Bilateral subclavian artery aneurysm associated with idiopathic cystic medial necrosis.

Although cystic medial necrosis, either idiopathic or associated with Marfan's syndrome, usually becomes manifest as an ascending aortic aneurysm, aortic insufficiency, aortic dissection, or a combination of these disorders, a rare case of bilateral subclavian artery aneurysm secondary to idiopathic cystic medial necrosis has occurred. Subclavian artery aneurysms most commonly represent poststenotic dilatation from anterior scalene or cervical rib compression, occasionally are associated with generalized arteriosclerotic peripheral vascular disease, and rarely are secondary to syphilitic or mycotic infections. Subclavian artery aneurysms have a major risk of rupture, embolus, or thrombosis, and therefore should be repaired. A reverse saphenous vein or prosthetic bypass graft from the carotid to the axillary artery provides adequate flow to the upper extremity. The aneurysm should be completely excised if possible, since reexpansion through small collaterals or through insufficient closure by ligation can occur and compress the brachial plexus after successful bypass. The clinical presentation, angiographic findings, and operative repair of a subclavian artery aneurysm secondary to cystic medial necrosis are described.