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. Author manuscript; available in PMC: 2021 Jun 21.
Published in final edited form as: World Neurosurg. 2020 Mar 13;139:111–120. doi: 10.1016/j.wneu.2020.02.101

Woven Endobridge (WEB) Device as a Retreatment Strategy After Unsuccessful Surgical Clipping

Thomas C Booth 1,2,✉, Carmen Parra-Farinas 3, Ruth-Mary deSouza 4, Naga Kandasamy 2, Jo Bhattacharya 5, Prem Rangi 6, Jonathan Downer 7
PMCID: PMC7611019  EMSID: EMS124477  PMID: 32179191

Abstract

Background

Surgical clipping of intracranial aneurysms is typically robust and durable. However, residual aneurysmal components may be seen after clipping. Furthermore, there may be occasional aneurysmal recurrence. These factors are both clinically relevant because subarachnoid hemorrhage after clipping is a rare but important event. The rationale for any treatment is to substantially decrease the future risk of hemorrhage. Small series have shown coiling as a retreatment strategy after unsuccessful clipping, but none has explored the feasibility of Woven Endobridge (WEB) implantation.

Case Description

We examined the feasibility of WEB implantation as second-line treatment for wide-necked residual aneurysms after unsuccessful clipping. We also recorded the safety and efficacy in this small series of 6 patients. To determine safety, we measured the modified Rankin Scale score before and after the procedure, and at 2 later time points (mean follow-up, 5 months and 15 months). To determine efficacy, we obtained radiographic aneurysm occlusion outcomes (including WEB Occlusion Scale) at these 2 time points. Four middle cerebral artery and 2 anterior communicating artery complex aneurysms were treated with WEB implantation, showing feasibility in 6/6 cases (100%). Follow-up at 15 months showed no change from preprocedural modified Rankin Scale score and there were no other complications. There was adequate occlusion in 5/6 cases (83%).

Conclusions

WEB implantation provided a feasible option in this challenging retreatment scenario. This is a small series and prospective data are required to make outcome inferences for this population. Nonetheless, we observed no complications and high adequate occlusion rates.

Keywords: Aneurysm remnant, Endovascular treatment, Intrasaccular device, Recurrent aneurysm, Residual aneurysm, Surgical clipping, Woven Endobridge (WEB)

Introduction

Surgical clipping of intracranial aneurysms is typically robust and durable; however, a residual aneurysmal component may be seen after clip placement in up to 4%–8% of cases.1–6 Furthermore, in 1%–3% of cases, there may be aneurysmal recurrence.5–7 These are both clinically relevant occurrences because there is a persistent risk of rupture or rerupture.3,5,8,9 Subarachnoid hemorrhage from remnants after surgical clipping is poorly quantified but may occur in 0.8% of cases per annum.1–3 The rationale for any treatment is to substantially decrease the future risk of hemorrhage and therefore retreatment of residual or recurrent aneurysms is frequently indicated. A third scenario for retreatment occurs when a clip cannot be placed safely and the surgeon judiciously elects to abandon the procedure.1 In all 3 scenarios’ retreatment with clipping seems to be associated with an increased rate of complications.1,10 Endovascular retreatment seems to have a lower rate of complications and has become more common in the last 2 decades.9 However, many aneurysms that recur are wide-necked and are therefore challenging to treat by endovascular coiling alone because of the risk of coil protrusion into the parent vessel.11,12 A definitive retreatment strategy has not been established and aneurysms are managed on a case-by-case basis. In this context, the Woven Endobridge (WEB [Sequent Medical, Aliso Viejo, California, USA]) device might emerge as an endovascular retreatment option in selected cases. It has recently been shown in a small series that retreatment of recurrent, previously coiled aneurysms with WEB implantation is feasible and may be safe and effective.13 The WEB is a nitinol, braided-mesh, selfexpanding, intrasaccular flow-disrupter with a three-dimensional (3D) structure primarily designed to occlude wide-neck intracranial aneurysms. The second-generation WEB consists of a single-layer compartment that impedes aneurysmal neck blood flow, resulting in intra-aneurysmal thrombosis and subsequent endothelialization. Since its introduction in 2011, several single-arm studies have shown that the WEB seems safe (low morbidity and mortality) and effective (high adequate occlusion rates) when used as a first-line implant to treat wide-neck ruptured and unruptured aneurysms.14–21 Although small series have reported coiling as a retreatment strategy after unsuccessful clipping,9 no series has explored the feasibility of WEB implantation. We describe the feasibility of WEB for retreatment of wide-neck aneurysms after surgical clipping has been unsuccessful. We report the combined experience of 4 centers and present safety (morbidity and mortality) and efficacy (occlusion rates) outcomes.

Case Description

Methods

We searched medical records for patients with residual aneurysms that were treated with WEB after unsuccessful surgical clipping between January 2014 and January 2016 at 6 United Kingdom hospitals. For each patient included in the study, we retrospectively analyzed the electronic medical records; preprocedural, procedural, and postprocedural images; as well as procedural records. We collected demographic, radiologic, and clinical data on an intention-to-treat basis. The presence of a residual aneurysm was confirmed on follow-up digital subtraction angiography (DSA) and/or 3D time-of-flight (TOF) magnetic resonance angiography (MRA) (MRA). The diameter of any residual aneurysmal sac and neck was measured.

WEB implantation for all cases was chosen after a consensus decision at a neurovascular multidisciplinary team meeting, which included interventional neuroradiologists and neurovascular surgeons. Anatomic characteristics (including location, a high neck/sac ratio, and a wide neck), safety and technical concerns, and the role of antiplatelets were the main factors leading to WEB implantation in preference to coiling, stent-assisted coiling, or further clipping.

Interventional neuroradiologists performed all procedures under general anesthesia using a femoral approach. Anticoagulation and antiplatelet therapies were administered according to local institutional protocol.

To determine safety, we recorded the modified Rankin Scale (mRS) score before and after the procedure and at follow-up at 2 later time points. Ischemic and hemorrhagic complications were analyzed. Imaging follow-up was performed with DSA (with additional cone-beam computed tomography angiography in some centers), or3DTOF MRA (AERA 1.5 T [Siemens Healthcare GmbH, Erlangen, Germany]) with repetition time, 25 milliseconds; echo time, 7 milliseconds; flip angle, 25 (with ramped pulse); matrix, 241 × 256; field of view, 18 × 18 cm; and slice thickness, 1.4 mm (reconstructed to 0.5 mm). To determine efficacy, aneurysm occlusion status was classified using the WEB Occlusion Scale (WOS).22 Opacification of the WEB device recess (WOS score 2) was considered complete occlusion.

Written informed consent was obtained from all patients. We received written confirmation from the Research and Innovation Department at King’s College Hospital that the United Kingdom Health Research Authority does not require review by a research ethics committee given the nature of the retrospective study using de-identified data. The study was performed in accordance with the ethical standards laid down in the i964 Declaration of Helsinki and its later amendments.

Results

Six patients from 4 hospitals with residual bifurcation aneurysms after unsuccessful surgical clipping were retreated with WEB implantation. The causes for unsuccessful surgical clipping were the decision to abandon the procedure because of the presence of a mixed atheromatous and calcified plaque at the aneurysmal neck extending into the temporal M2 segment, which might cause emboli as well as temporal M2 segment occlusion if clipped (patient 1; Figure 1); inability to create a dissection plane surrounding the aneurysm because it was adherent to the surrounding structures making clip placement technically challenging and unsafe (patient 2); inability to safely dissect free the origins of the M2 branches that arose from the aneurysm neck, increasing the risk of occluding an M2 branch (patient 3). These 3 aneurysms were wrapped with muslin pending further retreatment. Suboptimal clip placement resulted in inadvertent incomplete clipping in patients 4 (Figure 2), 5 (Figure 3), and 6 (Figure 4) despite indocyanine green angiography seeming to show satisfactory clip positioning. In patient 4, the procedure was complicated by impaired visualization of the neck branches and a bloody operative field. Baseline patient characteristics and initial aneurysm features are summarized in Table 1.

Figure 1.

Figure 1

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An aneurysm that was retreated with Woven Endobridge implantation after an unsuccessful attempt at surgical clipping (patient 1). A patient in their 50s presented with a single seizure. They were hypertensive, had chronic obstructive pulmonary disease, and had a 40-pack per year smoke history. A left middle cerebral artery bifurcation aneurysm was discovered on magnetic resonance imaging and characterization with computed tomography angiography showed a partially thrombosed, 21-mm (maximal diameter) aneurysm with a 5-mm-wide neck (A and B). The decision of the neurovascular multidisciplinary team and patient was for surgical clipping. A mixed atheromatous and calcified plaque at the aneurysmal neck extending into the temporal M2 segment that was seen at surgery (C) prevented safe clipping because of the risk of emboli and the risk of occlusion of the temporal M2 segment. Muslin wrapping was performed instead. The aneurysm was unchanged on digital subtraction angiography, and after multidisciplinary team and patient discussion, the patient underwent Woven Endobridge implantation 3 months later. A 6-F Shuttle catheter (Cook Medical, Bloomington, Indiana, USA), a 1.83-mm (0.072 in) Navien intracranial support catheter (Medtronic, Dublin, Ireland) and a 0.69-mm (0.027 in) Via microcatheter (Microvention, Tustin, California, USA) were used to deploy a single-layer 6-mm (width) × 4-mm (height) WEB single-layer device into the neck of the aneurysm as a cork (D). Adjunctive coils were placed into the distal sac (D) through a 1.7-F Echelon-10 microcatheter (Medtronic). Aspirin 75 mg by mouth once daily was given before, during, and after all procedures (prescribed independently for cardiovascular risk). Heparin was given at the beginning (5000 IU intravenously [IV]), end (3000 IU IV), and after the procedure (1000 IU/hour IV over 20 hours). Complete occlusion of the aneurysm was shown at the end of the procedure with normal filling of the left middle cerebral artery circulation. There were no complications periprocedurally or during 18 months follow-up. Six and 18 months check three-dimensional time-of-f light magnetic resonance angiography confirmed persisting complete occlusion. SL, single layer.

Figure 2.

Figure 2

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An aneurysm that was retreated with Woven Endobridge (WEB) implantation after incomplete surgical clipping (patient 4). A patient in their 50s was referred for treatment after incidental discovery of a right middle cerebral artery bifurcation aneurysm. The patient was hypertensive and a smoker. Cone-beam computed tomography angiography (DynaCTA) showed an 8-mm (maximal diameter) aneurysm with a 6-mm-wide neck (A). The decision of the multidisciplinary team and patient was for surgical clipping. The procedure was complicated by difficulty of clip placement because of impaired visualization of neck M2 branches and a bloody operative field. Intraoperative fluorescence angiography showed that neck coverage, although incomplete, gave adequate occlusion. The patient developed an ischemic infarct within the operated territory. (B) Follow-up digital subtraction angiography showed that the aneurysm remained almost identical. The case was reassessed in the multidisciplinary team and after discussion with the patient, WEB implantation was planned 2 months after clipping. A 6-F Envoy catheter (Codman, Raynham, Massachusetts, USA), a 1.47-mm (0.058 in) Navien intracranial support catheter (Medtronic, Dublin, Ireland) and a 0.69-mm (0. 027 in) Via microcatheter (Microvention, Tustin, California, USA) were used to deploy a single-layer 7-mm (width) × 5-mm (height) WEB single-layer device (C). The patient was commenced on aspirin 150 mg by mouth once daily and clopidogrel 150 mg by mouth once daily for 3 days before the procedure. 5000 IU heparin intravenously was given at the beginning of the procedure. Complete occlusion of the aneurysm was shown at the end of the procedure with normal filling of the right middle cerebral artery circulation (C). There were no new complications periprocedurally or during 24 months follow-up. Six and 24 months check cone-beam computed tomography angiography confirmed persisting complete occlusion.

Figure 3.

Figure 3

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An aneurysm in which the morphology changed after incomplete surgical clipping allowing retreatment with Woven Endobridge (WEB) implantation (patient 5). A patient in their 50s presented with a World Federation of Neurosurgeons grade 1 subarachnoid hemorrhage caused by a ruptured 9-mm (maximal diameter) right middle cerebral artery bifurcation aneurysm with a 5-mm neck, shown here on an computed tomography angiography reformat (A). The decision of the multidisciplinary team and patient was for surgical clipping. Surgery was performed using intraoperative fluorescence angiography and the clipping was uneventful. (B) However, at 2 months digital subtraction angiography follow-up, there was a 4-mm (maximal diameter) aneurysm remnant with a 4-mm-wide neck, shown here as an unsubtracted image, for which the morphology was more suitable for WEB implantation. The case was reassessed in the multidisciplinary team and after discussion with the patient, WEB implantation was performed. A 6-F Benchmark catheter (Penumbra, Alameda, California, USA) and a 0.53-mm (0.021 in) Via microcatheter (Microvention, Tustin, California, USA) was used to deploy a single-layer 5-mm (width) × 3-mm (height) WEB single-layer device (C). The patient was commenced on aspirin 300 mg aspirin and clopidogrel 300 mg the evening before and the morning of the procedure. 5000 IU heparin intravenously was given at the beginning of the procedure. (D) Adequate occlusion of the aneurysm was shown at the end of the procedure with normal filling of the right middle cerebral artery circulation. There were no new complications periprocedurally or during 24 months follow-up. Six and 8 months digital subtraction angiography confirmed persisting adequate occlusion.

Figure 4.

Figure 4

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An aneurysm for which the size changed after incomplete surgical clipping allowing retreatment with Woven Endobridge (WEB) implantation (patient 6). A patient in their 60s presented with a World Federation of Neurosurgeons grade 1 subarachnoid hemorrhage caused by a ruptured 11 mm (maximal diameter) anterior communicating artery complex bifurcation aneurysm with an 8-mm neck, shown here on a computed tomography angiography reformat (A). The decision of the multidisciplinary team and patient was for surgical clipping. Surgery was performed using intraoperative fluorescence angiography and the clipping was uneventful. (B) However, at 7 days digital subtraction angiography follow-up, there was a 4-mm (maximal diameter) aneurysm remnant (arrow) with a 4-mm-wide neck, shown here as a cone-beam computed tomography angiography reformat (clip is purple). The aneurysm morphology was suitable for WEB implantation. The case was reassessed in the multidisciplinary team and after discussion with the patient, WEB implantation was performed the same day. A 6-F Benchmark catheter (Penumbra, Alameda, California, USA) and a 0.53-mm (0.021 in) Via microcatheter (Microvention, Tustin, California, USA) was used to deploy a single-layer 5-mm (width) × 3-mm (height) WEB single-layer device (C). 5000 IU heparin intravenously was given at the beginning of the procedure and 500 mg aspirin intravenously was given after WEB implantation. Aspirin 75 mg by mouth once daily was given after the procedure for 6 weeks. Complete occlusion of the aneurysm was shown at the end of the procedure with normal filling of the right middle cerebral artery circulation. There were no new complications periprocedurally or during 16 months follow-up. Three and 6 months digital subtraction angiography confirmed persisting complete occlusion (D) (adjacent to the WEB there is en face branch origin, which is not to be confused with a neck remnant).

Table 1. Baseline Patient Characteristics and Preclipping Aneurysm Features.

Patient Number
1 2 3 4 5 6
Age (decade)* 50s 40s 60s 50s 60s 50s
Aneurysm risk factors HTN, smoker HTN, smoker Smoker
Other medical history Chronic obstructive pulmonary disorder Breast cancer
Baseline modified Rankin Scale score 0 0 0 0 0 0
Clinical presentation Mass effect (seizure) Incidental SAH Incidental SAH SAH
Aneurysm localization Left MCA bifurcation Acomm complex Left MCA bifurcation Right MCA bifurcation Right MCA bifurcation Acomm complex
Maximal sac diameter (mm) 21 15 9 8 9 11
Neck width (mm) 5 9 6 6 5 8
Ruptured aneurysm No No Yes No Yes Yes
Thrombosed aneurysm Yes Yes No No No No
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HTN, arterial hypertension; SAH, subarachnoid hemorrhage; Acomm, anterior communicating artery; MCA, middle cerebral artery.

*

Decades given rather than specific age, and individual sex not given, to maintain the highest degree of anonymity. There were 3 female and 3 male patients.

The mean time between unsuccessful surgical intervention and retreatment with WEB implantation was 37 days (range, 2– 90 days) (Table 2). A single WEB singlelayer device was successfully implanted in all cases attempted. Preoperative, intraoperative, and postoperative antiplatelet and anticoagulant therapy was managed in each center in accordance with the local institutional protocol at the time (Supplementary Table 1).

Table 2. Time Between the First Clipping Treatment and Woven Endobridge Implantation Retreatment and pre–Woven Endobridge Implantation Clinical and Aneurysm Features.

Patient Number
1 2 3 4 5 6
Time from clip treatment to Woven Endobridge retreatment (days) 90 2 2 60 60 7
Postclipping modified Rankin Scale score 0 0 1 2 0 0
Maximal sac diameter (mm) 21 15 9 8 4 4
Neck width (mm) 5 9 6 6 4 4
Thrombosed aneurysm Yes Yes No No No No
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There were no periprocedural thromboembolic or hemorrhagic complications (both 0%, 0/6; Table 3). Periprocedural vasospasm was noted without clinical consequence in a single patient. The first and second clinical and radiographic follow-up time points were at 5 months (mean; range 3–6 months) and 15 months (range, 8–24 months) after the procedure, respectively. There was no change in the preprocedural mRS score in all 6 cases periprocedurally and at first and second follow-up time points. In particular, no patient died or became dependent (mRS score 3–6) over the follow-up period. At the second follow-up time point, 3 patients had complete occlusion of the aneurysm (50%, 3/6; WOS score 2), 2 patients had a neck remnant (33%, 2/6; WOS score 3) and I patient a sac remnant (I7%, I/6, WOS score 4). The I patient with a sac remnant had a neck remnant at the first follow-up (3 months), which subsequently became a sac remnant at second follow-up (8 months), at which point the patient underwent further retreatment using coils and an Aneurysm Neck Reconstruction Device (PulseRider [Pulsar Vascular, San Jose, California, USA]) to achieve complete occlusion.

Table 3. Periprocedural Complications and Follow-Up.

Patient Number
1 2 3 4 5 6
Periprocedural complications No No No No No No
Brain ischemia No No No No No No
Hemorrhage No No No No No No
Post–Woven Endobridge immediate modified Rankin Scale score 0 0 1 2 0 0
Aneurysm appearance after device placement Undergoing thrombosis to give complete occlusion (WOS score 2) Undergoing thrombosis to give neck remnant (WOS score 3) Undergoing thrombosis to give neck remnant (WOS score 3) Undergoing thrombosis to give complete occlusion (WOS score 2) Undergoing thrombosis to give neck remnant (WOS score 3) Undergoing thrombosis to give complete occlusion (WOS score 2)
Follow-up modified Rankin Scale score 0 at 6 and 18 months 0 at 6 and 18 months 1 at 3 and 8 months 2 at 6 and 24 months 0 at 6 and 8 months 0 at 3 and 16 months
Follow-up imaging findings Complete occlusion (WOS score 2) at 6 and 18 months MRA Neck remnant (WOS score 3) at 6 and 18 months MRA Neck remnant (WOS score 3) at 3 months DSA and sac remnant (WOS score 4) at 8 months MRA Complete occlusion (WOS score 2) at 6 and 24 months DSA with cone-beam computed tomography angiography (DynaCTA) Neck remnant (WOS score 3) at 6 and 8 months DSA Complete occlusion (WOS score 2) at 3 and 16 months DSA
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WOS, WEB Occlusion Scale; MRA, magnetic resonance angiography; DSA, digital subtraction angiography.

Discussion

Summary of Findings

We showed that WEB implantation was a feasible option in the challenging scenario in which a wide-necked aneurysm or widenecked aneurysmal component requires retreatment after unsuccessful surgical clipping. We observed that there were no complications and high adequate occlusion rates.

Strengths and Weaknesses

To the best of our knowledge, this is the first description of WEB retreatment after unsuccessful surgical clipping.9 Small series case reports such as ours inevitably have inherent limitations and show feasibility only. Our series was retrospective and contained only a few patients. Data from a large prospective study are required to make outcome inferences for this population. However, it is challenging to obtain optimal data, as shown in a recent systematic review of coiling retreatment after clipping in which the mean series size for studies was 8 (range, 3–2I) and all cases were retrospective.9 Furthermore, when stent coiling was assessed specifically, only 5 cases were pooled from 2 series.9 Therefore, given the paucity of data regarding retreatment, our small series is likely to contribute to the interventional neuroradiology literature. A strength of our series is that 4 hospitals contributed cases. Furthermore, all endovascular cases from 6 hospitals with large neurovascular practices were reviewed for inclusion, which represented approximately 35% of United Kingdom practice (the total denominator of endovascular cases was 2 orders of magnitude more than the number of cases included in our series). Therefore, our cases are likely to be reasonably representative of current United Kingdom practice for this uncommon retreatment strategy. Other limitations are that follow-up was relatively short (mean follow-up, 5 months and 15 months) and 3D TOF MRA was used for follow-up in 2 cases. Although a recent meta-analysis has shown that MRA (whether using TOF MRA or contrast-enhanced MRA) is a reliable modality for the follow-up of aneurysms treated using a variety of endovascular techniques (including stent-assisted coiling and flow diverters),23 it is possible that there was a reduction in sensitivity compared with DSA in detecting aneurysmal remnants according to 2 small retrospective studies in which WEB susceptibility was described.24,25 It is conceivable that the adequate occlusion rates observed in our series could be lower. However, in most cases included in the 2 small retrospective studies, first-generation (double-layer) WEBs were used, MRA was performed at a higher field strength (3 T), and a different MRA technique was used, all of which differed from the current series. Furthermore, in our 2 cases, other sequences (T1-weighted and T2-weighted) and scan planes (multiplanar reformat) were reviewed and in all first-treatment WEB implantations, we have yet to discover a false-negative remnant after a subsequent DSA. Also, crosssectional magnetic resonance imaging confirmed occlusion because a decrease in the size of the aneurysm sac on crosssectional imaging seems to be the single most consistent sign of durable aneurysm occlusion (likely implying full endotheli-alization of the device construct and secondary exclusion of the aneurysm from the parent circulation).26,27

Comparison with Studies Worldwide

In our series, no thromboembolic or hemorrhagic complications occurred. As is inherent in small series case reports, statistical comparison cannot be made with other studies. Nonetheless, thromboembolic events (including asymptomatic events) occurred in 14% of patients in the pooled results of 3 multicenter studies (WEBCAST, French Observatory, and WEBCAST-2) investigating WEB for the primary treatment of unruptured aneu-rysms14 and in 8% of patients in a recent meta-analysis of 588 aneurysms (127 ruptured) treated with WEB.16 In a recent series, 16 patients underwent retreatment of recurrent endovascularly treated aneurysms with WEB implantation and there were thromboembolic events in 6%. 13

The morbidity and mortality were 1% and 0%, respectively, in the 3 multicenter studies combined14; 4% and 1%, respectively, in the meta-analysis of 588 aneurysms16; and 6% and 0%, respectively, in the retreatment series.13 In our series, the outcomes were similar (both 0%).

We evaluated aneurysm occlusion with the WOS, which has been used as a measurement scale in 3 large prospective multicenter WEB studies.14 Complete occlusion (WOS score 2), neck remnant (WOS score 3), and aneurysm sac remnant (WOS score 4) at follow-up imaging were observed in 50%, 33%, and 17% of all aneurysms, respectively, at a mean follow-up of 15 months. Because of the small size of our sample, it was not possible to perform statistical analyses of aneurysm factors, such as the influence of the sac or neck size, or surgical factors (incomplete or no clip placed) that might influence occlusion status, but no association seemed apparent. Although reiterating the limitations of comparison with other studies, we observe that the occlusion rates of our series seemed similar to the 3 multicenter studies combined, in which complete occlusion, neck remnant, and sac remnant rates were 53%, 26%, and 21% at 12 months, respectively.14 In the retreatment series, the rates were 33%, 40%, and 27% at 12 months. These occlusion rates also seemed similar to a recent meta-analysis of 588 aneurysms,16 in which the adequate occlusion rate after a median of 7 months follow-up was 84% for unruptured and 85% for ruptured aneurysms, with 83% in our series.

Study Explanations and Relevance from a National and International Perspective

We have shown the feasibility of an additional retreatment strategy after unsuccessful clipping by using WEB implantation. In some scenarios, this strategy may be preferable to clipping, coiling, or the use of stents with or without flow-diverting properties.

Anatomic or technical difficulties are likely to be the cause for unsuccessful clipping at the first treatment, making retreatment with clipping intrinsically un-favorable.28 Furthermore, adhesions surrounding the aneurysm, adjacent tissues, or original clip may complicate retreatment with clipping, particularly when there has been a lengthy interval between the surgeries.1,29The morbidity and mortality are at least 7% (mRS score >2) and 5%, respectively.1,3,10 Intraoperative rupture also seems to be more common during retreatment.10

The same disadvantages relating to coiling, stent-assisted coiling, or flow diversion that led the neurovascular multidisciplinary team to recommend clipping at first treatment persisted when retreatment was discussed. Anatomic characteristics including a high neck/sac ratio, a wide neck, and being located at a bifurcation limited the endovascular options that would typically require temporary balloon assistance as a minimum, or more often a stent (or 2) to avoid coil protrusion into the parent vessel. Procedures using such adjuncts in wide-neck bifurcation aneurysms can be technically complex and, compared with coiling alone, seem to have a higher periprocedural complication rate and a lower adequate occlusion rate, which at 6–18 months may be 63% or lower.30,31 Furthermore, there is an increase in procedural time and radiation dose compared with standard coiling. Two aneurysms were also partially thrombosed (patients 1 and 2); the implication of retreatment with coiling (whether balloon or stent-assisted) is that there may be a higher rate of recanalization than in nonthrombosed cases.32 Flow diversion has been used rarely in bifurcation aneurysms and the long-term effects on covered bifurcation branches and perforating arteries are not yet fully understood.33 There are risks associated with prolonged dual antiplatelet use, which is required after stent-assisted coiling or flow diversion. After subarachnoid hemorrhage, the risk of periprocedural complications associated with dual antiplatelet use is particularly high.34 An additional disadvantage of coiling that occurs after clipping is that treatment seems to be more technically challenging, possibly because perianeurysmal scarring increases the aneurysm wall rigidity.35

When this series was performed, the neurovascular multidisciplinary team had recommended clipping as first treatment, and not WEB implantation, because there were insufficient outcome data for WEB implantation of wide-necked bifurcation aneurysms compared with clipping (patients 1–4) (neither WEBCAST, WEBCAST 2, nor French Observatory studies had been published14 nor had United Kingdom National Institute for Health and Clinical Excellence guidelines been published approving routine first-line use of WEB36). After unsuccessful clipping, because the disadvantages of performing coiling, stent-assisted coiling, or flow diversion persisted and because retreatment with clipping became high risk, a cost-benefit analysis by the neurovascular multidisciplinary team favored WEB implantation as a retreatment strategy. In 2 patients, WEB implantation at first treatment was less suitable because of the aneurysm morphology (patient 5; Figure 3) or entirely unsuitable because of size (patient 6; Figure 4), so this option was never considered by the neurovascular multidisciplinary team initially. However, after clipping, the remodeled aneurysm inadvertently allowed retreatment with WEB implantation.

In the 2 patients in whom there was partially thrombosed aneurysm (patients 1 and 2), the proximal component of the aneurysm was not thrombosed and the size and morphology were suitable for WEB corking of this proximal component (Figure 1).37 At 6 and 18 months, there was adequate occlusion in these 2 aneurysms. Therefore, we have also shown in this series that WEB corking of the proximal component of an aneurysm that is partially thrombosed is a feasible treatment option. The selective targeting of the proximal component does not contradict a report that showed that WEB is a suboptimal treatment for thrombosed aneurysm sacs in general.38

Conclusions

We showed that WEB implantation was a feasible option in the challenging scenario in which a wide-necked aneurysm or widenecked aneurysmal component requires retreatment after unsuccessful surgical clipping. We observed that in our series the implantation was safe (no morbidity and mortality) and effective (high adequate occlusion rates). Technical, radiologic, and clinical outcomes for this indication seem similar to studies in which WEB implantation was used as the primary treatment of aneurysms. We highlight that despite the increasing evidence from prospective studies, not all neurovascular multidisciplinary teams agree that WEB implantation should be used even for first-line treatment.39–41 This is a small series and prospective data from a larger cohort with longer follow-up are optimal to generate higher-level evidence and outcome inferences for this population. If future higher-level evidence shows outcomes to be similar to our observations, potential indications for retreatment with WEB implantation might resemble the indications for retreatment after coil-ing13: 1) bifurcation aneurysm; 2) aneurysm or aneurysmal component after clipping; and 3) configuration suitable for WEB implantation.

Supplementary Material

Supplementary digital content available online.

Citation: World Neurosurg. (2020) 139:111-120. https://doi.org/10.1016/j.wneu.2020.02.101

Journal homepage: www.journals.elsevier.com/world-neurosurgery

Available online: www.sciencedirect.com

Supplementary material

Acknowledgments

This work was supported by the Well-come/Engineering and Physical Sciences Research Council Center for Medical Engineering (WT 203148/Z/16/Z). We thank Mr. Daniel Walsh, Mr. Christos Tolias, and Dr. Jonathan Hart for their support.

Abbreviations and Acronyms

3D

Three-dimensional

DSA

Digital subtraction angiography

MRA

Magnetic resonance angiography

mRS

Modified Rankin Scale

TOF

Time-of-flight

WEB

Woven Endobridge

WOS

WEB Occlusion Scale

Footnotes

CRediT Authorship Contribution Statement

Thomas C. Booth: Conceptualization, Methodology, Investigation, Data curation, Writing -original draft, Writing -review & editing, Visualization, Supervision, Project administration. Carmen Parra-Farinas: Formal analysis, Investigation, Writing -original draft, Writing -review & editing, Visualization. Ruth-Mary deSouza: Formal analysis, Investigation, Writing -original draft, Writing -review & editing. Naga Kandasamy: Resources, Visualization. Jo Bhattacharya: Resources, Visualization. Prem Rangi: Resources, Visualization. Jonathan Downer: Resources, Visualization, Writing -review & editing.

Conflict of interest statement: This work was supported by the Wellcome/Engineering and Physical Sciences Research Council Center for Medical Engineering (WT203148/Z/16/Z).

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