Right subclavian artery aneurysm yin yang sign on CT

Abstract

True subclavian artery aneurysm (SAA) is a rare type of peripheral artery aneurysm. Thoracic outlet syndrome and atherosclerosis are the most common etiological factors [1]. Halsted [2] explained the poststenotic dilatation and the aneurysm development to be a result of turbulent flow near the narrowing and low blood pressure distal to the stenosis. The famous concept of “yin-yang” which represents a balance and equilibrium between good and evil is a classical Doppler sign of pseudoaneurysms. Mural thrombus in the SAA may also cause this appearance on contrast-enhanced CT (CECT) examination. In this report a case of true SAA due to a cervical rib and yin-yang appearance on CECT is presented.