Effect of obstructed mediastinal venous return on dynamic brain blood flow studies: Case report.

Three patients are described who had unusual isotope brain flow studies in which the injected isotope refluxed into the internal jugular vein, entered the transverse dural sinuses, and returned proximally to a variable extent through the contralateral internal jugular vein. Mediastinal flow studies revealed obstructed pathways of venous return in the upper mediastinum. One patient had lymphoma, another had had a pneumonectomy, and the third had no demonstrable disease process to explain the flow pattern. The internal jugular-cerebral system apparently permits reversal of flow in the presence of unilateral obstruction proximal to the internal jugular vein.