Clinical features of congenital cystic disease of the mediastinum. Diagnostic usefulness of computed tomography and magnetic resonance imaging

We describe 18 cases of congenital mediastinal cysts, including 4 bronchogenic cysts, 5 pericardial cysts, and 9 thymic cysts. Fifteen of the 18 patients (62.5%) were asymptomatic, and the cysts were found incidentally on a chest radiograph conducted as a part of a physical screening. In 2 of the 4 cases of bronchogenic cysts, the cystic lesions were located in the posterior mediastinum and in the cephalad recess of the azgos vein (CRAzV). In 3 of the 5 cases of pericardial cysts, the lesions were located in the right cardio-phrenic region. In the remaining 2 cases, the cysts were located in the CRAzV and in the posterior mediastinum. Seventeen patients who had histologically proven mediastinal cysts were investigated by magnetic resonance (MR) imaging. In all 3 cases of bronchogenic cysts, MR signals of the cysts were of higher intensity than those of muscle on T1-weighted images. Neither the pericardial cysts nor the thymic cysts showed high signal intensity on T1-weighted images. Macroscopically, the intracystic fluids in all of the bronchogenic cysts contained viscid mucus that probably caused high signal intensities on the T1-weighted images. MR imaging is not only useful in revealing the location of mediastinal cysts, but also in the differential diagnosis of congenital mediastinal cysts. (author)