Introduction
Recently, endovascular treatment of intracranial aneurysms has substantially improved. However, wide-necked intracranial aneurysms have been particularly difficult to treat using a simple coil embolization technique. Various techniques, such as two-catheters, balloon-assisted, stent- assisted or balloon-in-stent have facilitated the treatment of wide-necked intracranial aneurysms, as previously demonstrated in the literature.1)2)12)15)18)19)23)24) Despite these advancements, the treatment of the wide-necked aneurysms at the arterial bifurcation is still challenging.
There have been some reports on Y-stent-assisted coil embolization of wide-necked bifurcation aneurysms, but most of the data from the literature are either case reviews or technical reports. To determine both the feasibility and the safety of the Y-stent-assisted coil embolization, we reported a series of eight consecutive patients with wide-necked bifurcation aneurysms treated with this method.
Materials and Methods
We retrospectively reviewed the medical records of the patients using the Y-stent-assisted coil embolization from August 2007 to October 2010. The study was performed on 8 consecutive patients with 8 intracranial aneurysms. Three out of eight aneurysms were located at the anterior communicating artery (ACOM), three at the top of basilar artery (BA), one at the middle cerebral artery (MCA) bifurcation and one at the pericallosal artery. The size of aneurysms ranged from 3.6mm to 28.2mm (mean 8.7mm, median 6.8mm, neck size from 3 to 7mm). Four patients were female and the age of all patients ranged from 52 to 73 years (mean 60 years). Among the eight patients, there were six unruptured aneurysms and the remaining two patients presented with subarachnoid hemorrhage. One patient presented with recurrence of an aneurysm previously managed with a balloon-assisted coil embolization. All aneurysms had wide-neck (i.e. neck size more than 4mm or unfavorable dome to neck ratio) and were located at the arterial bifurcation. Among the six cases with unruptured aneurysms, five were incidentally found and one was by with transient ischemic attack (TIA). The patients’ characteristics are summarized in Table 1.
Four cases were treated with the Y-stent-assisted coil embolization after failure of other neck remodeling techniques (e.g. two-catheters, balloon-assisted, stent-assisted, or balloon-in-stent); the remaining four cases were treated with Y-stent-assisted coil embolization as the first choice (i.e. the main branches were incorporated into the aneurysm sac). In all the unruptured aneurysm cases, the patients were pre-medicated for 5 days with dual antiplatelet therapy, consisting of 75mg clopidogrel and 100mg aspirin. The right femoral artery was accessed with a 6-French, 80cm-lengthed Shuttle sheath (Cook, Bloomington, IN USA). Under general anesthesia, we placed a 6-French guiding catheter (Envoy, Cordis, Miami Lakes, Fla.) in the distal segment of the internal carotid artery (ICA) for the anterior circulation aneurysm and in the distal V2 segment for the BA top aneurysm. After gaining access to the femoral artery, a bolus of 3000 IU of heparin was administered intravenously at the beginning of the procedure in cases of unruptured aneurysm. However, in cases of ruptured aneurysm, heparin was administered after a microcatheter replacement. An additional 1000 IU bolus of heparin was administered every hour to maintain an activated clotting time of longer than 250 seconds throughout the procedure.
In the management of the ACOM aneurysms, a 6F guide catheter was first advanced through the ipsilateral petrous ICA under constant road map fluoroscopy. The standard over-the-wire technique was used to advance the microcatheter to the A1-A2 junction. A 300cm-length microwire was passed through the mircocatheter putting the distal tip of the microwire at distal A3 and the microcatheter was withdrawn. A pair of Neuroform stents (Boston Scientific, Natick, Massachusetts, USA) were then prepared. The first stent advanced into the more acute angled A2 segment to facilitate deployment of the second stent. The microwire was totally withdrawn and 200cm-length microwire was used to select the contralateral A2 segment though the stent struts. After selection of the contralateral A2 with the micocatheter, we changed the microwire to the 300cm-length microwire with the same maneuver. The second stent was advanced over the wire from the A1 into the A2 in a fashion that partially overlapped the A1 segment. The so-called “Y” configuration was thus established around the ACOM and both the microwire and the catheter were then carefully retrieved back into ACOM. Subsequently, the wire was drawn into the aneurysm and the catheter was advanced over the wire. Coil embolization was attempted. Aneurysms arising from the BA and the MCA bifurcation were managed in a similar fashion.
In the four cases where the other remodeling techniques failed, such as the two-catheters technique, several coils were initially packed into the aneurysm sac using two microcatheters. When a coil protruded into the parent artery, the coil was totally withdrawn and the microcatheter was slightly withdrawn a few millimeters. Using the microwire, we selected the distal artery which was more compromised with the protruded coil. Similar to the maneuver described above, the first stent advanced into the selected artery and was deployed. The second stent was then navigated to the other artery. After second stent deployment, we finished the coil embolization using a jailed microcatheter.
Immediately after the procedure, all patients underwent non-enhanced brain computed tomography (CT) for evaluation of possible complications from hemorrhagic and 2,850IU of low-molecular heparin (Fraxiparin, Glaxo Smith Kline, Marly-le-Roi Cedex, France) was administered subcutaneously two or three times a day for 24~72 hours. Oral antiplatelet medication continued for more than 6 months. Follow-up angiograms were usually performed at 6 months postembolization, and after the follow-up angiogram, we decided to stop antiplatelet medication.
Results
The Y-stent-assisted coil embolization was successfully performed in all 8 cases. The Immediate angiographic results were complete occlusion in 7 cases and remnant neck in one case. Six patients (75%) underwent angiographic follow-up, ranging from 2 to 15 months (mean 9 months). The follow-up angiographic results confirmed a stable embolized state of all aneurysms without in-stent stenosis or thrombosis except in one case. Angiographic and follow-up results are summarized in Table 1.
There was one acute cerebral infarction complication due to distal coil migration and one delayed cerebral infarction from in-stent thrombosis after 2 months. Acute thromboembolism (TE) during the procedure occurred in four patients, but all cases were resolved by intra-arterial abciximab injection. One patient suffered an acute cerebral infarction in the left anterior cerebral artery (ACA) territory due to coil migration to the distal A3. We attempted to remove the coil with a snare but failed. Delayed angiography revealed the flow obstruction at the distal A3 with insufficient leptomeningeal collateral flow but the patient was returned to his previous state of health after 6 months. No patient died from procedure-related complications. As a result, treatment-related periprocedural permanent morbidity and mortality were 12.5% and 0%, respectively.
Illustrative cases
Case 1
A 60-year-old male patient visited the hospital due to sudden decreased mental status. The CT angiography showed SAH owing to rupture of the left MCA bifurcation giant aneurysm. The patient’s Fisher grade was IV and the Hunt-Hess grade was V. Digital subtraction angiography (DSA) confirmed the presence of the 28mm-sized ruptured aneurysm located in the left MCA bifurcation. Due to the wide unfavorable neck size, the Y-stent-assisted coil embolization was selected as the primary treatment modality. However, the aneurysm’s size was huge and therefore there was the limitation of increasing the packing density of the coiled aneurysm using the Y-stent assisted technique. So, we decided to use two microcatheters and the Y-stent-assisted technique. For this procedure, both femoral arteries were accessed with a 6-French, 80cm-lengthed Shuttle sheath (Cook, Bloomington, IN USA). We placed two 6-French guiding catheters (Envoy, Cordis, Miami Lakes, Fla.) in the distal segment of the ICA and midcervical ICA. Successful embolization was accomplished without significant complication (Fig. 1).

Case 2
A 73-year-old female patient presented with a history of headache. The brain MRI and MRA revealed an unruptured BA top aneurysm. DSA confirmed the presence of the aneurysm and revealed that both PCAs were incorporated into the aneurysm sac. Stent-assisted coil embolization with the “Y” configuration was elected as primary treatment. Complete occlusion of the aneurysm was achieved and the patient remained neurologically intact and stable until the day of discharge. Two months later, she developed sudden onset of visual field defects. The magnetic resonance imaging (MRI) revealed acute cerebral infarction in the right PCA territory. The DSA confirmed the right PCA occlusion which usually means acute in-stent thrombosis. There was no evidence of recanalization of the embolized aneurysm. Simultaneously, chemical thrombolysis was performed and complete recanalization was achieved (Fig.2). The modified Rankin Scale (mRS) score of the patient at discharge was one, with mild visual field defect.
Discussion
Since the introduction of coil embolization in 1991, the endovascular treatments of intracranial aneurysms have substantially improved and have become the alternative modality in the treatment of intracranial aneurysm. The International Subarachnoid Aneurysm Trial (ISAT) had a pivotal role in changing the treatment strategy for ruptured intracranial aneurysms, from clipping to coiling.14) Nevertheless, the treatment of wide-necked intracranial aneurysms still remains a therapeutic challenge.
The established methods for remodeling wide-necked intracranial aneurysms are the stent-assisted (jailing catheter or stent-first) technique, the balloon-remodeling technique and the balloon-in-stent technique. These techniques have several advantages for coiling of the wide-necked aneurysms and they have been a successful alternative to the traditional coiling method. Unfortunately, they have several disadvantages such as difficulty of sac selection through the stent struts and higher rates of thromboembolism (TE). Therefore, the wide-necked aneurysms at the arterial bifurcation still have been regarded as one of the major contraindications for coiling.
Some authors have proposed novel stent-assisted coiling for the management of aneurysms located at arterial bifurcations. One of them was the use of a single stent placed perpendicularly to the BA axis in a fashion that spans from the right to the left P1 segments.5)8)21) Kelly at el. described the single stent placement across the circle of Willis via the PCOM and ACOM to treat aneurysms of the basilar apex and ACOM.8) Cross et al. also provided a case report where this technique was used in the management of a basilar apex aneurysm.5) According to Cross, this technique serves as an advantage in coil placement at arterial bifurcations. However, horizontal stent deployment requires the navigation of the PCOM through the ICA, a factor that may limit its application. Horowitz et al. reported six cases using a “waffle cone” shaped deployment of the stent at the wide-necked BA top aneurysms.7) This technique involves the deployment of a single Neuroform stent placed in the basilar artery. The distal component of the stent is allowed to fan out as it is extruded into the bifurcation at the neck of the aneurysm and following placement of the coils distal to the midline stent. The “Waffle cone” shaped stent deployment is a unique technique but has some limitations when applied to the small-sized aneurysms or an aneurysm at ACOM. The sole stenting technique could also promote thrombosis formation and aneurysm obliteration. However, the sole stent technique has proven inadequate because of high failure rates for occlusion.10) Zenteno et al.24) demonstrated the use of the stent-only therapy in 15 aneurysms at various locations, but only one case showed immediate total occlusion.
There have been several reports about the “Y” configuration stent-assisted coil embolization. Sani and Lopez suggested a technical case report wherein this configuration was applied for the wide-necked aneurysm at the middle cerebral artery.17) Perez-Arjona and Fessler indicated the treatment of an unruptured BA apex aneurysm which incorporated both P1 branches with the Y-stent-assisted technique.16) The open cell design of the stent allows both the passage and the safe deployment of a second stent through the interstices of the first stent, without compromising the flow through the bifurcation of the parent vessel. Hemodynamic assessment has shown that the “Y” configuration was advantageous with respect to reduction in the strength of the flow vortices and of the peak flow velocity.4) Multiple stent placement has an additive effect on reducing the wall-shear stress and an advantage unique to the “Y” configuration.9) This may reduce the chances of both coil compaction and aneurysm growth for the wide neck aneurysm with preserving both parent and distal arteries. In our series, among 6 angiography follow-up patients, there was no case of either recanalization or regrowth of the embolized aneurysm. But longer term follow-up periods and further experience will be required to define the stability of the procedure. Concerns regarding increased thrombogenicity, especially in the SAH patient, has been raised previously where double or cross stenting could occlude the parent vessel or the perforators.3)6)11)20)22) These thromboembolic events (TE) are due to hyperactive platelets. Intravascular stent deployment disrupts the functional endothelium and may result in inflammation followed by neointimal proliferation. In our cases, acute TE occurred in 4 patients (three in unruptured aneurysms and one in SAH patient), but all cases were resolved by intra-arterial abciximab injection after achieving sufficient coil packing density without neurologic deficits. There are some proposed reasons for the high incidence of acute TE in Y-stent assisted technique compared with other neck remodeling technique. First, the size of the stented-vessel is an important predisposing factor of acute TE. In pericallosal artery aneurysms, the stented-vessel size was too small, so the risk of acute TE was high. Procedure time is a second predisposing factor for acute TE. Y-stent assisted technique is a complex procedure and needs more time to complete.
Despite of high TE, there are some advantages of Y-stent assisted coil embolization. Coiling of wide-neck bifurcation aneurysms may result in recanalization secondary to the hemodynamics of the parent artery and to the high pressure pulsatile flow directly at the coil mass. The placement of two stents in Y-configuration may alter the flow pattern at the aneurysm’s neck, which will redirect the flow toward the bifurcation arteries to potentially reduce the likelihood of recanalization. Sometimes, it is impossible to embolize wide-necked bifurcation aneurysms, especially if both bifurcation vessels are incorporated into the aneurysms with usual neck remodeling techniques such as two catheters, balloon assisted, single-stent assisted, or balloon-in-stent. But the Y-stent assisted technique could facilitate the coil embolization of such complex aneurysms.
This report demonstrates the feasibility of the double stents in a “Y” configuration technique to facilitate coil embolization of wide-necked bifurcation aneurysms. However, studies on larger patient series are needed to further evaluate the effectiveness of this treatment in the short postoperative course, as well as for long-term outcomes.
Conclusion
Successful coil embolization of wide-necked bifurcation aneurysms were achieved by using the Y-stent-assisted technique in 8 consecutive cases. The proposed Y-stent- assisted coil embolization is a feasible treatment option for reconstruction of these complex aneurysms. But, the relatively high incidence of thromboembolism could restrict this novel technique and it is important that this method be performed in patients with no contraindications for anticoagulation or antiplatelet medication. Further studies in larger patient series and with a longer follow up period will elucidate both the efficacy and the longevity of this treatment.
REFERENCES
1)Akiba Y, Murayama Y, Vinuela F, Lefkowitz MA, Duckwiler GR, Gobin YP. Balloon-assisted Guglielmi detachable coiling of wide-necked aneurysms: Part I-experimental evaluation. Neurosurgery 45:519-30, 1999
2)Benndorf G, Campi A, Schneider GH, Wellnhofer E, Unterberg A. Overlapping stents for treatment of a dissecting carotid artery aneurysm. J Endovasc Ther 8:566-70, 2001
3)Broadbent LP, Moran CJ, Cross DT 3rd, Derdeyn CP. Management of neuroform stent dislodgement and misplacement. AJNR Am J Neuroradiol 24:1819-22, 2003
4)Canton G, Levy DI, Lasheras JC. Hemodynamic changes due to stent placement in bifurcating intracranial aneurysms. J Neurosurg 103:146-55, 2005
5)Cross DT 3rd, Moran CJ, Derdeyn CP, Mazumdar A, Rivet D, Chicoine MM. Neuroform stent deployment for treatment of a basilar tip aneurysm via a posterior communicating artery route. AJNR Am J Neuroradiol 26:2578-81, 2005
6)Fiorella D, Albuquerque FC, Han P, McDougall CG. Preliminary experience using the Neuroform stent for the treatment of cerebral aneurysms. Neurosurgery 54:6-17, 2004
7)Horowitz M, Levy E, Sauvageau E, Genevro J, Guterman LR, Hanel R et al. Intra/extra-aneurysmal stent placement for management of complex and wide-necked-bifurcation aneurysms: eight cases using the waffle cone technique. Neurosurgery 58:ONS-258-62, 2006
8)Kelly ME, Turner R, Gonugunta V, Woo HH, Rasmussen PA, Masaryk TJ et al. Stent reconstruction of wide-necked aneurysms across the circle of Willis. Neurosurgery 61:249-54, 2007
9)Kim M, Levy EI, Meng H, Hopkins LN. Quantification of hemodynamic changes induced by virtual placement of multiple stents across a wide-necked basilar trunk aneurysm. Neurosurgery 61:1305-12, 2007
10)Lanzino G, Wakhloo AK, Fessler RD, Hartney ML, Guterman LR, Hopkins LN. Efficacy and current limitations of intravascular stents for intracranial internal carotid, vertebral, and basilar artery aneurysms. J Neurosurg 91:538-46, 1999
11)Lee YJ, Kim DJ, Suh SH, Lee SK, Kim J, Kim DI. Stent-assisted coil embolization of intracranial wide-necked aneurysms. Neuroradiology 47:680-9, 2005
12)Lownie SP, Pelz DM, Fox AJ. Endovascular therapy of a large vertebral artery aneurysm using stent and coils. Can J Neurol Sci 27:162-5, 2000
13)Lozen A, Manjila S, Rhiew R, Fessler R. Y-stent-assisted coil embolization for the management of unruptured cerebral aneurysms: report of six cases. Acta Neurochir (Wien) 151:1663-72, 2009
14)Molyneux A, Kerr R, Stratton I, Sandercock P, Clarke M, Shrimpton J et al. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial. Lancet 360:1267-74, 2002
15)Moret J, Cognard C, Weill A, Castaings L, Rey A. The "Remodelling Technique" in the Treatment of Wide Neck Intracranial Aneurysms. Angiographic Results and Clinical Follow-up in 56 Cases. Interv Neuroradiol 3:21-35, 1997
16)Perez-Arjona E, Fessler RD. Basilar artery to bilateral posterior cerebral artery 'Y stenting' for endovascular reconstruction of wide-necked basilar apex aneurysms: report of three cases. Neurol Res 26:276-81, 2004
17)Sani S, Lopes DK. Treatment of a middle cerebral artery bifurcation aneurysm using a double neuroform stent "Y" configuration and coil embolization: technical case report. Neurosurgery 57:E209, 2005
18)Shapiro M, Babb J, Becske T, Nelson PK. Safety and efficacy of adjunctive balloon remodeling during endovascular treatment of intracranial aneurysms: a literature review. AJNR Am J Neuroradiol 29:1777-81, 2008
19)Sluzewski M, van Rooij WJ, Beute GN, Nijssen PC. Balloon-assisted coil embolization of intracranial aneurysms: incidence, complications, and angiography results. J Neurosurg 105:396-9, 2006
20)Vanninen R, Manninen H, Ronkainen A. Broad-based intracranial aneurysms: thrombosis induced by stent placement. AJNR Am J Neuroradiol 24:263-6, 2003
21)Wanke I, Gizewski E, Forsting M. Horizontal stent placement plus coiling in a broad-based basilar-tip aneurysm : an alternative to the Y-stent technique. Neuroradiology 48:817-20, 2006
22)Yahia AM, Gordon V, Whapham J, Malek A, Steel J, Fessler RD. Complications of Neuroform stent in endovascular treatment of intracranial aneurysms. Neurocrit Care 8:19-30, 2008
23)Youn SO, Lee JI, Ko JK, Lee TH, Choi CH. Endovascular Treatment of Wide-Necked Intracranial Aneurysms Using Balloon- Assisted Technique with HyperForm Balloon. J Korean Neurosurg Soc 48:207-12, 2010
24)Zenteno M, Modenesi Freitas JM, Aburto-Murrieta Y, Koppe G, Machado E, Lee A. Balloon-expandable stenting with and without coiling for wide-neck and complex aneurysms. Surg Neurol 66:603-10, 2006