Paratracheal air cysts are not an uncommon incidental finding in routine thoracic imaging. They characteristically occur on the right side, in the region of the thoracic outlet. Occasionally it may mimic pneumomediastinum, so-called pseudopneumomediastinum.
Paratracheal air cysts encompass a number of entities including 9:
There is overlap in the use and description of the terms paratracheal air cyst and tracheal diverticulum in the literature that they often seem to be synonyms for the same entity 9,10.
They are present in 3-4% of the population. They may be seen in children and adults with an increased female predilection 4.
Their exact cause is unclear and may be either congenital or an acquired phenomenon. The acquired form is thought to be due to prolonged increased intraluminal pressure, e.g. due to a chronic cough, COPD.
The cysts may be unilocular or multilocular and do not communicate the trachea. A direct connection with the trachea is visible on CT in ~35% of cases 10, and the term tracheal diverticulum may be used.
Paratracheal air cysts project posteriorly where the cartilage rings are deficient and usually lies to the right where there is no esophagus supporting the paratracheal tissue. They usually occur at the level of the thoracic inlet.
- chronic obstructive pulmonary disease (COPD): for acquired type 8
Typically located on the right side at the level of the thoracic inlet. Most measure 3-10 mm and are elongated in shape 5.
Treatment and prognosis
These are an incidental finding and no treatment is required. The biggest point is to not mistake them for something more sinister.
Imaging differential considerations include:
- pneumomediastinum: gas usually encircles trachea
- herniated lung
- pulmonary blebs
- Zenker diverticulum
Although usually asymptomatic, it may accumulate respiratory secretions that become infected and lead to coughing or tracheobronchitis.
- 1. 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 Am J Neuroradiol. 2008;29 (6): 1218-21. AJNR Am J Neuroradiol (full text) - doi:10.3174/ajnr.A1058 - Pubmed citation
- 2. Goo JM, Im JG, Ahn JM et-al. Right paratracheal air cysts in the thoracic inlet: clinical and radiologic significance. AJR Am J Roentgenol. 1999;173 (1): 65-70. doi:10.2214/ajr.173.1.10397101 - Pubmed citation
- 3. Tanaka H, Mori Y, Kurokawa K et-al. Paratracheal air cysts communicating with the trachea: CT findings. J Thorac Imaging. 1997;12 (1): 38-40. Pubmed citation
- 4. Cheng HM, Chang PY, Chiang KH et-al. Prevalence and characteristics of paratracheal air cysts and their association with emphysema in a general population. Eur J Radiol. 2012;81 (10): 2673-7. doi:10.1016/j.ejrad.2011.10.013 - Pubmed citation
- 6. Bae HJ, Kang EY, Yong HS et-al. Paratracheal air cysts on thoracic multidetector CT: incidence, morphological characteristics and relevance to pulmonary emphysema. Br J Radiol. 2012;86 (1021): 20120218. doi:10.1259/bjr.20120218 - Pubmed citation
- 7. Kim JS, Kim AY, Yoon Y. Paratracheal air cysts using low-dose screening chest computed tomography: clinical significance and imaging findings. Jpn J Radiol. 2011;29 (9): 644-8. doi:10.1007/s11604-011-0608-4 - Pubmed citation
- 8. Webb EM, Elicker BM, Webb WR. Using CT to diagnose nonneoplastic tracheal abnormalities: appearance of the tracheal wall. AJR Am J Roentgenol. 2000;174 (5): 1315-21. AJR Am J Roentgenol (full text) - Pubmed citation
- 9. Tanrivermis Sayit A, Elmali M, Saglam D, Celenk C. The diseases of airway-tracheal diverticulum: a review of the literature. (2016) Journal of thoracic disease. 8 (10): E1163-E1167. doi:10.21037/jtd.2016.10.92 - Pubmed
- 10. J.E. Buterbaugh, W.K. Erly. 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. (2008) American Journal of Neuroradiology. 29 (6): 1218. doi:10.3174/ajnr.A1058 - Pubmed