How to WEB: a practical review of methodology for the use of the Woven EndoBridge

Abstract

Wide-necked bifurcation aneurysms (WNBAs) make up 26-36% of all brain aneurysms. Treatments for WNBAs pose unique challenges due to the need to preserve major bifurcation vessels while achieving a durable occlusion of the aneurysm. Intrasaccular flow disruption is an innovative technique for the treatment of WNBAs. The Woven EndoBridge (WEB) device is the only United States Food and Drug Administration approved intrasaccular flow disruption device. In this review article we discuss various aspects of treating WNBAs with the WEB device, including indications for use, aneurysm/device selection strategies, antiplatelet therapy requirement, procedural technique, potential complications and bailouts, and management strategies for residual/recurrent aneurysms after initial WEB treatment.

Keywords: aneurysm; device; flow diverter; technique.

Figure 1

Woven EndoBridge (WEB) devices: (A) Double Layer (DL); (B) Single Layer (SL); and (C) Single Layer Sphere (SLS). The WEB DL EV is a mesh sphere composed of 2 layers of braided nitinol/platinum wires. The inner and outer layers of braid are joined by proximal, middle, and distal platinum/iridium markers. The WEB SL EV and WEB SLS EV models are composed of single layers of braided nitinol. The braids are joined at the proximal and distal ends of the device by radiopaque platinum/iridium markers.

Figure 2

(A) Digital subtraction angiogram (DSA) of a patient with an incidental basilar apex aneurysm presented for WEB treatment demonstrating superiorly and upward projecting wide-necked basilar apex aneurysm. (B) There is a minimal angle between parent artery and aneurysm long axis (solid red line), making this an ideal case for WEB embolization. (C) Native DSA demonstrating successful deployment of the WEB within the aneurysm. (D) A patient with an incidental basilar apex aneurysm projecting superiorly and posteriorly, presented for WEB treatment. (E) There is an obtuse angle between parent artery and aneurysm long axis (solid red line), which requires extra attention when deploying a WEB device to avoid excessive friction between the device and the back wall of the aneurysm. (F) Native DSA demonstrating successful deployment of the WEB within the aneurysm.

Figure 3

(A) A patient with a prior history of subarachnoid hemorrhage caused by rupture of a posterior communicating artery aneurysm presented for WEB treatment of an enlarging unruptured basilar apex aneurysm. (B) Post-deployment native digital subtraction angiogram (DSA) demonstrating adequate positioning of the WEB SL within the aneurysm. (C, D) Post-detachment native DSA demonstrating change in orientation of the deployed WEB device causing mild impingement of the left posterior cerebral artery. A decision was made to deploy a LVIS stent (MicroVention, Terumo, Tustin, California, USA) to protect the left posterior cerebral artery. (E, F) Post-deployment flat panel cone-beam CT with reconstruction of the LVIS stent showing the WEB device within the aneurysm and patent LVIS stent spanning from the left posterior cerebral artery into the basilar artery.

Figure 4

Three-dimensional (A, B) and two-dimensional (C, D) angiographic images of an incidental anterior communicating artery aneurysm prior to WEB treatment. The lateral three-dimensional (B) and two-dimensional (D) projections represent the 'down the barrel' view of the anatomyof the branch arteries so that an appropriately sized WEB device can be selected.

Figure 5

(A) Two identical SLS 7 WEB devices are shown. (B) One device was placed into a 6 mm tube, resulting in adequate compression and corresponding lengthening of the height of the device by 1 mm. The second device was placed into a 10 mm tube and was therefore not under lateral compression. (C) Identical weights were loaded onto the devices. The compressed WEB is able to maintain its shape under the load while the WEB that is not laterally compressed cannot maintain its shape.

Figure 6

Different sizes of WEB SL and SLS devices available based on aneurysm sizes from Microvention’s library (note that the WEB 17 system is not approved in the USA). Top: WEB SL device selection table. Bottom: WEB SLS device selection table.

Figure 7

(A–F) Because the microcatheter is against the back wall of the aneurysm, deployment of the WEB device via progressive unsheathing of the microcatheter and pinning the delivery wire is employed. This method allows the device to open without applying dangerous distal marker point force against the aneurysm wall. (G, H) Once the device is sufficiently open, it is soft enough to be repositioned within the aneurysm by advancing the pusher wire, which allows the WEB to better conform to the entire circumference and seal the neck. (I) Note that the axis of the device has been rotated in a counter clockwise fashion by this final maneuver (curved arrow). (J) Follow-up digital subtraction angiogram at 12 months demonstrating complete embolization of the aneurysm.

Figure 8

(A) Digital subtraction angiogram (DSA) demonstrating an unruptured left middle cerebral artery bifurcation aneurysm (5.4 mm wide × 6.3 mm high) prior to WEB treatment. An 8 mm × 3 mm WEB SL device was chosen for the treatment. (B, C) Post-deployment native DSA of the WEB device and (B) native program DSA demonstrating (C) the laterally compressed WEB device within the aneurysm without compromise of the branch vessel. Note that the width of the compressed WEB device is now 5.77 mm (decreased from 8 mm) with a height of 4.08 mm (increased from 3 mm).

Figure 9

(A) Post-deployment standard Neuro native digital radiography imaging without contrast of WEB device. (B) Standard Neuro native digital radiography imaging with contrast. (C) WEB native digital radiography imaging without contrast and (D) with contrast, enhancing the visualization of the WEB device.

Figure 10

(A) A patient with an incidental left middle cerebral artery (MCA) bifurcation aneurysm presented for WEB treatment. (B) Post-deployment standard digital subtraction angiogram (DSA) run demonstrating the proximal and distal markers of a deployed WEB SL device. (C) Post-deployment special WEB native program DSA run without and (D) with contrast, allowing better visualization of the device. (G) Dual volume three-dimensional DSA showing the shape of the deployed WEB device and its relationship with surrounding branch vessels.

Figure 11

(A) A patient presented for WEB treatment of an incidentally detected anterior communicating artery (ACA) aneurysm. (B) Post WEB SL detachment digital subtraction angiogram (DSA) showed adequate positioning of the WEB device within the aneurysm. While removing the VIA microcatheter, the inside of the catheter tip was brushed by the stem of the WEB, leading to backward movement of the WEB. (C) Follow-up native DSA demonstrating migration of the WEB device within the parent ACA. The decision was made to push the WEB device with the microcatheter and wire. (D) The WEB device was pushed within the aneurysm, as evidenced by the movement of proximal and distal markers. (E) Follow-up native angiography demonstrating adequate position of the WEB within the aneurysm. (F) Six-month follow-up DSA showing complete occlusion of the aneurysm.

Figure 12

(A) A patient with an incidentally detected unruptured basilar apex aneurysm presented for WEB treatment. (B) Immediately after unsheathing a proximal Double Layer (DL) device, the microcatheter was advanced distally into the proximal aspect of the aneurysm. Follow-up digital subtraction angiogram (DSA) demonstrated a small amount of active contrast extravasation from the aneurysm dome. (C) Heparinization was reversed with protamine and a Hyperform 4 mm × 7 mm balloon (Medtronic, Irvine, California, USA) was transiently inflated within the distal basilar artery. (D) Repeat angiography demonstrated resolution of the extravasation. (E) Native DSA performed post-detachment demonstrating the WEB device well compressed in the aneurysm, leading to complete occlusion of the aneurysm without any branch vessel compromise. (F) Post-treatment flat panel cone-beam CT head showing a small amount of contrast extravasation within the interpeduncular cistern. The patient experienced no neurological sequelae from the transient extravasation.

Figure 13

Web Occlusion Scale grades A and B indicate complete occlusion (A) with or (B) without an angiographically visible collection of contrast within the marker recess. (C) Residual neck filling is indicated by contrast opacification of the aneurysm neck extending beyond the expected bounds of the marker recess. (D) Residual aneurysm filling is indicated by contrast opacification extending beyond the aneurysm neck and into the fundus, either deep to the proximal marker recess or around the periphery of the device.

Figure 14

(A) A patient presented for WEB treatment of an incidentally detected basilar apex aneurysm. (B) Post-detachment digital subtraction angiogram (DSA) of the WEB SL demonstrating adequate positioning of the WEB within the aneurysm. (C) Native DSA demonstrating adequate compression of the WEB within the aneurysm without any compromise of branch vessels. (D) Six-month follow-up native DSA demonstrating WEB compression caused by deepening of the device recesses at both sides, resulting in a neck residual.

Figure 15

(A) A patient with an incidental basilar apex aneurysm presented for elective WEB treatment. (B) Immediate post-deployment digital subtraction angiogram (DSA) demonstrating adequate deployment of the WEB within the aneurysm. (C) Six-month follow-up DSA showing WEB compression and neck remnant. (D) Two-year follow-up DSA showing growing neck remnant. The decision was made to proceed with stent-assisted coiling of the neck remnant. (E) Immediate post-retreatment native DSA demonstrating coil mass within the neck remnant and stent spanning from the left posterior cerebral artery into the basilar artery. (F) Six-month follow-up native DSA.