Paratracheal Air Cysts

General Considerations

• Benign incidental finding on CT (rarely seen on chest radiographs)
• 2.0% to 3.7% of the population
• Most are probably tracheal diverticulum
  • On imaging, 35% have a narrow stalk to the trachea
• Histology shows ciliated columnar epithelium

Clinical Findings

• None
• Not associated with either trauma or emphysema

Imaging Findings

• Always located on the right posterior trachea at the level of the thoracic inlet (~T2)
• Unilocular or multilocular air-filled cystic structures
• 2-20 mm in diameter on axial plane
• Frequently associated with contour abnormality of trachea
• May or may not see connection to trachea

Differential Diagnosis

• Herniated lung
  • Remains in continuity with the lung
• Emphysematous blebs
• Laryngocele
• Mounier-Kuhn Syndrome
  • Also has tracheomegaly and bronchiectasis
• Pneumomediastinum
  • Air usually encircles trachea

Treatment

• None required 

Paratracheal Air Cysts. Axial CT: There is a small pocket of air (blue and green arrows) located to the right and slightly posterolateral to the trachea (T) at the levels of C7-T2. Sagittal reconstruction: Multi located collections of air (red arrow) communicate with the posterior aspect of the trachea (T) by a thin stalk (yellow arrow).
For these same photos without the arrows, click here and here
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Buterbaugh JE, Erly WK. Paratracheal air cysts: a common finding on routine CT examinations of the cervical spine and neck that may mimic pneumomediastinum in patients with traumatic injuries. AJNR. 2008 Jun;29(6):1218-21

Goo JM, Im JG, Ahn JM, Moon WK, Chung JW, Park JH, Seo JB, Han MC. Right paratracheal air cysts in the thoracic inlet: clinical and radiologic significance. AJR. 1999 Jul;173(1):65-70