Following the regional standard regimen, dual antiplatelet therapy (DAPT) with aspirin (100 mg/day) and prasugrel (3.75 mg/day) was initiated 2 weeks before the subsequent treatment. Under general anesthesia, bilateral distal radial artery access was achieved using an anatomical snuffbox. Two guiding catheters (RIST 7F; Medtronic) were inserted into the right and left vertebral arteries (VAs). Through the left side, a Vecta 46 (Stryker) was placed as a distal access catheter (DAC), and a Headway-27 (Terumo Neuro) was guided from the basilar artery (BA) to the left PCA. A FRED-X (3.5 mm × 23 mm; 17 mm working length; Terumo Neuro) was chosen as the FD. Through the right VA, another Vecta 46 was positioned as a DAC, and a VIA-27 (Terumo Neuro) was navigated into the aneurysm. A WEB SL (8 mm × 3 mm) was used. These devices were selected based on the precise measurements derived from 3-dimensional DSA (Fig. 1G). A FRED-X was first deployed by unsheathing the Headway-27 until it reached the neck (Fig. 1I). The deployment of the WEB through the VIA-27 was initiated using an unsheathing maneuver (Fig. 1J). The FRED-X was further deployed until it covered two-thirds of the neck. In contrast, the WEB was fully deployed by adjusting its shape through push-pull movements, thereby fixing the right PCA origin without covering the origin of the right superior cerebellar artery (SCA). After confirming that the right SCA origin was in contact with the FRED-X but not covered by the WEB, the WEB was detached, followed by the removal of VIA-27. Finally, the FRED-X was fully deployed by unsheathing the Headway-27. For the endovascular treatment procedure, see Supplementary Video 1 (captured Fig. 1K). Final DSA and cone-beam CT confirmed the optimal placement (Fig. 1L). The patient recovered well, and DAPT was continued postoperatively. Diffusion-weighted MRI on postoperative day 1 revealed no abnormalities; the patient was discharged the following day. At the 4-month follow-up, DSA revealed complete obliteration of the aneurysm with good FRED-X patency. The right SCA remained intact, whereas the right PCA was supplied via the PCoA. The angle between the BA and the left PCA was reduced by the straightening effect of FRED-X (Fig. 1M–P). DAPT was planned to be continued for 6 months, with a scheduled DSA 12 months before discontinuation.

Intrasaccular flow disruption using a WEB for bifurcation aneurysms has been established as a standard treatment for aneurysms of appropriate size and morphology for the device, supported by numerous cases and accumulated evidence [1-4]. However, a certain percentage of cases require retreatment owing to recurrence [3,5]. The need for retreatment depends on the state of the residual aneurysm cavity at the time of recurrence. While a certain degree of neck remnant is acceptable, retreatment is recommended in cases with residual space between the WEB and the aneurysm wall or bleb reappearance. Reported retreatment rates vary, typically ranging from 6% to 15% [2,4,6-9]. Despite the use of the largest available WEB in the initial treatment, progressive compression led to significant recurrence with a bleb near the neck, prompting the need for definitive short-term curative retreatment.

Adjunctive strategies for WEB treatment include simple coiling, stent-assisted coiling, multiple WEB placements [10,11], and more recently, FDs with favorable outcomes [12,13]. Retreatment options for WEB recurrence include additional coiling, stent-assisted coiling, additional WEB placement, neck clipping, and FDs [14,15]. To our knowledge, no reports have described the combined use of WEB and FD placements for recurrent aneurysms following initial WEB deployment. The advantages of this strategy include enhanced prevention of blood flow into the aneurysm, achieved through the combined effects of FD flow diversion and high metal density at the WEB base for neck coverage. High cure rates are anticipated due to the scaffolding effect, which promotes endothelialization of the neck. In this case, alternative strategies such as using coils instead of the WEB device or a neck-bridging stent instead of a FD could have been considered and might also have achieved successful treatment. However, given that this was a recurrent aneurysm, the presence of a bleb near the neck requiring early complete occlusion, and the difficulty of completely occluding this bleb with ordinary coiling or even with the WEB device, we adopted the current treatment strategy. Placing the WEB to occlude the origin of the right P1, in addition to deploying the FD from the BA to the left PCA with the expectation of achieving a subsequent straightening effect, resulted in a strong anatomical flow alteration effect [16], which likely contributed to the early obliteration of the aneurysm. However, this procedure becomes more complex because of the simultaneous manipulation of the 2 microcatheters within the parent vessel. Perioperative antiplatelet therapy necessitates prolonged DAPT as required by the FD treatment protocol.

In this case, the WEB occlusion of the right PCA was deemed acceptable based on the results of the Allcock test. However, it was critical to preserve the origin of the right SCA by ensuring that the WEB base did not cover it and to confirm that this remained unchanged after FD deployment. To achieve this, the FD was partially deployed, followed by the deployment and placement of the WEB using a semi-jail technique [17], after which FD deployment was completed. The WEB was detached only after confirming that the shape of the deployed WEB did not compromise the flow in the right SCA. If the WEB placement were inappropriate at this stage, a bailout option would have been to retrieve the WEB without detachment and proceed with coil embolization by accessing the aneurysm through the anterior circulation via the right PCoA [18].

Regarding WEB size selection, we opted for a slightly oversized device relative to the measured residual cavity, considering the use of an FD and jailing of the right PCA origin. However, the favorable outcome in this case may be partly attributable to chance. Although a bilateral approach was feasible in this case because of the adequate VA diameter on both sides, this is not universally applicable. It is essential to acknowledge that the success of this treatment was facilitated by the unique anatomical features of the aneurysm and its associated parent vessels, and it may not be replicable in all similar cases.

In conclusion, we successfully treated a recurrent basilar top aneurysm using a combined WEB and FD approach, preserving vital vessels. Though technically demanding and anatomy-dependent, this method shows promise for select cases. Early results are encouraging, but further experience and long-term follow-up are needed to confirm its effectiveness.