Y-Configuration Stent Placement (Crossing and Kissing) for Endovascular Treatment of Wide-Neck Cerebral Aneurysms Located at 4 Different Bifurcation Sites

Planned and Unplanned Y-Stent Placement

In general, when wide-neck bifurcation aneurysms simultaneously involve 2 branch vessels, the planned-Y stent strategy will be selected. Furthermore, the relatively good posterior circulation access facilitates the success of the Y-stent technique. Therefore, planned Y-stent strategies were performed for most posterior circulation aneurysms in this series. When bifurcation aneurysms mainly involve 1 of the branch vessels, a single stent-assisted coiling is first attempted. However, herniation of coil loops, even local thrombus formation (case 2, Fig 1) may affect the other branch vessel, which requires a salvaging Y-stent placement. In this series, most anterior circulation bifurcation aneurysms were treated with the unplanned Y-stent strategy. This was because we preferred to try single stent-assisted coiling for these aneurysms, considering the tortuous vessel access. Generally, a single stent provided us the protection of 2 branches of wide-neck bifurcation aneurysms. Occasionally, the protrusion of a coil loop or coil mass¹⁹ might affect the other branch blood flow, resulting in the salvaging Y-stent implantation.

Crossing and Kissing Y-Configuration Stent Placement

Generally, the crossing-Y stent placement, which means deploying a second stent through the interstices of the first stent, is the traditional and most commonly used Y-stent technique. However, the crossing Y-stent technique is technically challenging, sometimes impossible for some large complex bifurcation aneurysms with unfavorable anatomic configurations, including sharp angles and an extremely wide neck. According to the angle between the distal limbs and parent trunk vessel, the most common intracranial bifurcation vessels are composed of 3 types of anatomic configurations, approximately the following: 1) T-configuration(Figs 5 and 6C), with an angle between the limbs and the trunk vessel approximately 90°; 2) Y-configuration(Fig 6A, -B), with an angle between the limbs and the trunk vessel >90°; 3) arrow(↑)-configuration(Fig 6D), with an angle between the limbs and the trunk vessel <90°. Of these anatomic configurations, the Y-configuration is technically favorable for catheterization. The T-configuration can be catheterized but with relative difficulties, and the arrow(↑)-configuration is technically the most challenging. For the arrow-configuration vessels in case 10 (Fig 4B), the catheterization of the distal branches was technically difficult. Once catheterization is successful for 1 branch, catheterizing the other branch across the interstices of the first stent is more troublesome. Moreover, the delivery and deployment of stents across the sharp angles formed by parent vessels are also very troublesome.

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Fig 5.

A crossing-Y stent for a BA apex aneurysm. A, T-configuration. B and C, After coil basketing, the first Enterprise stent was deployed, followed by the deployment of a second Enterprise stent through the interstices of the first Enterprise stent. D and E, Continuous coiling until a satisfactory embolization for the angle between stents is achieved. E and F, Comparison of postprocedural and 6-month follow-up angiograms.

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Fig 6.

Sketch of the geometries of bifurcation anatomy and 2 necks. A, D₁D₂ and E₁E₂ represent 2 necks (E₁E₂ > D₁D₂). B−D, Y-configuration, T-configuration, and arrow-configuration with approximately 2 equal aneurysm necks.

Bifurcation aneurysms have 2 necks (Fig 6) on each branch, and width is also crucial for the selection of the crossing or kissing Y-stent technique. For the crossing-Y stent technique, we usually first catheterize the branch with a relatively narrow aneurysm neck and deploy the first stent, which means that the first stent is relatively stable with a lower risk of herniation into the aneurysm sac, while catheterizing the contralateral branch through its interstices. However, some large bifurcation aneurysms, such as in case 10 (Fig 4), have 2 extremely wide necks on each branch. No matter which branch vessel was first implanted with a stent, the risk of stent protrusion into aneurysm sac was unavoidable when performing the crossing-Y technique. Consequently, in these 2 situations, and especially for cases with both sharp angles and extremely wide necks, the kissing-Y stent implantation, with 2 stents placed parallel to both distal branches down to the parent artery trunk, is preferred. Moreover, stent deployment after partial coiling is advocated for the kissing-Y stent implantation, which may provide sufficient support for the stent and increase its stability, and is favored by our experience.

In 2004, the kissing-stent technique was attempted for a BA apex aneurysm, resulting in permanent implantation of the microguidewires,³ which was not a successful kissing-stent technique. In our current series, we reported 2 cases of BA apex aneurysms reconstructed by using the kissing-Y stent technique, which are actually the first successful cases ever reported (Fig 4), to our knowledge. However, there were 2 issues of concern for us after the kissing-Y stent implantation. The first was whether these 2 stents could open well within the BA trunk. A DynaCT (Siemens, Erlangen, Germany) image showed us an excellent patency of the 2 stents (Fig 4I). The second was whether the kissing-Y stent implantation was accompanied by an increased risk of thromboembolic events due to the disturbance of regional blood flow. Although we found that the kissing-Y stent technique was safe on the basis of 2 cases of satisfactory follow-up results (1 case with a 24-months follow-up [case 10]), this technique still needs further investigation to determine its effectiveness.

Stent Selection

Since the initial report of the Y-configuration stent implantation, the recommended stent, especially the first stent, has been the Neuroform thanks to its open-cell design, which may facilitate the navigation of the second stent. However, we encountered significant difficulty in the first 2 cases (cases 3 and 4) while delivering the second stent through the interstices of the first Neuroform stent, as we previously reported.¹⁹ During the same period, we had performed 4 unplanned Y-stent techniques without any difficulty, for which the first and second choices were both Enterprise stents (cases 2 and 5–7). These experiences indicate that the use of the Enterprise stent may ease the catheterization, delivery, and deployment of the Y-configuration stent implantation. Although with the second stent there was a possibility of narrowing, especially in vessels with a small diameter, postprocedural angiograms and clinical follow-ups demonstrated the patency of 2 branch vessels and uneventful outcomes. Also, in a published study, there has been confirmation that the implantation of the Enterprise stent can potentially reduce intra-aneurysmal hemodynamic activities with the increasing likelihood of inducing aneurysm thrombotic occlusion.²⁰ For these reasons, the Enterprise stent is preferred for the Y-stent technique in our institution. In this series, a total of 7 bifurcation aneurysms were successfully reconstructed by using the crossing-Y stent technique with double Enterprise stents, with excellent angiographic and clinical follow-up results. In addition, the Enterprise is particularly advocated for the kissing-Y stent technique because these aneurysms have unfavorable anatomic configurations. For the catheterization, delivery, and deployment of stents, these unfavorable anatomic configurations demand high stent navigability and conformability. Hence, it is reasonable for Enterprise to be selected for the kissing-Y stent technique, as demonstrated by cases 10 and 11.

Efficacy and Safety of the Y-Stent Technique

On angiograms at a mean of 9.9 months, 9 (81.8%) aneurysms were completely occluded; 1 with a residual neck remained stable, and 1 was recanalized and subsequently retreated, achieving a complete occlusion. These excellent results demonstrated the efficacy and durability of the Y-stent technique for intracranial bifurcation aneurysms, which coincided with the findings in recently published literature.^21,22 In this series, the success rate of the techniques associated with the crossing-Y or kissing-Y stent was 100%. Although a thrombus event (1/11) resulting from a coil loop protrusion was encountered in case 2 (Fig 1), a salvaging Y-stent was used, achieving the patency of double branches.

Limitations

In this series, there are some limitations, such as the retrospective design, patient selection bias, limited cases in a single institution, and short follow-up time.