Abstract
Objective: The Woven EndoBridge (WEB), an intrasaccular device, is a new alternative to coils for the endovascular treatment of wide-neck bifurcation aneurysms. Selection of the correct size of the device is of utmost importance for successful treatment outcomes. We present a case of an unruptured cerebellar artery aneurysm that was successfully treated with WEB implantation, guided by a 3D silicone model for preoperative evaluation.
Case Presentation: A 67-year-old woman with no family history of cerebral aneurysms was diagnosed with an unruptured basilar-superior cerebellar artery (BA-SCA) aneurysm. The patient’s aneurysm was wide-necked with a dome of 8.1 mm, a neck of 6.5 mm, a height of 6.9 mm, and a volume of 287 mm3. In the preoperative simulation with 3D printed models, the WEB 9 × 4 mm device successfully preserved the SCA. Therefore, it was selected for treatment. Although the aneurysm had an angle of nearly 90° to the BA artery, the preoperative evaluation made it easy to guide the microcatheter and place the WEB device. The postoperative course was favorable and no new neurological symptoms were noted. Cerebral angiography performed 6 months after the procedure confirmed complete occlusion of the aneurysm.
Conclusion: Preoperative simulation with 3D printed models can help to plan device size selection and implantation position, thereby predicting intraoperative microcatheter behavior in advance.
Introduction
The Woven EndoBridge (WEB), an intrasaccular device, has been introduced as a new alternative to coils for the endovascular treatment of wide-neck bifurcation aneurysms (WNBAs). Studies comparing WEB implantation with conventional coil embolization or coil embolization with stent assistance are non-inferior, with some reporting that WEB is a safe and effective option with reduced complication rates.1–4) Although the use of this technique is expected to increase in the future, the choice of size for WEB implantation is critical for a successful outcome. Intraoperative WEB replacement due to inappropriate implantation and incorrect size selection is considered undesirable due to the risk of rupture, inadequate occlusion, and financial loss.
Recently, the effectiveness of preoperative simulation has been recognized across various surgical fields, and increasingly in the area of endovascular treatment of the brain. In particular, preoperative simulation with 3D printed models can help to plan device size selection and implantation position, as well as predict intraoperative microcatheter behavior in advance.5)
We present a case of an unruptured basilar-superior cerebellar artery (BA-SCA) aneurysm that was successfully treated with WEB implantation, guided by a 3D silicone model used for preoperative evaluation, to determine the optimal device.
Case Presentation
A 67-year-old woman with no family history of cerebral aneurysm was found to have an unruptured BA-SCA aneurysm during a close examination of a left thalamic hemorrhage that developed following a right incomplete hemiplegia. Endovascular treatment was planned 3 months after the onset of cerebral hemorrhage. Her right hemiplegia improved with rehabilitation. No neurological abnormalities were noted on admission, and her blood tests were normal. She had a history of hypertension and angina pectoris and was prescribed prasgurel hydrochloride, azilsartan, doxazosin mesylate, nifedipine, and nicorandil. A CT scan of the head revealed a subacute left thalamic hemorrhage. DSA revealed a WNBA with a dome diameter of 8.1 mm, neck diameter of 6.5 mm, and height of 6.9 mm (Fig. 1A–1C). As the neck is >4 mm and the WNBA has a dome-to-neck ratio of 1.3 (<2), we decided to perform the WEB implantation. She had been taking prasugrel for the treatment of angina pectoris, which was discontinued after the onset of the hemorrhage, and dual antiplatelet therapy with aspirin and clopidogrel was started 2 weeks before surgery.
3D modeling and simulation
Angiography: Azurion Clarity IQ (PHILIPS Japan, Tokyo, Japan).
Software: Automatically calculated using the volume measurement tool in the Interventional Workshop.
The patient’s 3D DSA data were converted to stereolithography data on Synapse Vincent. (Fujifilm, Tokyo, Japan) A 3D printer (Da Vinci Pro; XYZ Printing, Taiwan, China) was utilized to create an acrylonitrile butadiene styrene (ABS) non-A model of a non-hollow cerebral aneurysm. Moreover, a model of a cerebral aneurysm served as the internal mold. The 3D model was created by evenly applying and curing silicone around the mold and dissolving the ABS in acetone. Preoperative simulations were performed using an angiography system. A Y-connector was fixed to the central side of the 3D model. A 6-Fr guide sheath, a 5-Fr intermediate catheter, and a heat-gun-shaped VIA27 microcatheter (Terumo Neuro, Aliso Viejo, CA, USA) were inserted into the Y-connector to simulate the placement of the WEB device.
The patient’s aneurysm had a mean dome diameter of 8.3 mm and a volume of 287 mm3. The size of the recommended devices was either WEB 9 × 5 mm (318 mm3) or WEB 9 × 4 mm (254 mm3). In the preoperative simulation, both of these devices were implanted and the correct size fit was confirmed. The WEB 9 × 5 mm device could not preserve the SCA owing to its large size. However, the WEB 9 × 4 mm device successfully preserved the SCA. Therefore, the WEB 9 × 4 mm device was selected for treatment (Fig. 2A–2D).
Intraoperative findings
A right femoral artery puncture was performed under general anesthesia. A 6-Fr ASAHI FUBUKI guiding sheath (ASAHI INTECC, Aichi, Japan) and a 5-Fr JB-2 catheter (Medikit, Tokyo, Japan) coaxial system were combined with a 0.035-inch Radifocus guide wire 220 cm (Terumo, Tokyo, Japan). However, placement in the right vertebral artery was challenging due to significant bending and tortuosity. Therefore, a 5-Fr SOFIA SELECT intermediate catheter (Terumo Neuro, Tokyo, Japan) was employed as the inner catheter and guided into the right vertebral artery (V4). Angiography revealed that the aneurysm was located at the bifurcation of the BA and left superior cerebellar arteries. Additionally, the aneurysm was identified to be wide-necked, with the left SCA branching off below the neck of the aneurysm. The volume of the aneurysm was 287 mm3. Given that appropriate implantation was achieved by using a VIA27 with a 5-mm tip shaped at 90° in the preoperative simulation, the VIA27 microcatheter shaped the same way by the heat gun was delivered into the aneurysm, in combination with the Syncro SELECT soft (Stryker, Kalamazoo, MI, USA). The WEB 9 × 4 mm device was deployed from the VIA27 microcatheter. Once the WEB device was fully deployed, cone-beam CT demonstrated that the SCA was spared. Therefore, we decided to detach the WEB. The treatment was terminated because immediate post-angiography revealed that the SCA and posterior cerebellar artery (PCA) were spared and stagnation of blood flow within the aneurysm was observed (Fig. 3A–3C). Although the aneurysm, in this case, had an angle of nearly 90° to the BA artery, the preoperative study made guiding the VIA27 microcatheter and placing the WEB device easy. Following a preoperative study comparing the 9 × 4 mm and the 9 × 5 mm devices, we selected the former for treatment. The size allowed for good SCA-sparing implantation.
Postoperative course
The postoperative course was favorable and no new neurological symptoms were noted. We confirmed correct implantation of the WEB device, SCA preservation, and no embolic stroke complications on follow-up imaging (magnetic resonance imaging, magnetic resonance angiography, and computed tomography angiography). The patient was in good general condition and discharged on the 5th postoperative day. Dual antiplatelet therapy was reduced to clopidogrel only and continued for 1 postoperative month. Cerebral angiography performed 6 months after the procedure confirmed complete occlusion of the aneurysm (Fig. 3D–3F).
Discussion
The WEB device is used for WNBAs located in the anterior and posterior circulation and can be used for both ruptured and unruptured aneurysms. This device is a permanent nitinol (nickel–titanium) self-expanding mesh ball implant. Additionally, the device is available in a total of 38 size variations, with outer diameters ranging from 4.0 to 11.0 mm and heights from 2.6 to 9.6 mm available in our country. Selection of the correct size of a WEB device based on cerebral angiographic images is of utmost importance for successful treatment outcomes. According to the manufacturer’s instructions, the device must be selected by adding 1 mm to the average width and subtracting 1 mm from the average height of the aneurysm.6,7) Previous reports indicate that additional maneuvers (balloon adjustment of the device, additional stenting, and additional coiling because of the residual sac due to the undersized WEB) were necessary in approximately 27% of cases8); therefore, selecting the optimal device size for WEB may prove challenging.
Cortese et al. demonstrated that a width oversizing strategy for the WEB device was an independent predictor of aneurysm angiographic occlusion.9) Undersizing can result in poor occlusion of the aneurysm, whereas too much oversizing can cause device protrusion into the parent artery and thromboembolic complications. However, a slight width oversizing is recommended for improved outcomes.6) Selecting the appropriate oversize is essential, considering the necessary adjustments in height and volume. Preoperative simulation can aid in the selection of an appropriate size for treatment by allowing visualization of the effect of the implanted WEB device on the parent vessel and branches of the aneurysm. Previous studies have reported that aneurysm volumes are highly correlated with WEB volumes, while auto-segmentation volumes display significant differences relative to conventional height-by-width measurements. Additionally, volumetric measurements of aneurysm size are a useful adjuvant approach that assists in appropriate size selection of the WEB device.10) While this method selects an approximate volume, it has a 21% failure rate. In the present case, for example, the 9 × 5-mm (318 cm3) device is a better approximation; however, in practice, it is too large and unlikely to be successful. Therefore, both volume and height-by-width measurements were used as references for size selection in the present case.
Additionally, virtual simulation is used in clinical practice. A recent study showed that wall apposition, maximum compression, and the Spruce index (a uniformity index that quantifies variations in the radial dimensions of the WEB device from the topmost to the bottommost slice) computed by the Sim&Size medical device software (Sim&Cure, Montpellier, France) predicted the likelihood of aneurysm occlusion at follow-up after WEB treatment.11)
If a selected WEB proves to be unsuitable for the aneurysm and, therefore, cannot be implanted, modifying the size of the device becomes necessary. In such cases, it is preferable to avoid exchanging the WEB as much as possible due to the following reasons: 1) intraoperative risk (the microcatheter enters the aneurysm and causes thromboembolic complications), 2) cost, and 3) prolonged operating time.
There is a previous report that jump-up of the device is a risk for vessel perforation.12) Also, thromboembolic complications may be caused by clot formation in the guiding catheter, on the coil meshes, or in parent vessels due to induced vasospasm or malposition of coils.13) Several reports have also suggested that explainable embolic sources are air embolisms, atheroma dislodged during catheterization, thrombus formation from the device used over the course of the procedure, and hydrophilic coating from catheters and wires.14,15) Therefore, we consider that increased intraoperative manipulation also increases the potential for vascular perforation due to device jump-up and the risk of thromboembolic complications in WEB implantation.
In addition, preoperative simulation allowed us to study the shape of the microcatheter. WEB device delivery is the most straightforward in large aneurysms without significant angulation between the proximal parent artery and the long axis of the aneurysm. The difficulty of both aneurysm catheterization and WEB device deployment increases as this angle becomes significantly acute.2) If the simulation demonstrates that the VIA microcatheter (Terumo Neuro) is uncontrolled, the treatment strategy can be changed preoperatively to coil embolization or stent-assisted coil embolization. In this case, the angle between the aneurysm and BA artery was approximately 90°. However, preoperative studies have demonstrated that suitable shaping of the VIA27 microcatheter enables smooth guidance into the aneurysm and precise placement of the WEB.
Additionally, simulation offers training to the surgeon and allows the assistant to operate the actual device in addition to the surgeon. This enables the entire team to gain a comprehensive understanding of the treatment process.
However, we believe that it is necessary to carefully assess the accuracy of size selection of the 3D model compared to the size of the actual aneurysm. In this regard, we believe that future studies with more cases are necessary to determine whether the 3D model is better suited to malformed aneurysms or larger or smaller aneurysms. In the present case, there was no significant difference in measurement accuracy between the 3D model and the actual aneurysm, both in terms of aneurysm size and volume (Fig. 4).
Additionally, there are drawbacks to creating silicone models, including the cost of installing a 3D printer (although some are available inexpensively) and the relatively long time it takes to create the model. Depending on the size, it takes around 8 hours to create 3D models by evenly applying and curing silicone around the mold and dissolving the ABS in acetone. Therefore, it is necessary to devise more efficient ways of creating 3D models.
Conclusion
The use of a 3D silicone model in the preoperative examination allows for the selection of an appropriate WEB size, while avoiding the risk of bifurcation obstruction.
Acknowledgments
We would like to thank Editage (www.editage.jp) for the English language editing.
Ethics Statement
Ethics approval was not required for this study. Written informed consent was obtained from the patient.
The research within our submission has been approved by the Institutional Review Board of Saiseikai Fukuoka General Hospital.
Disclosure Statement
The authors declare that they have no conflicts of interest.
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