The prognosis of posterior circulation aneurysmal subarachnoid hemorrhage is poor (1, 2). For patients with acutely ruptured intracranial vertebrobasilar artery-dissecting aneurysms (ari-VBDAs), if untreated, Mizutani et al. (3) reported that approximately 70% of patients subsequently underwent rebleeding, and it most commonly occurred within the first 24 h, resulting in the deaths of approximately half of those patients. Previous studies have shown that endovascular therapy tended to have better outcomes than neurosurgical clipping in the treatment of posterior circulation aneurysms (4, 5). Deconstructive treatment and single stent-assisted or multilayer stent-assisted coiling of ari-VBDAs have been described in published studies (6, 7). However, ari-VBDAs are rare, and there are limited data on the treatment outcomes regarding the imaging results and the benefits/risks of different endovascular techniques. The safety and efficacy of different endovascular treatment techniques for ari-VBDAs remain to be further explored.

A low-profile visualized intraluminal support (LVIS) device has been demonstrated to be beneficial in assisting the coil embolization of intracranial aneurysms (8). However, due to the nature of the braided stent, the LVIS stent will expand outward along the neck when treating fusiform-dissecting aneurysms, and an uneven distribution of metal coverage along the neck may affect the flow-diverting effect (9). To avoid this shortcoming, in this study, we attempted to use LVIS-within-enterprise double-stent technique with coil embolization in the treatment of ari-VBDAs. The enterprise stent was used as an external frame to limit the expansion of the LVIS stent to increase metal coverage in the aneurysmal neck (Figure 1). The current study aimed to assess the feasibility of the LVIS-within-enterprise double-stent technique with coil embolization in the treatment of ari-VBDAs.

Despite the variety of acute treatment approaches for patients with ari-VBDAs, the prevailing view is that early intervention reduces mortality and leads to favorable clinical outcomes (2, 3). However, the technique for treating wide-necked aneurysms should be chosen carefully. The deconstruction technique for vertebrobasilar dissecting aneurysms (VBDAs) has been shown to be associated with higher occlusion rates in published studies (11, 12). Due to the pathological features of the vertebrobasilar artery and its relationship to perforated branches, the indications of the deconstruction technique are strictly limited, and it is only suitable for patients with good collateral vascularization. Reconstructive treatment including flow diversion (FD), single stent-assisted coiling, and conventional series stent-assisted coiling is the mainstream treatment for VBDAs (6, 7, 13, 14). A meta-analysis by Domingo et al. (15) found similar efficacy in the occlusion rate for posterior circulation non-saccular aneurysms treated with conventional stent-assisted coiling and FD, with the complete/near-complete occlusion rates of 84% and 83%, respectively. However, due to antiplatelet regimens, device prices, and insurance coverage, the use of FD in treating ari-VBDAs has certain limitations. In addition, a meta-analysis suggests that fusiform and dissecting aneurysms may be one of the risk factors for complications of intracranial aneurysms treatment with FD (16). The off-label use of FD for the treatment of ari-VBDAs still needs further confirmation. Conventional single stent-assisted coiling, to some degree, was associated with risks of aneurysm recurrence (7, 13).

Low-profile visualized intraluminal support is a self-expanding, retrievable, braided intracranial stent indicated for the treatment of wide-necked intracranial aneurysms with ~ 23% metal coverage, and previous studies have demonstrated favorable safety and efficacy profiles (8, 17). Tian et al. (18) compared the hemodynamic effect of the pipeline flow diverter and LVIS stent in aneurysm models and found that a compacted LVIS stent may provide a flow diversion effect comparable to that of PED. However, due to the braided design, in fusiform aneurysms, the LVIS stent will expand outward along the aneurysm neck, resulting in an uneven distribution of the stent's metal coverage along the aneurysm neck, which may affect the flow-diverting effect and aneurysm-healing process. Matsuda et al. (9) deployed an LVIS blue stent in a fusiform aneurysm model and found that there were three zones of different metal coverages along the stent, defined as the mid-zone, the transition zone, and the high-density zone. The transition zone was defined as the transitional portion of the aneurysm neck and parent artery, which had the lowest metal coverage. In addition, the outward expansion may also cause proximal or distal shortening of the stent, increasing the risk of stent malposition or migration. An enterprise stent has greater radial force but less metal coverage (~ 8%) than the LVIS stent. As a laser-cut, closed cell stent, the radial force of the enterprise stent is greater than that of the LVS stent. The enterprise stent is first deployed to play the role of “the skeleton,” which could reduce the unconstrained segment size across the aneurysm neck and limit the outward expansion of the LVIS stent. The LVIS-within-enterprise stenting could maintain the flow-diverting effect with a relatively high metal coverage distribution and promote the aneurysm healing process. Moreover, the unconstrained length of the LVIS stent ranges from 10 to 30 mm, and due to the braided design, the LVIS stent is at risk of shortening and migrating, which may be insufficient to cover aneurysms with long-segment lesions. The length of the enterprise stent ranges from 14 mm to 37 mm, and the original length can be maintained after deployment. Therefore, in some patients with lengthy lesions, the LVIS-within-enterprise stenting not only provides better flow-diverting effects but also prevents stent shortening or migrating.

As reported by Mizutani et al. (3), for patients with ari-VBDAs, 70% of the patients underwent rebleeding, and 56.7% of the rebleeding occurred within 24 h and 80% occurred within the 1st week, resulting in a mortality rate of 46.7%. To reduce the rate of rebleeding, early intervention to completely occlude the ruptured aneurysm is necessary. However, many cases of recurrent VBDAs after endovascular treatment have been reported (7, 13, 19). In their study, Kim et al. (13) found that the recurrence rate was 19.4% for patients with vertebrobasilar fusiform aneurysms, with a mean follow-up time of 9.2 months. The other study by Kim et al. (19) showed a recurrence rate of 13% for patients with ruptured or unruptured VBDAs and found that PICA involvement was associated with recurrence. In our study, we attempted to use LVIS-within-enterprise stent-assisted coiling in the treatment of patients with ari-VBDAs and demonstrated a complete occlusion rate of 93.3%. No aneurysm recurred in the available imaging follow-up data.

A retrospective study by Church et al. (20) included 84 ruptured or unruptured posterior circulation fusiform aneurysms treated with microsurgical and endovascular approaches. The authors reported that the neurological complication rate was 14%, and 67% of the complications were ischemic strokes. Peng et al. (21) noted that the procedure-related complication was 23.4% for patients with basilar trunk and vertebrobasilar junction aneurysms, including 16.9% of patients with ischemic complications. Another study reported that the overall SAEs rate and ischemic stroke rate were 15.7% and 13.7%, respectively, after the endovascular treatment of vertebrobasilar aneurysms (6). Published studies have reported that ischemic complications accounted for the majority of all complications after the endovascular treatment of posterior circulation or vertebrobasilar aneurysms. In our study, the incidences of periprocedural and overall postprocedural ischemic complications were 3.3% and 10.0%, respectively, which were similar to previous findings (6, 20, 21). Inadequate stent expansion, antiplatelet drug hyporesponse or non-response, and thrombus detachment during the stenting or coiling may be the potential causes of ischemic complications after endovascular therapy.

Another problem with the endovascular treatment of a ruptured aneurysm is rebleeding. In the ISAT trial, the rebleeding rate was 4.2% during the 1st year after endovascular treatment, and a meta-analysis of 2,121 patients conducted by Boogaarts et al. (22) revealed that a large aneurysm size is associated with aneurysmal rebleeding. In our study, one patient experienced postprocedural rebleeding (aneurysm maximum diameter: 15.6 mm). The coil embolization and deployment of relatively high metal coverage stents may lead to rapid intra-aneurysmal thrombus formations. The autolysis of the aneurysm wall associated with acute intra-aneurysmal thrombosis may be a possible cause of rebleeding (23).

There are some limitations. The present study was retrospectively designed with a relatively small sample size, and the potential bias inherent in retrospective research was inevitable. In addition, among the surviving patients, 46.2% of patients were lost to imaging follow-up, which might bias the evolution of the aneurysm occlusion. Moreover, the present study was not compared with other treatment modalities, and the differences in safety and efficacy between LVIS-within-enterprise stenting and other treatment modalities are unclear. Thus, further comparative studies with long-term follow-up are needed.

The findings in this study suggest that the LVIS-within-enterprise double-stent technique with coil embolization may be a feasible method for the treatment of ari-VBDAs, and have a good safety profile and high technical success rate. The rate of complete aneurysm occlusion during follow-up seemed to be satisfactory.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by the Institutional Review Board of The First Affiliated Hospital of Harbin Medical University. The patients/participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

QW, YM, HS, and PW contributed to the study conception and design. QW, YM, AC, SX, CW, ZJ, JQ, KY, and JS contributed to data acquisition, data interpretation, and data analysis. QW and YM drafted the manuscript. HS and PW contributed to the major revision of the manuscript. HS, PW, SX, CW, and ZJ contributed to the significant intellectual content. All authors made significant contributions to the study and manuscript preparation and critically revised the article and approved the final version of the manuscript.