566 J ENDOVASC THER 2001;8:566–570 l CASE REPORT l Overlapping Stents for Treatment of a Dissecting Carotid Artery Aneurysm Goetz Benndorf, MD1; Adriana Campi, MD1; Gerd Helge Schneider, MD2; Ernst Wellnhofer, MD3; and Andreas Unterberg, MD2 Departments of 1Radiology, 2Neurosurgery, and 3Cardiology, Charité, Humboldt University, Berlin, Germany l l Purpose: To report the increased efficacy of oversized, overlapping stents to treat an internal carotid artery (ICA) dissecting aneurysm. Case Report: A 55-year-old woman presented with reduced consciousness, aphasia, and right-sided hemiplegia owing to an infarction of the left middle cerebral artery territory documented by computed tomography. Digital subtraction angiography disclosed an extracranial dissection of the left ICA with a pseudoaneurysm. Two self-expanding Wallstents were placed, bridging the dissected segment and overlapping at the level of the aneurysm neck. Immediate arteriography showed remarkably reduced filling of the pseudoaneurysm. Serial arteriograms performed 6 days and 9 and 20 months after stenting documented the disappearance of the pseudoaneurysm without appreciable intimal hyperplasia of the vessel wall. Conclusions: Reducing stent porosity by overlapping the devices causes significant hemodynamic changes inside the aneurysm sac, accelerating intra-aneurysmal thrombosis. J Endovasc Ther 2001;8:566–570 Key words: internal carotid artery, pseudoaneurysm, cerebral infarction, Wallstent, aneurysm sac thrombosis l l Wide-necked arterial aneurysms of the extracranial carotid artery are difficult to treat surgically if located close to the base of the skull. Coil embolization may not be successful, particularly in large aneurysms. The application of metallic stents has shown increasing promise for endovascular treatment of dissecting aneurysms in the extracranial and, more recently, the intracranial carotid territories.1–6 Depending on local hemodynamics, complete aneurysm occlusion by stent placement is Address for correspondence and reprints: Goetz Benndorf, MD, Neuroangiography/Neurointervention, Department of Radiology, Charité, HU Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. Fax: 49-30-4506-0933; E-mail: g.benndorf@charite.de usually achieved within a few months,3,4 but this requires repeated angiography and extended anticoagulation. We present a patient with a dissecting carotid aneurysm that was successfully occluded within a few days by placing 2 oversized, overlapping, self-expanding stents. CASE REPORT A 55-year-old woman presented with reduced consciousness, aphasia and right-sided hemiplegia (21 on the National Institutes of Health Stroke Scale). Computed tomography revealed an infarction of the left middle cerebral artery territory. Digital subtraction angiogra- Q 2001 by the INTERNATIONAL SOCIETY OF ENDOVASCULAR SPECIALISTS J ENDOVASC THER 2001;8:566–570 OVERLAPPING STENTS IN CAROTID DISSECTION BENNDORF ET AL. 567 Figure 1 l (A) Anteroposterior (AP) view of the left internal carotid showing a 20-mm widenecked pseudoaneurysm and a 5-cm segment of irregular luminal narrowing of the cervical vessel. (B) In another AP arteriogram taken 6 days after deployment of 2 overlapping Wallstents, the pseudoaneurysm has been successfully occluded. The diameter of the carotid lumen has also been normalized to improve flow to the cerebral circulation. (C) Overlapping interstices of the double stents reduce the porosity across the aneurysm neck (arrowheads). phy (Fig. 1A) showed dissection of the left extracranial internal carotid artery (ICA) with a moderately stenosed segment and a 10 3 20 mm pseudoaneurysm at the C1 level. The pseudoaneurysm did not radiographically resolve over a 3-month observation period, so carotid stenting was performed to improve cerebral blood flow to the left hemisphere and forestall further thromboembolic events. Anticoagulant treatment was started 4 days prior to stenting using clopidogrel (150 mg/d) and aspirin (325 mg bid). A 9-F guiding catheter was placed into the left common carotid artery, and heparin (5000 units) was administered as an intra-arterial bolus through the sheath. Two self-expanding 8-mm-diameter Wallstents (Boston Scientific, Natick, MA, USA) were deployed so that one 40-mm-long stent bridged the entire dissected segment, while a 30-mm-long stent was placed within the first to span the aneurysm orifice. The completion arteriogram (Fig. 1B,C) showed a patent ICA with remodeling of the dissected vessel wall; only minimal opacification of the aneurysm was evident in the late venous phase. Clopidogrel was continued for 3 weeks and aspirin indefinitely after the procedure. Arteriography 6 days after stenting showed complete disappearance of the aneurysm and 568 OVERLAPPING STENTS IN CAROTID DISSECTION BENNDORF ET AL. J ENDOVASC THER 2001;8:566–570 Figure 2 l (A) Follow-up arteriogram (AP view) 20 months poststenting documents no significant intimal hyperplasia. The maximum endothelial reaction (double arrows) is seen outside of the area covered by the double stents, which begins about 20 mm distal to the bifurcation (single arrow). 3D reconstructions after rotational angiography (view from below) demonstrate a slightly increased thickening at the level of the bifurcation (B, axial slice at lower line in A), which is covered by a single stent, compared to a more distal segment covered by double stents (C, axial slice at upper line in A). preservation of the carotid artery. The followup arteriograms at 9 and 20 months (Fig. 2A) demonstrated a fully patent carotid lumen without significant intimal hyperplasia, which was confirmed by three-dimensional (3D) reconstructions (Fig. 2B,C) of rotational angiographic images. The patient partially recovered from her stroke (functional Barthel Index improved from 5 to 30 [maximum 100]), and she suffered from no further ischemic attacks. DISCUSSION Most pseudoaneurysms associated with spontaneous dissection or trauma typically follow a benign course7; however, it is rare that they regress radiographically with anticoagulant therapy; Guillon et al.7 found that 65% of dissecting carotid aneurysms remained unchanged in their study, 30% decreased in size, and only 5% resolved completely. Less fre- J ENDOVASC THER 2001;8:566–570 OVERLAPPING STENTS IN CAROTID DISSECTION BENNDORF ET AL. 569 quently, dissecting pseudoaneurysms can cause significant clinical complications, such as thromboembolic events that require more aggressive treatment. Because these lesions are often located close to the skull base, surgical access may be complicated or impossible. Hence, various endovascular techniques are increasingly employed to manage cervical carotid aneurysms.1,3,4 Similar to techniques employed in the intracranial circulation, electrolytically detachable coils may be used for selective extracranial aneurysm occlusion, as Lempert et al.8 demonstrated in their 11 successfully treated patients. However, endosaccular coil packing of pseudoaneurysms lacking a true arterial wall always carries the risk of rupturing the false sac, so this technique is not used in our institution. Furthermore, most pseudoaneurysms arising from dissection are wide-necked, and coils may migrate into the parent vessel, thus limiting complete aneurysm occlusion. As an increasingly popular alternative to embolotherapy, stents have proven safe and effective for exclusion of pseudoaneurysms while preserving the parent vessel.1,3,5 One disadvantage of stents, however, is that complete occlusion of the aneurysm is rarely achieved initially; it may take 3 to 6 months1,3 or longer1–3 to see total thrombosis. Liu et al.2 recently reported on long-term outcome after stent placement in 7 patients, including 4 with dissection-induced pseudoaneurysms. Only 2 cases had complete occlusion of the aneurysm at the time of the procedure; 1 underwent additional coil packing and another showed resolution after 18 months. To enhance the speed of occlusion, ancillary deployment of coils before or after stenting has been advocated for extracranial4 as well as for intracranial9 lesions. Most recently, covered stents have also been applied for immediate exclusion of these lesions.5 While stent-grafts are theoretically the ideal implants for covering arterial aneurysms, they are still evolving and have several disadvantages,10 such as higher thrombogenicity,9 that can increase the risk of premature stent occlusion. Cejna et al.,11 in an experimental study comparing various stent-grafts to bare stents, found that covered stents induce more inflammatory vessel wall reaction with neointimal hyperplasia. They observed a marked reaction, with 50% luminal stenosis caused by a polyester-covered endoprosthesis. We are unaware of other reports of using overlapping stents (double stenting) for complete exclusion of wide-neck aneurysms in the carotid arteries, but it appears to be a relatively simple technique to more effectively change intra-aneurysmal flow to promote thrombosis. The effect may be further enhanced by oversizing the stents (JJ Vitek, personal communication), which reduces the overall flow into the aneurysm, as well as the pressure by increasing turbulence in the area of the struts or wireforms. Aenis et al.12 demonstrated in a sidewall aneurysm model that flow is significantly diminished inside the stented aneurysm with less undulation in the parent vessel. Pressure zones at the distal neck and the dome decreased post stenting, and shear stress rates at the distal neck were elevated but more confined and unidirectional compared to the nonstented model. The influence of stent porosity on local hemodynamics between the aneurysm and the parent vessel has been shown experimentally.13 Yu and Zhao14 were able to demonstrate that dampening of the intra-aneurysmal flow by stents is effective if the ratio of the mesh area to the total surface of the stent is sufficiently small, regardless of the size of the aneurysm. The flow movement inside the aneurysm sac can be reduced to #5% of the bulk mean flow velocity, inducing intra-aneurysmal thrombus formation. Our case supports these experimental results, showing that overlapping stents reduce porosity, thus significantly impeding intra-aneurysmal blood flow. Blood stasis within the aneurysm likely accelerates intrasaccular thrombus formation. Double stenting undoubtedly increases the foreign body material in the arterial wall, yet restenting and double stents are common practice in cardiology and seem to be rather safe.15 Twenty months after stenting, the arteriogram in our patient demonstrated only a mild, nonstenotic area of luminal narrowing, similar to the intimal hyperplasia commonly observed after carotid stenting. However, the maximum endothelial growth occurred in a vessel segment covered 570 OVERLAPPING STENTS IN CAROTID DISSECTION BENNDORF ET AL. J ENDOVASC THER 2001;8:566–570 by a single stent, not in the area of stent overlap, suggesting that the inner stent does not create significant additional injury to the vessel wall. Rotational angiographic imaging was able to demonstrate the varying thickening of the wall at the sites of the single and double stents. Although further studies are needed, this new imaging technique seems to be helpful in better appreciating intraluminal morphology pre- and poststenting. Stents with low porosity are not available at the moment, and other adjunctive methods of single stenting suggested for the occlusion of pseudoaneurysms have some limitations. Additional injection of glue into the aneurysm may be unsafe and risky, whereas coil packing of the sac can be difficult and is rather expensive.6 Double stenting may be a simple and effective alternative treatment for symptomatic dissecting aneurysms. It should be evaluated and compared to other invasive treatments currently explored in interventional neuroradiology. New imaging techniques, including 3D reconstruction, intravascular ultrasound, or angioscopy, may become helpful investigative tools for guiding therapy. rotid artery: combined endovascular treatment with coils and stents. AJNR Am J Neuroradiol. 1997;18:1261–1264. 5. Marotta TR, Buller C, Taylor D, et al. Autologous vein-covered stent repair of a cervical internal carotid artery pseudoaneurysm: technical case report. Neurosurgery. 1998;42:408– 413. 6. Roth TC, Chaloupka JC, Putman CM, et al. Percutaneous direct-puncture acrylic embolization of a pseudoaneurysm after failed carotid stenting for the treatment of acute carotid blowout. AJNR Am J Neuroradiol. 1998;19:912–916. 7. Guillon B, Brunereau L, Biousse V, et al. Longterm follow-up of aneurysms developed during extracranial internal carotid artery dissection. Neurology. 1999;53:117–122. 8. 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