Fig. 4

a) Catheter venography of the right internal jugular vein showing the significant reduction of the cross sectional area either at the upper level, corresponding to the previous site of compression, or at the lower level, corresponding to a rigid valve apparatus; b-c). Delayed clearance of the contrast dye; d) Optimal morphological result after balloon angioplasty (PTA), functionally corresponding to a prompt drainage of the contrast dye