Commentary to Letter

690

Ultrasound in Medicine and Biology

Volume 34, Number 4, 2008

COMMENTARY TO LETTER I thank Dr. A-Ching Chao and her coworkers for their comments on our study. I agree that the functional and pathophysiological significance of the valve of the left brachiocephalic vein is not sufficiently studied. The cited anatomical study by Anderhuber (1984) suggests little significance, as valves are only found in a minority of these veins, are mainly unicuspid and mostly insufficient. However, functional studies on the competency of these structures are lacking. The issue of a potential barrier to retrograde flow in the brachiocephalic vein further underlines that the appearance of contrast agent caudad to the jugular valve has to be taken into consideration as a criterion of valid insufficiency testing. The note on venous collaterals is important. However, as long as air contrast ultrasound venography (ACUV) is performed properly, venous collaterals do not interfere with insufficiency testing. Once the contrast agent appears caudad to the

valve and the Valsalva maneuver is performed, transmission of the contrast agent through the insufficient valve can be directly monitored by B-mode ultrasound. Direct monitoring rules out an overestimation of internal jugular valve insufficiency. I agree that the study of abnormal venous flow in the jugular vein and its branches is an important additional tool to investigate diseases related to cerebral venous outflow obstruction. MAX NEDELMANN, MD Justus Liebig University Giessen Germany

REFERENCES Anderhuber F. Venous valves in the large branches of superior vena cava. Acta Ant (Basel) 1984;119(3):184 –192.

doi:10.1016/j.ultrasmedbio.2007.10.013