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

Abstract

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. Sixty-five consecutive patients with paratracheal air cysts were included in this study. The location, level, size, and shape of the paratracheal air cysts on CT were analyzed. The spirometric data, tracheal indexes, and CT-determined emphysema scores of these patients were compared with those of 60 consecutive patients in a control group. The air cysts were located at the right posterolateral aspect of the 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 communicating channel with the trachea in five patients. The ratio of forced expiratory volume obtained in 1 sec to forced vital capacity, and forced expiratory flow between 25% and 75% of vital capacity in patients with paratracheal air cysts, were significantly lower than those of the control group (p < .05). Differences in the tracheal indexes and CT-determined emphysema scores between the study group and the control group were found to be statistically significant (p = .001). The most probable nature of a right paratracheal cyst in the thoracic 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 disease clinically and of the presence of emphysema radiologically.