The advent of an era of aneurysm coiling has substantially covered a wide spectrum of intracranial ruptured or unruptured aneurysms. The rapid development of additional devices and techniques for endovascular coiling has practically allowed treatment of more complex aneurysms that seem to have unfavorable anatomies.4)9)10)14) However, wide-neck bifurcated aneurysms cannot be favorably protected by an additional device such as a balloon or stent and a multi-catheter. Although Y-stenting or waffle cone stent-assisted coiling has been precisely developed to cover a whole range of aneurysm neck, it has an increased risk of thromboembolism or reduced completeness of occlusion.7)13) We report two consecutive cases of wide-neck bifurcated aneurysm for which a stent was horizontally deployed via catheter looping. To our knowledge, anterograde manipulation has not been demonstrated yet.

Endovascular coil embolization in wide-neck bifurcated aneurysms is still a challenge because of concerns regarding coil herniation and subsequent occlusion of the main branches due to complex geographical anatomy. Several advanced techniques with a stent, balloon, and multiple microcatheters have been well established with reasonable results.3)5)17) However, when both efferent vessels are incorporated into the wide neck of the aneurysm, the balloon can be a limited option, and Y-stenting or Waffle cone stentings may increase the risk of thromboembolic events or decrease the completeness of the coil packing.1)7)

The horizontal stenting technique has been described for wide-neck bifurcated aneurysms as able to access another route through the circle of Willis, and a single stent is perpendicularly placed on the long axis of the aneurysm, covering the whole surface of the neck.2) In most cases, the technique is indicated for basilar or internal carotid bifurcation aneurysms if they have a patent channel based on the size and tortuosity of the posterior or anterior communicating artery.2)11)12) Even if it is possible within the overall anatomy, the profile of the delivery catheter can cause technical difficulty due to the long course of navigation required. It may also induce vessel perforation or dissection during the procedure.6) Furthermore, bilateral femoral punctures have to be an option for retrograde access with an additional device. Nevertheless, small case series have demonstrated the benefits of retrograde horizontal stenting in conditions where another competent route is available at the wide-neck bifurcated aneurysms. It can cause less flow disturbance at the aneurysm neck and risk of thromboembolic complications than other multiple stents while securing the complicated aneurysm neck.2)6)11)

In the present two cases, we performed coil embolization after horizontal deployment of Enterprise and Neuroform Atlas stents by using an antegrade approach for the BABIF and MCBIF aneurysms via a catheter looping technique.4) As a retrograde route is not guaranteed, some important points have to be considered in anterograde stent deployment. First, the diameters of the efferent vessels on both sides should provide sufficient space to enable looping and maneuvering of the delivery microcatheter as noted in previous technical notes.16) The stent passes through that point by alleviating tension, completely depending on the vessel diameter. Originally, with the profile of the Enterprise stent, direct passage through the bended segment of a 0.021-in microcatheter is impossible.8) Once the distal segment of the stent is fixed to one side of the vessel, while pushing the stent, the microcatheter is looped into the contralateral side, and then the remaining portion of the stent is spanned by unsheathing the microcatheter.16) In contrast, the Neuroform Atlas stent fits through small-profile microcatheters (0.0165 in) and provides easier accessibility from its original profile than the Enterprise stent.15) Owing to its high flexibility, the stent itself can pass through the looping segment, which is the most resistant part, before deployment. Second, if the stent length is much longer than the expected range of each branch, it creates challenges for the navigation and deployment within a looping catheter. The proximal segment of the stent can be impossible to move toward the looping segment or can induce the folding of some part. The shorter length of the stent reduces friction and tension as the stent moves into the microcatheter and is beneficial for tracking the looping curve.

Even though anterograde horizontal stenting by microcatheter looping is a novel application, the indication for its use has to be precise. Owing to the technical difficulty from the course and geographical anatomy of the efferent vessels, microcatheter looping is not possible, excessive attempts may be troublesome, such as in an unexpected dissection or perforation of branching vessels. Even with looping, depending on the situation, the microcatheter may need to be deployed toward the conventional direction, for example, from one efferent branch to the main parent vessel, because of the stiffness or size of the stent. Some evidence of the usefulness of this approach might be retrospectively or prospectively obtained in large-volume studies conducted to prove its safety and feasibility in technical application in relevant anatomies.

The treatment of wide-neck bifurcated aneurysms may be technically challenging despite the use of additional devices. The antegrade horizontal deployment of a stent via catheter looping.