Neonatal pneumothorax describes pneumothoraces occurring in neonates. It is a life-threatening condition, associated with high morbidity and mortality. The diagnosis is a challenge especially when the amount of air is small and may accumulate along the anterior or medial pleural space.
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Epidemiology
Only 0.5% of cases are symptomatic despite the high incidence. Studies show a male predilection. It is more commonly seen to occur within the first three days of life with more than 80% seen in the first 48 hours 3.
Clinical presentation
Variable from being completely asymptomatic to severe respiratory distress. Symptoms include dyspnea, cyanosis and chest pain. Physical examination may reveal decreased breath sounds and hyper-resonance to percussion on the afflicted side with contralateral tracheal deviation. When under tension, cardiac function may be compromised.
Pathology
Air dissects from alveolar spaces into interstitial spaces of lung. The eventual migration of air to the visceral pleura culminates in rupture into the pleural cavity. It may also be accompanied by pneumomediastinum, pneumopericardium, pneumoperitoneum or subcutaneous emphysema.
Etiology
Pneumothorax in neonates commonly results from mechanical ventilation for infant respiratory distress syndrom (IRDS). The alveolar atelectasis in IRDS needs to be managed with positive airway pressure to prevent hypoxia. This often results in overinflation and rupture of the alveoli (termed pulmonary interstitial emphysema). The air leaking from the ruptured alveoli can either migrate peripherally to cause pneumothorax, or centrally to cause pneumomediastinum 4.
It may also occur spontaneously (from coughing or vomiting), or secondary to birth trauma, underlying obstructive or restrictive lung disease and rupture of a congenital or acquired cyst ref.
Radiographic features
Plain radiograph
There are a few signs that are useful in the diagnosis of a small pneumothorax:
hyperlucent hemithorax sign in case of anterior pneumothorax
medial stripe sign and/or sharp mediastinum sign in case of medial pneumothorax
These signs can be appreciated in the supine position with additional views to confirm:
hyperlucent hemithorax sign is seen as unilateral or bilateral areas of increased lucency confirmed on cross-table lateral view; the air will be seen to accumulate anteriorly
medial stripe sign is seen as an area of increased lucency at the interface of the medial lung and the mediastinum which can be confirmed on lateral decubitus view; the air will be seen to rise and accumulate along the lateral chest wall
Treatment and prognosis
Small, asymptomatic pneumothoraces are left alone and kept under close observation. Larger or symptomatic ones require drainage. Acute tension may be relieved with needle aspiration; chest tube or pigtail drainage may be placed afterwards for complete evacuation.
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