Right paratracheal air cysts in the thoracic inlet: Clinical and radiologic significance

OBJECTIVE. The purpose of our study was to determine the CT appearance and clinical significance of a right paratracheal air cyst at the level of the thoracic inlet. MATERIALS AND METHODS. Sixty-five consecutive patients with paratracheal ai r cysts were included in this study. The location, level, size, and shape o f the paratracheal air cysts on CT were analyzed. The spirometric data, tra cheal indexes, and CT-determined emphysema scores of these patients were co mpared with those of 60 consecutive patients in a control group. RESULTS. The air cysts were located at the right posterolateral aspect of t he trachea in 64 (98%) of 65 patients and at T1-T2 vertebral levels in 57 ( 88%) of 65 patients. The mean diameter of the right paratracheal cysts was 10 mm in the axial plane and 14 mm in the vertical plane. CT showed a commu nicating channel with the trachea in five patients. The ratio of forced exp iratory volume obtained in 1 sec to forced vital capacity, and forced expir atory flow between 25% and 75% of vital capacity in patients with paratrach eal air cysts, were significantly lower than those of the control group (p < .05). Differences in the tracheal indexes and CT-determined emphysema sco res between the study group and the control group were found to be statisti cally significant (p = .001). CONCLUSION. The most probable nature of a right paratracheal cyst in the th oracic inlet is tracheal diverticulum with a narrow stalk. The presence of a right paratracheal air cyst on CT could be a sign of obstructive lung dis ease clinically and of the presence of emphysema radiologically.