Asymptomatic aneurysm of the proximal right subclavian artery: a rare ultrasound diagnosis

True aneurysms of otherwise normal subclavian arteries are uncommon periphe ral vascular anomalies. Most patients with subclavian artery aneurysms are symptomatic by presenting neurologic signs. We report a young woman who had an asymptomatic true aneurysm of the right subclavian artery assumed to be of congenital origin. This case is unique in that the aneurysm was in the extremely rare :anatomic location of the right supraclavicular fossa :betwe en the origins of the right subclavian artery and the vertebral artery. Ane urysms of the right subclavian artery may represent a potential pitfall in conventional gray-scale ultrasound of the neck particularly the supraclavic ular fossa. Differential diagnosis includes cervical cyst, pharyngo-esophag eal diverticulum, vascular anomalies, struma, enlarged lymph node, as well benign or malignant neoplasms. Color duplex ultrasound should be performed as the meth od of choice for further analysis of suspected aneurysms. In th is report the role of B-mode ultrasound and color duplex ultrasound is disc ussed in relation to digital subtraction- and MR angiography in confirmatio n of the diagnosis.