Growth of a thrombosed giant vertebral artery aneurysm after parent artery occlusion.

Parent artery ligation is an accepted treatment for intracranial aneurysms that are not amenable to a direct surgical approach. Parent artery ligation is one of the oldest effective surgical means of aneurysm therapy (the "Hunterian principle" (1 ]). Recently it has become possible to perform parent artery occlusion of the carotid or vertebral artery percutaneously by using detachable balloon technology [2-5]. We report a case of a patient with a vertebral artery giant aneurysm, which was treated by parent artery occlusion of the vertebral artery, resulting in thrombosis of the aneurysm. In spite of thrombosis of the aneurysm and the parent artery, the aneurysm continued to grow. This case suggests that giant aneurysm growth is not always dependent on pulsatile blood flow as a driving force, and that recurrent mural hemorrhage into the highly vascularized aneurysm wall is a more likely mechanism. Giant aneurysms can be unstable lesions even when they (and their parent arteries) are thrombosed. Continued surveillance with CT andfor MR imaging is prudent following thrombosis of giant aneurysms by parent artery occlusion.