Use of Intermediate Guide Catheters as an Adjunct in Extracranial Embolization to Avoid Onyx Reflux into the Anastomotic Vasculature

Summary

Onyx is a non-adhesive polymer used for embolization of arteriovenous malformations and dural arteriovenous fistulas (DAVFs). The limiting factor for Onyx embolization is usually the amount of microcatheter reflux, which can be safely tolerated. The dual microcatheter technique, compliant balloon use proximally and the use of the dual lumen Scepter balloon have been described to prevent and limit proximal Onyx reflux. We describe the use the Navien 058 intermediate guide catheter to accept the Onyx reflux in its lumen and possibly also serve as a mechanical barrier to avoid reflux into the anastomotic channel connecting the occipital artery to the vertebral artery during DAVF embolization via the occipital artery. Complete embolization of the DAVF was achieved using the lumen of the Navien catheter to accept aggressive Onyx reflux. Complete cure of the DAVF was obtained with Onyx cast filling the entire venous pouch. Besides providing distal access support, intermediate guide catheters can also prevent embolic material reflux by accepting reflux into the lumen and providing a mechanical barrier.

Introduction

Onyx (ev3/Covidien, Irvine, CA, USA) is a cohesive non-adhesive polymer approved for preoperative embolization of pial arteriovenous malformations ¹. The non-adhesive nature of Onyx is useful for creating a plug at the tip of the microcatheter and then injecting Onyx distally once the proximal resistance is achieved. This, however, can also lead to the microcatheter getting stuck in the Onyx cast. Depending on the anatomy, there is a finite amount of reflux, which can be tolerated before the risk of microcatheter-related complications and the occlusion of normal arterial branches becomes high.

Previously, techniques like using a compliant balloon ^2,3, and the dual microcatheter technique ⁴ have been used to limit the reflux of Onyx. Recently, use of the Onyx-compatible Scepter balloon (MicroVention, Tustin, CA, USA) has also been described to inject Onyx with the balloon serving the purpose of flow arrest ^5,6. We describe a case in which the intermediate guide catheter was used to prevent reflux into the dangerous anastomotic channels connecting the occipital artery (OA) to the vertebral artery (VA). This technique does not replace current practices but gives an option during a few select cases of Onyx embolization when the reflux is reaching proximal branches in the extracranial circulation.

Technical Approach

A 56-year-old man presented for embolization with a symptomatic medial tentorial dural arteriovenous fistula. The meningeal branch of the OA, and the meningohypophyseal trunk of the ipsilateral carotid fed the DAVF. The fistulous point was into a venous ectasia with venous reflux into the deep venous system. Conventional angiography showed prominent opacification of the VA on injection of the OA via the posterior cervical branch and vice versa (Figure 1A,B). A 6F shuttle was placed into the common carotid artery, through which a 058 Navien intermediate guide catheter (ev3/Covidien, Irvine, CA, USA) was placed into the OA. The angiogram again showed opacification of the VA via the posterior cervical branch (Figure 2). Initial attempts to advance the intermediate catheter over a wire or a microcatheter to cover the origin of the posterior cervical branch were unsuccessful. A Marathon microcatheter (ev3/Covidien, Irvine, CA, USA) was advanced as close as possible to the venous ectasia. Detachable microcatheters are not FDA-approved for use in US, hence were not used. The rationale to use Onyx instead of glue was to deliberately try to close the venous ectasia and then reflux the embolic material back to the meningohypophyseal trunk. After prepping with DMSO, Onyx 34 was slowly infused by the “plug and push” technique (Figure 3). Onyx 34 was used due to physician preference and better control on the antegrade flow of the embolic material. However, the Onyx reflux reached the main OA before the entire DAVF could be embolized. At this point, given the proximity of the posterior cervical branch and the anastomosis with the VA, rather than accepting more reflux into the occipital artery, the intermediate guide catheter was advanced into the ostium of the meningeal branch of the OA (Figure 4). This was possible this time over the embedded Marathon microcatheter within the Onyx cast, over which the Navien 058 catheter was advanced. Thereafter, continuation of the Onyx injection showed reflux into the Navien guide catheter rather than the OA (Figure 4). This was at all times confirmed by an orthogonal view (Figure 5). This is extremely important to be sure that the Onyx reflux is intraluminal and not on the outside and subsequently around the intermediate catheter. Complete embolization of the DAVF was performed using the lumen of the Navien to accept aggressive Onyx reflux. Complete cure of the DAVF was obtained with Onyx cast filling the entire venous pouch. At the end of the procedure, the Marathon microcatheter and the Navien were removed under constant aspiration. No intraprocedural complications were noted. Post-embolization angiograms demonstrated no reflux of Onyx into the posterior cervical branch of the OA. The Onyx cast served as the distal stabilizing point over which the intermediate catheter could be advanced even if it was not possible previously. The intermediate catheter served a dual purpose: to accept the Onyx reflux into the lumen and possibly also to provide a mechanical barrier at the origin of the posterior cervical branch. This is only possible with magnification under high quality fluoroscopy is orthogonal planes with attention to the Onyx cast and to make sure the Onyx is inside the catheter and not external to the intermediate catheter. This technique is an option during extracranial embolic embolization in a few select cases.

Figure 1.

Frontal (A) and lateral (B) left vertebral artery (VA) angiograms demonstrate the prominent connection between the VA and the external carotid artery (ECA) via the posterior cervical artery (PCA) (arrow). Note opacification of the DAVF.

Figure 2.

Lateral ECA angiogram shows the PCA (small arrow) and the meningeal branch opacifying the DAVF. Note the location of the tip of the Navien 058 guide catheter (large arrow).

Figure 3.

Lateral ECA angiogram during embolization with Onyx at the ostium of the feeding artery (double arrows). Note the PCA (small arrow) and the location of the tip of the Navien 058 guide catheter (large arrow).

Figure 4.

Non subtracted lateral (A) and oblique (B) images show the Onyx cast at the ostium of the feeding artery (triple arrows) Note the new position of the Navien intermediate guide catheter after advancing over the microcatheter-Onyx cast (arrow). Also note the reflux of Onyx into the guide catheter (star). Inset in A: magnified image showing the Onyx cast within the Navien (star). Note the Onyx cast filling the venous pouch indicating complete obliteration of the DAVF (double arrows).

Figure 5.

Post-embolization lateral ECA angiogram shows non opacification of the DAVF with a patent PCA (arrow).

Conclusion

Intermediate guide catheters are usually used for Onyx embolization to provide support for distal access, improved vector of pull for the microcatheter after embolization, and for selective angiograms. This short case report also demonstrates, anatomy permitting, that the newer generation of more navigable intermediate guide catheters can also prevent embolic material reflux by either accepting the reflux within the lumen or by providing a mechanical barrier during extracranial embolization.