Introduction

Effective coil embolization of ruptured wide-neck intracranial aneurysms with unfavorable morphology remains challenging owing to the limited applicability of stents and the consequent need for dual antiplatelet therapy (DAPT) in the setting of subarachnoid hemorrhage (SAH).1 Balloon-assisted temporal neck bridging during intrasaccular coil delivery has been a well-established technique for treatment of these lesions as a better choice to permanent stent implantation.2 3 However, the inevitable occlusion of the parent vessel associated with this technique, poses risks of ischemic complications due to compromised downstream perfusion, blockage of perforators, and thrombus formation during the balloon inflation.4 5 The application of devices offering temporal neck bridging, while maintaining parent vessel patency during coil embolization, has recently emerged as a new and attractive alternative to placement of occlusive balloons.6–8 Here, we describe our initial experience with the recently introduced Cascade non-occlusive neck bridging device in the treatment of ruptured wide-neck intracranial aneurysms.

Materials and methods

Cascade is a new non-occlusive fully retrievable neck bridging device, designed to provide temporary support during coil embolization of intracranial aneurysms. This braided device is composed of 42 interwoven nitinol and platinum wires, forming a net-like compliant structure with variable cell porosity that persistently maintains a cell size of <0.3 mm² (figure 1). The ultra-thin wire braid structure is produced in a specific way to allow easy adjustment of the braid through controlled expansion and partial resheathing, providing a working length of 37 mm while the braid is fully collapsed, and 10 mm while fully expanded. Optimal neck coverage is achieved by actively adjusting both the diameter (0.5–6 mm, controlled by handle manipulation) and length (by partial unsheathing or resheathing) of the braided net. The platinum wires allow visibility of the device. Both ends of the device include radiopaque markers for its optimal visibility and precise positioning. The device is delivered in a collapsed form through a microcatheter and subsequently expanded via a control handle. The control handle has two modes: (1) auto-lock (‘ratchet’) mode for stepwise radial expansion, and (2) continuous mode for more smooth and gradual expansion that can also provide tactile feedback. A small radiopaque atraumatic soft tip extends from the distal end of the device, designed for improved visibility, trackability, and anatomic orientation. Figure 2 illustrates all components of the device. Cascade is compatible with a 021 microcatheter and is available in two sizes: (1) M—recommended vessel diameter 2–4 mm; and (2) L—recommended vessel diameter 4– 6 mm. The device received a CE mark of approval in the third quarter of 2018.

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Figure 1

Drawing of Cascade methodology: the device is expanded across the neck of a basilar tip aneurysm to provide temporary support during coil embolization.

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Figure 2

Cascade: schematic drawing of all device components.

In this single-center study, we present our initial experience with this new device in the treatment of ruptured intracranial aneurysms, focusing on aneurysm obliteration, parent vessel interaction, and thromboembolic complications.

We performed retrospective analysis of prospectively collected data. Between May 15 and June 30, 2019, a total of 12 patients with aneurysmal SAH underwent coil embolization in conjunction with Cascade in our center. All patients were selected based on aneurysm characteristics, which included aspect ratios ≤1.2, and/or unfavorable aneurysm morphology associated with a high risk of potentially non-satisfactory obliteration after primary coiling as deemed by the primary operator. The following baseline characteristics were recorded: patient age, gender, clinical presentation (Hunt and Hess grade), SAH volume and extension (Fisher grade), aneurysm location, aneurysm dome size, aneurysm neck size. Technical, angiographic, and clinical variables included the type of Cascade device used, duration of time during which the device remained expanded (device expansion time), aneurysm obliteration (Raymond’s scale), clinical complications (any neurologic deterioration from the immediate postoperative period until discharge, signs and symptoms of rerupture, or death), technical complications (intraoperative aneurysm rupture, parent vessel perforation, device-induced dissection, device thrombosis, distal emboli, device-induced spasm, coil entanglement) (table 1).

Procedural and technical details 

Written informed consent was obtained from every patient and their relatives before each endovascular session according to local institutional policy. The decision to perform each endovascular embolization was based on consensus by the institutional multidisciplinary team of interventional neuroradiologists, neurologists, and neurosurgeons. All procedures were performed under general anesthesia on a biplane angiographic unit (Innova GE Healthcare 31 31 IQ biplane). The patient’s systolic blood pressure during and after the procedure was controlled and maintained between 90 and 120 mm Hg in order to prevent aneurysm rerupture before satisfactory obliteration. Nine of 12 (75%) lesions were accessed through distal radial access, and right femoral access was used in three patients. After completion of diagnostic angiography, the diagnostic catheter was exchanged over an exchange-length wire for a 6 French Softip XF guide catheter. In general, the guide catheter was positioned in the pre-petrous portion of the internal carotid artery or distal cervical vertebral artery segment and connected to a pressurized infusion bag of normal saline containing 10 mL of nimodipine solution and 5000 IU of heparin. A 3-dimensional angiogram was obtained and postprocessed at a separate station. Once the aneurysm morphology was evaluated, a 0.021 inch microcatheter (Headway 21 or Rebar 18) was navigated into the parent vessel just distal to the aneurysm location. Next, a 0.010 inch microcatheter (Echelon 10) was used to catheterize the aneurysm.

Once the aneurysm was catheterized, the Cascade device was introduced into the 0.021 inch microcatheter and deployed across the jailed 0.010 inch microcatheter covering the aneurysm neck. The device was deployed in its collapsed shape by completely unsheathing the microcatheter. Next, the Cascade was inflated/expanded using the control handle attached to the proximal shaft of the device. Similar to other braided stents, the Cascade has variable porosity, which is proportional to the device elongation and foreshortening, and controlled via the handle. Thus, targeted overexpansion and/or denser neck coverage was employed to achieve the desired aneurysm obliteration in selected cases. The device was collapsed before detachment of the initial framing coil to ensure stable intra-aneurysmal positioning and no parent vessel protrusion. Once stable framing coil positioning was ensured, the device was re-expanded. The handle was locked once satisfactory expansion and aneurysm neck coverage was achieved. Next, sequential coil delivery was performed through the jailed microcatheter (figure 3). Multiple control angiograms were obtained during the coil embolization, while the device remained expanded across the aneurysm neck. Special attention was paid to device thrombosis, distal emboli, parent vessel dissection, and distal tip-induced spasm. Once satisfactory obliteration was achieved, the device was deflated/collapsed under live fluoroscopy to assess coil mass stability. A final control angiogram was obtained before detaching the last coil.

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Figure 3

A 5 mm ruptured anterior communicating artery aneurysm with a small daughter sac (A and B). Cascade size M was deployed across the aneurysm neck (C). The black arrow points to the distal tip of the device. The white arrow points to the jailed microcatheter, which is positioned in the aneurysm sac. Final postinterventional angiogram shows complete obliteration with widely patent parent vasculature (D).

Results

Of the 12 treated patients, 41.7% (5/12) were female, the median age was 55 (47–77), the median aneurysm dome size was 5.75 mm (3–9.1), and the median neck size was 3.55 mm (2.3–7.9). Details of the procedural results and patients’ characteristics are listed in table 1. Complete obliteration (Raymond 1) was achieved in 75% (9/12) of all cases. In three of the 12 cases (25%), residual neck (Raymond 2) was left intentionally in order to avoid ischemic complication due branch occlusion. None of the patients received any oral or intravenous antiplatelet therapy perioperatively for the prevention of thrombotic complications. As indicated in the procedural and technical details, no additional intravenous heparin was given beyond the standard dose used in our institution for all interventional procedures. No technical difficulties of inflation/expansion and retraction/deflation associated with the control handle occurred. No evidence of thrombus formation was seen during device deployment as shown by multiple control angiograms. Additionally, no evidence of distal emboli on the final angiograms was seen. No device-related spasm, vessel perforation, or coil entanglement was detected. The distal tip remained straight with no evidence of deflection or interaction with the parent vessel during device expansion. Overall, no technical or clinical complications were observed.

Discussion

Many endovascular techniques for treatment of intracranial aneurysms have emerged since the introduction of the revolutionary coil embolization as a superior methodology to surgical clipping.9 From the inception of the first coiling procedure to the most recently advanced technology, the aneurysm embolization methodology relies on the principle of quick intra-aneurysmal thrombosis with subsequent endothelialization across the neck and restoration of normal parent vessel anatomy.10 11 This healing effect can be achieved by intra-aneurysmal filling and/or flow diversion through various intrasaccular and neck covering devices.12

Coiling remains the most commonly used intrasaccular treatment, with predictable clinical and angiographic outcomes and safety, especially in cases with favorable anatomy. However, effective coil embolization of wide-neck intracranial aneurysms (WNAs) with low aspect ratios remains challenging owing to a high probability of perioperative complications and post-treatment recurrence. This often requires adjunctive neck bridging devices to support the intrasaccular coils and/or provide flow diversion effect.13–15 Despite the more durable effect of permanent stenting, the risk of thromboembolic complications remains a considerable limitation and requires a 3–6 month course of DAPT, which has its own independent hemorrhagic risk.16 These limitations associated with stent-assisted coiling and flow diversion are particularly relevant in patients with ruptured WNAs. SAH is independently associated with high thrombotic risk and also limits the applicability of DAPT, especially in the presence of a ventriculostomy drain.17 Balloon remodeling is a well-established treatment of ruptured WNAs and a reasonable alternative to stenting.3 However, the parent vessel occlusion associated with this balloon-assisted embolization, poses serious risks of ischemic complications due to compromised downstream perfusion, blockage of side-wall perforators at the occluded segment, and thrombus formation during the balloon inflation.4 5 Given these serious disadvantages, other alternative technical solutions for endovascular treatment of WNAs have emerged in recent years. The main goal of these new techniques is to reduce the complexity of the procedure, improve obliteration rates, and reduce the amount of metal in the parent vessel. One such method is the placement of a temporal neck bridging device, which allows parent vessel flow during intrasaccular embolization.6 Recent clinical experience with the Comaneci temporal neck bridging device demonstrated that this methodology can result in satisfactory and durable embolization.8

The Comaneci device (Rapid Medical, Israel) is similar to Cascade. However, the two main distinguishing technical features of Cascade as compared with Comaneci are its denser aneurysm neck coverage and the absence of device/distal tip deflection during expansion (figure 4). Based on our experience with over 100 patients treated with Comaneci, these technical features are important differences in performance during embolization, including device deflection-induced spasm, coil entanglement, and navigability. It is important to emphasize that these observations are based only on personal opinion and do not represent statistically validated conclusions. As noted during the initial experience with Comaneci, deflection of the device (and particularly its distal tip) can produce significant nearly occlusive spasm during expansion.8 We did not observe this phenomenon in the present case series with the Cascade. We also noted excellent compliance with the parent vessel geometry during expansion. Another much less frequent, but also important concern associated with Comaneci is occasional coil entanglement, requiring careful manipulation and close observation during device expansion and retraction. Coil entanglement was not noted in our experience with Cascade, probably owing to the braid composition with denser net and more robust aneurysm neck coverage. This unique feature of the device can also explain the temporal intra-aneurysmal flow stagnation observed in one of the cases, which may promote accelerated aneurysm thrombosis in conjunction with coiling (figure 5).

Conversely, an important advantage of Comaneci over Cascade is its compatibility with a 0.017 inch microcatheter, allowing smoother navigation in tortuous anatomy. The current version of Cascade is compatible only with 0.021 inch or larger internal diameter microcatheters. In some patients with more prominent tortuosity, there was notable tension on the entire system during introduction of the device within the microcatheter. In those cases, placement of smaller profile device would have been preferred for ease of navigability. Nevertheless, all devices in our series were navigated and deployed successfully without any technical complications.

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Figure 4

Cascade versus Comaneci in their expanded versions. Cascade remains straight (thin arrow), whereas Comaneci (thick arrow) deflects during expansion. Cascade has a visibly denser net than Comaneci.

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Figure 5

A 6 mm left para-ophthalmic ruptured intracranial aneurysm (A). Cascade L was placed across the neck and temporarily expanded (B). Significant intra-aneurysmal flow stagnation was noted immediately after device expansion (C). The device was then collapsed, and the aneurysm was catheterized (D). The device was re-expanded, followed by coil embolization through the jailed microcatheter (E). Complete obliteration was achieved (F).

Conclusions

In our initial experience, Cascade is a safe and effective tool for adjunctive coil embolization of ruptured WNAs with no evidence of periprocedural device-related complication and an acceptable occlusion rate. However, larger multicenter series with long-term follow-up data are needed to confirm the clinical benefit of this new device.