Intracranial aneurysm treatment with coil embolization is associated with relatively low complete occlusion and high recanalization rates. The investigators evaluate whether Willis covered stent implantation yields angiographic and clinical results superior to those with coil embolization.

Endovascular treatment of intracranial aneurysms with detachable coils has been widely used since the introduction of GDCs in 1991 and has been proven to be effective in preventing rebleeding after aneurysmal rupture. The clinical and angiographic results of endovascular coil occlusion of intracranial aneurysms are positive, with an initial and final overall complete occlusion rate of 35.9%-76.8% and 38.3%- 87.8%. In the mid- and long-term, however, aneurysm recanalization may occur in as many as one-third of cases.

The natural history of aneurysm recurrence after coil treatment is often benign, but bleeding from incompletely coiled aneurysms is a well-documented threat, moreover, the degree of aneurysm occlusion after treatment was strongly associated with risk of rerupture. Even if 100% occlusion of the aneurysms after the initial treatment was obtained on immediate postembolization angiography, there was still a relatively high recanalization rate (26.4%) on long-term follow-up angiography. In a recent study, we have confirmed that there was still aneurysm perfusion of the aneurysm sac in a complete occluded aneurysm no matter on initial or follow-up rotate digital angiography. In addition, some authors have demonstrated that endothelialization of the aneurysm orifice following placement of GDCs can occur; however, it appears to be the exception rather than the rule.

To overcome these disadvantages, the Willis covered stent, specially designed for intracranial vasculature, has been developed by our institution and the MicroPort Medical Company (Micro-Port, Shanghai, China). Our preliminary results demonstrated good flexibility and efficacy of the Willis covered stent in the treatment of cranial internal carotid artery aneurysms (CICA) in patients without an extremely tortuous ICA (Radiology 2009; 253:470-7), and also the covered stents have been proved to be more effective than re-coiling with regard to complete occlusion of recurrent aneurysms (J Neurol Neurosurg Psychiatry 2009;16:[Epub ahead of print]). Since 2005, we have performed a nonrandomized prospective trial of endovascular treatment CICA aneurysms with a covered stenting or coil embolization. So, we evaluate whether implantation of a primary Willis covered stent yielded angiographic and clinical results that superior to those with the currently recommended approach of coil embolization.

Inclusion Criteria:

1. Definite CICA aneurysm, either ruptured or unruptured, as demonstrated by arterial angiography;
2. Parent artery diameter of 3.0-5.0 mm;
3. Good tolerance of BOT; and
4. At least one control angiogram taken > 6 months after the initial treatment

Exclusion Criteria:

1. An extremely tortuous vessel proximal to the parent artery and/or lack of appropriate accessible routes, thereby rendering the patient unsuitable for endovascular treatment;
2. Parent artery diameter of < 3 mm or > 5.0 mm;
3. Inability of the patient to undergo general anesthesia or endovascular intervention; or
4. Expected patient survival of < 1 year because of other co-existing diseases. -