entry in both lungs.
Imaging Findings
Air in the retropharyngeal soft tissue and perilaryngeal and subcutaneous tissue was noted in the thoracic outlet. Submandibular soft tissue was enlarged. The body of the hyoid was moved forward (Fig. 1).
The chest radiograph showed interstitial air juxtahilar between the left main pulmonary artery and the mediastinal pleura and subcutaneous emphysema in the soft tissues of the neck (Fig. 2, 3).
Neck CT showed dissection of the different compartments due to the presence of interstitial air, with no evidence of rupture of organs (Fig. 4 - 7).
Chest CT revealed air dissecting supraaortic and subaortic mediastinal structures. Subcutaneous emphysema was noted in the presternal region without concomittant pneumothorax (Fig. 8, to 13).
Skull CT was normal except for presence of gas in subcutaneous tissue of the right frontotemporoparietal area without associated bone lesions (Fig. 14).
Spontaneous pneumomediastinum is characterized by the presence of air in the mediastinum in a patient without known underlying cause and is benign and self-limited. The first report was made by Hamman in 1939 [4, 6]. The incidence is unknown.
The mediastinum is connected to the submandibular space, retropharyngeal space, neck vessels, gastrointestinal tract, retroperitoneum (through periesophageal and periaortic fascial) and pelvis through the flank [5, 6]. The retropharyngeal space and prevertebral space communicate with the mediastinum neck. The prevertebral space continues down to the coccyx [7].
The pathophysiology of the mechanism consists of 3 steps: the terminal alveoli rupture, the air dissection along the peribronchovascular sheaths and the extent of interstitial emphysema in the mediastinum (Macklin effect) [6]. The alveolar rupture is a sudden increase in intraalveolar pressure, associated with cough or valsalva, exceeding the pressure in the pulmonary vasculature, releasing the air produced by interstitial emphysema, peribronchovascular sheaths dissected and interlobar septa. On the pressure gradient, the air can produce progress to pneumomediastinum or hilum to the periphery and produce pulmonary subpleural bullae and pneumothorax. The rupture of the alveoli in the pleural space can cause pneumothorax with no evidence of mediastinal emphysema. Finally, it can extend into the subcutaneous tissues of the chest wall and anterior cervical region, following the fascial planes and into the spinal canal [1].
The main symptoms are chest pain and dyspnoea [1], odynophagia [8], cough, nausea, vomiting [3] secondary to the dissection of tissues over the air or compression [9]. Retrosternal chest pain worsens with movement or breathing. Dysphagia and dysphonia are present if the air dissects retropharyngeal or perilaryngeal spaces [10].
Hamman's sign (pericardial crunch synchronous with the heart) is not pathognomonic [11].
Treatment is conservative. Pneumomediastinum evolves smoothly and resolves in 3 to 15 days without sequelae. No fatalities have been reported. In 32% of cases it may be complicated by pneumothorax [2, 3, 4, 8, 9, 11, 12].
Spontaneous pneumomediastinum is rare in children. A high index of suspicion is necessary in young patients with chest pain and signs of subcutaneous emphysema. A chest and lateral neck radiograph are initial tools for the initial diagnosis and should be supplemented by chest CT to rule out underlying lung disease or other causes of secondary pneumomediastinum and assess its extent.
Supportive therapy and clinical observation is sufficient in most cases as pneumomediastinum is self-limited (Fig. 15, 16).
Differential Diagnosis List
Idiopathic spontaneous pneumomediastinum
Secondary pneumomediastinum
Cardiac ischaemia
Mallory-Weiss syndrome
Boerhaave syndrome
Asthma in children
Respiratory infections
Final Diagnosis
Idiopathic spontaneous pneumomediastinum
Case information
DOI: 10.1594/EURORAD/CASE.9783
ISSN: 1563-4086