Causes of Pneumomediastinum
Pneumomediastinum is most commonly caused by alveolar rupture with air tracking along the bronchovascular sheaths to the mediastinum, but can also result from various traumatic, iatrogenic, and pathological processes affecting the airways, lungs, or adjacent structures.
Primary Causes
Alveolar Rupture (Spontaneous Pneumomediastinum)
- Increased intrathoracic pressure events:
Trauma-Related Causes
- Blunt chest trauma 5
- Barotrauma (particularly during diving/ascent) 6
- Occurs when compressed gas expands during ascent
- Risk increases with localized airway narrowing or lung parenchymal weakness 6
Iatrogenic Causes
- Mechanical ventilation with high pressures
- Post-procedural complications:
Pathological Causes
- Esophageal perforation/rupture 5
- Tracheal or bronchial disruption 5
- Laryngeal injuries 5
- Mediastinal infections
- Hollow viscus perforation 4
Diagnostic Considerations
Clinical Presentation
- Retrosternal chest pain (65% of cases) 1
- Dyspnea (51% of cases) 1
- Subcutaneous emphysema (common finding) 3
- Hamman's sign (crunching sound synchronized with heartbeat) - present in minority of cases 3
Imaging Findings
- CT scan is the most sensitive diagnostic tool (100% detection rate) 5
- Can identify patients at high risk for aerodigestive tract injury with 100% sensitivity and 85% specificity 5
- Chest X-ray may miss pneumomediastinum (detected in only 15% of cases confirmed by CT) 5
- Radiographic signs include 4:
- Thymic sail sign
- "Ring around the artery" sign
- Tubular artery sign
- Double bronchial wall sign
- Continuous diaphragm sign
- Extrapleural sign
Management Approach
For Spontaneous Pneumomediastinum
- Conservative management is typically sufficient 1
- Observation without extensive workup is appropriate for most cases 1
- Spontaneous resolution usually occurs within 7 days 3
- Low recurrence rate after conservative management 1
For Suspected Secondary Pneumomediastinum
- CT scan should be the preferred initial screening tool 5
- Additional investigations only if CT suggests aerodigestive tract injury 5
- Surgical consultation for cases with:
- Suspected esophageal perforation
- Airway injury
- Hemodynamic instability
- Worsening symptoms
Special Considerations
Diving-Related Pneumomediastinum
- Presents with central chest discomfort, hoarseness, and dyspnea 6
- May be associated with arterial gas embolism (potentially fatal) 6
- Can occur even after shallow dives (5 meters) 6
Post-Procedural Pneumomediastinum
- Following esophageal dilatation, suspect perforation if patient develops pain, breathlessness, fever, or tachycardia 6
- Chest X-ray may show pneumomediastinum, pneumothorax, or pleural effusion, but normal appearance doesn't exclude perforation 6
Idiopathic Cases
- No precipitating event identified in approximately 41% of spontaneous pneumomediastinum cases 1
- Typically affects young adults (mean age 19-24 years) 2, 1
- Male predominance (53-72%) 2, 1
Pneumomediastinum is generally a benign condition with excellent prognosis when managed appropriately, but careful evaluation is necessary to rule out serious underlying causes requiring specific interventions.