Low-profile visualized intraluminal support Blue stenting within a Neuroform Atlas stent for a large wide-necked aneurysm: A case report and a bench-top experiment

Abstract

Low-profile visualized intraluminal support deployment in an Enterprise has been reported; however, that in an Atlas has yet to be in detail. Enterprise has a closed-cell design, while Atlas has an open-cell design. We detail here a case of a large wide-necked aneurysm treated by coil embolization with low-profile visualized intraluminal support Blue deployment within a Neuroform Atlas and a bench-top experiment using a silicon tube to test low-profile visualized intraluminal support, Atlas, Enterprise, and their combinations. A better low-profile visualized intraluminal support expansion was achieved by simultaneously pushing the wire and the system within the Atlas placed at the aneurysm neck, which resulted in an increased metal coverage of the aneurysm neck and a shorter transition zone with low metal coverage at both ends of the aneurysm neck. This technique may enable a high metal coverage by low-profile visualized intraluminal support expansion without restriction by the Atlas and contribute to aneurysm occlusion by increasing the flow-diverting effect.

Introduction

In the treatment of vertebral artery dissecting aneurysms, good embolization results have been obtained by low-profile visualized intraluminal support (LVIS; Terumo, Tokyo, Japan) deployment within an Enterprise (Codman Neurovascular, Miami Lakes, Florida, USA), with the expectation of increasing the flow-diverting and straightening effects of the parent artery.^1,2 However, detailed reports documenting LVIS deployment within an Atlas (Stryker Neurovascular, Fremont, California, USA) have been scarce. ³

We detail here a case of a large wide-necked internal carotid artery (ICA) aneurysm into which only one microcatheter was guided, and in whom complete occlusion was achieved by coil embolization with LVIS Blue deployment within a Neuroform Atlas. Written informed consent was obtained from the patient for publication of this case report and all accompanying images. In addition, we performed a bench-top experiment to test LVIS, Atlas, Enterprise, and their combinations, simulating the aneurysm neck in the present case.

Case report

A 56-year-old Japanese man with a history of hyperlipidemia developed left hemiparesis while on a business trip abroad and visited a local hospital. Head computed tomography showed intracranial hematoma and subarachnoid hemorrhage. He was hospitalized and received conservative therapy because he preferred to be treated back home. He returned home on the 34th day after onset and visited our hospital. Physical examination revealed a Glasgow Coma Scale score of 14, left hemiparesis, and a modified Rankin Scale score 4. Head computed tomography and magnetic resonance imaging showed subacute hemorrhage from the right sylvian fissure to the subcortical frontoparietal lobe and right ICA aneurysm. He was diagnosed with aneurysm rupture in the subacute phase. Angiography showed a large wide-necked irregular-shaped aneurysm (neck, 5.3 mm; dome, 15.8 mm; and height, 12.4 mm) in the anterior wall of the C1–2 segment of the right ICA (Figure 1(a) and (b)). The ICA size was 3.6 × 2.9 mm in the proximal portion, 3.5 × 4.4 mm at the neck, and 2.6 × 2.3 mm in the distal portion. He was placed on a regimen of aspirin 100 mg/day and clopidogrel 75 mg/day one week before endovascular surgery.

Figure 1.

Imaging findings before, during, and after the first embolization. (a) A working angle of pretreatment right internal carotid artery angiography and (b) three-dimensional rotational angiography show a large wide-necked aneurysm in the anterior wall of the right internal carotid artery at the C1–2 segment. (c) Frontal and (d) lateral views of right common carotid artery angiography show an S-shaped curve at the neck of the right internal carotid artery. (e) A working angle of right internal carotid artery angiography before Neuroform Atlas deployment shows blood flow within the aneurysm. (f) A coiled mass is seen in the native image after Neuroform Atlas deployment. (g) Aneurysm neck remnant in a working angle of right internal carotid artery angiography after the first embolization. (h) A native image after the first embolization shows a coiled mass and a Neuroform Atlas.

Endovascular surgery was performed on the 47th day after onset. Under general anesthesia, we placed an 8-Fr guiding catheter at the right ICA’s cervical portion through the right femoral artery. The right ICA’s cervical portion had an S-shaped curve (Figure 1(c) and (d)) and was difficult to straighten even rotating the neck to the left and right. We tried to insert a 6-Fr Cerulean (Medikit, Tokyo, Japan) and subsequently two microcatheters through the S-shaped curve, but both attempts failed. We were able to insert a 3.4-Fr TACTICS 130 cm (Technocrat, Kasugai, Japan) by using it as a distal access catheter. We then placed an Excelsior SL-10 (Stryker Neurovascular) within the aneurysm, and embolized the aneurysm using a total of 14 coils (210 cm). After embolization, the Excelsior SL-10 and the coils did not stay in the aneurysm due to the wide neck and deviated into the parent artery. Angiography showed aneurysm body filling (Figure 1(e)), and additional coil embolization was required. We deployed a Neuroform Atlas 4.5 × 21 mm from the ICA top to the ICA C2 portion (Figure 1(f)) and embolized the aneurysm with a trans-cell approach and a total of 16 coils (137 cm). Angiography showed aneurysm neck remnant, and we finished the embolization (Figure 1(g) and (h)). The postoperative course was uneventful, with no new neurological deficits. The patient’s modified Rankin Scale score remained at four, and the patient was discharged to a rehabilitation hospital 12 days after surgery.

Six months after surgery, angiography showed coil compaction and aneurysm recanalization (neck, 7.3 mm; dome, 8.7 mm; and height, 8.6 mm). The ICA size was 3.4 × 3.0 mm in the proximal portion, 3.2 × 4.4 mm at the neck, and 3.5 × 3.3 mm in the distal portion. Additional endovascular surgery was performed. Under general anesthesia, we placed an 8-Fr guiding catheter at the ICA’s cervical portion through the right femoral artery. Using a 3.4-Fr TACTICS 130 cm as a distal access catheter, we placed a Headway Duo (Terumo) within the aneurysm via a trans-cell approach. Under the support of a Neuroform Atlas, we embolized the aneurysm using a total of nine coils (98 cm). Angiography showed an aneurysm neck remnant (Figure 2(b)). After removing the Headway Duo, we placed a Headway 21 (Terumo) at the distal M1 segment and deployed an LVIS Blue 4.0 × 22 mm from the proximal M1 segment to the ICA C2 segment, simultaneously pushing the wire and the system to increase the metal coverage at the aneurysm neck (Figure 2(c)–(d)). We completed the surgery after confirming LVIS expansion with high metal coverage at the aneurysm neck and good adhesion to the parent arterial wall by cone-beam computed tomography (Figure 2(e)–(g)). The postoperative course was uneventful, with no new neurological deficits. The patient’s modified Rankin Scale score improved to three, and he was discharged home 5 days after surgery.

Figure 2.

Imaging findings before, during, and after the second embolization. (a) A working angle of right internal carotid artery angiography before the second embolization shows recanalization into the aneurysm. A working angle of right internal carotid artery angiography (b) before and (c) after low-profile visualized intraluminal support (LVIS) Blue deployment shows aneurysm neck remnant. (d) A native image after LVIS Blue deployment shows a coiled mass and an LVIS. (e) A three-dimensional working angle, (f) coronal section, and (g) a three-dimensional angle to visualize the entire LVIS of cone-beam computed tomography using five-times-diluted contrast medium show the LVIS with high metal coverage at the aneurysm neck and good vessel wall adhesion. The bidirectional arrows indicate the transition zones with low metal coverage at both ends of the aneurysm neck. (h) Complete occlusion of the aneurysm is observed at a working angle of right internal carotid artery angiography six months after the second embolization.

Six months after the second surgery, angiography showed complete occlusion of the aneurysm (Figure 2(h)). Clopidogrel was discontinued, and aspirin was continued as follow-up medication.

Bench-top experiment

As a bench-top experiment, we made a rectangular unconstrained segment (7 mm in the long axis) on a silicon tube (3 mm in the inner diameter) to simulate an aneurysm of the neck. An 8-Fr guiding catheter 90 cm was placed 10 cm proximal to the unconstrained segment, from where a Headway 21 was guided across the unconstrained segment, and an LVIS Blue 4.0 × 28 mm was deployed in the unconstrained segment under a stereomicroscope. The metal coverage increased in the center of the unconstrained segment but was low in the transition zones at both ends of the unconstrained segment (Figure 3(a)). When a Neuroform Atlas 4.5 × 30 mm was deployed, the unconnected crown cell protruded into the unconstrained segment (Figure 3(b)). After LVIS deployment within an Atlas by pushing the wire, resistance occurred when pushing the system, and the metal coverage of the unconstrained segment did not increase (Figure 3(c) and (d)). After LVIS deployment within the unconstrained segment of an Atlas by simultaneously pushing the wire and the system, the LVIS protruded into the unconstrained segment, the metal coverage increased, and the lengths of the transition zones were almost the same as those of LVIS deployment alone (Figure 3(e) and (f)).

Figure 3.

A bench-top experiment simulating an aneurysm neck with a silicon tube. The stent is deployed from the left (distal) side to the right (proximal) side. Bidirectional arrows indicate the transition zones with low metal coverage at both ends of the unconstrained segment. (a) In low-profile visualized intraluminal support (LVIS) Blue deployment, the LVIS protrudes into the unconstrained segment with high metal coverage. (b) In Neuroform Atlas deployment, an unconnected crown cell of the Atlas protrudes into the unconstrained segment. In LVIS deployment within an Atlas by (c) pushing the wire first and then (d) pushing the system, the metal coverage of the unconstrained segment did not increase. (e) By simultaneously pushing the wire and the system of an LVIS within an Atlas, (f) the LVIS expanded. After LVIS deployment by (g) pushing the wire first and then (h) pushing the system, the LVIS protruded into the unconstrained segment, and the metal coverage increased. (i) In Enterprise deployment, the Enterprise had almost the same diameter as the lumen of the silicon tube and did not protrude into the unconstrained segment. (j) In LVIS deployment within an Enterprise by simultaneously pushing the wire and the system, the LVIS protruded into the unconstrained segment, the metal coverage increased, the braided wire of the LVIS tilt toward the long axis of the silicon tube (arrows), and the distal transition zones lengthened. In LVIS deployment within an Enterprise by (k) pushing the wire first and then (l) pushing the system, the LVIS protruded into the unconstrained segment, and the metal coverage increased, but the distal transition zones lengthened.

In LVIS deployment alone, the metal coverage of the unconstrained segment increased and the transition zones became shorter by pushing the system after deployment by pushing the wire (Figure 3(g) and (h)). On the other hand, an Enterprise 1 4.5 × 28 mm did not protrude into the unconstrained segment and was deployed with a diameter almost identical to that of the silicon tube’s lumen (Figure 3(i)). In LVIS deployment within an Enterprise, by simultaneously pushing the wire and the system, the LVIS protruded into the unconstrained segment, and the metal coverage increased (Figure 3(j)). However, simultaneously pushing the wire and the system requires a strong force, and the braided wire of the LVIS has a tilt to the long axis of the silicon tube. In comparison with LVIS deployment within an Atlas, LVIS deployment within an Enterprise has a longer distal transition zone and a relatively shorter distance of high metal coverage. After LVIS deployment within an Enterprise by pushing the wire first and then pushing the system with a strong force, the metal coverage of the unconstrained segment increased, but the distal transition zone lengthened (Figure 3(k) and (l)).

Discussion

Atlas has an open-cell design with a cell composed of a concave crown and a convex crown. ⁴ In the bench-top experiment, the braided wire of the LVIS seemed to stick in the convex crown of the Atlas when pushing the system after LVIS deployment (Figure 3(c) and (d)). Simultaneously pushing the wire and the system in the unconstrained segment allowed LVIS deployment with high metal coverage without getting stuck in the convex crown (Figure 3(e) and (f)). In the unconstrained segment, the cells of the Atlas protruded and expanded beyond the diameter of the constrained segment, which may not have hindered LVIS expansion. In the present case, we were able to increase the metal coverage at the aneurysm neck by simultaneously pushing the wire and the system of the LVIS within the Atlas.

Because Enterprise has a closed-cell design with interconnected cells, its stent diameter in the unconstrained segment is almost the same as that in the constrained segment. ¹ To expand an LVIS with a diameter larger than that of the constrained segment, the Enterprise in the unconstrained segment must be expanded. In that case, strong force is required to expand the LVIS in the unconstrained segment, which may have shortened the distance of high metal coverage in the unconstrained segment. Furthermore, the braided wire of the LVIS may tilt to the long axis of the silicon tube due to LVIS expansion restricted by the Enterprise (Figure 3(j)). Therefore, the suitable size of the LVIS deployed in the Enterprise may be almost the same as the vessel diameter of the constrained segment to prevent LVIS protrusion into the unconstrained segment. On the other hand, unlike the Atlas, there is no protruding part in the Enterprise where the braided wire of the LVIS can get caught; therefore, “catch” caused by the Enterprise during LVIS deployment is unlikely to happen.

The metal coverage of the braided stent is generally lower in the transition zones at both ends of the aneurysm neck from the constrained segment of the parent artery to the unconstrained segment of the aneurysm neck.^1,5–7 In both the present case and the bench-top experiment, the metal coverage was lower in the transition zone of LVIS than in the center of the aneurysm neck and unconstrained segment. Because these transition zones may lead to incomplete occlusion of the aneurysm, we performed the densest possible coil embolization under the Atlas support in the present case. Atlas has less metal volume than Enterprise and protrudes into the unconstrained segment. ⁸ Therefore, it is unlikely that LVIS expansion is affected within the Atlas. Since LVIS expansion was not restricted by the Atlas, the transition zone was shortened, which may have led to aneurysm occlusion.

In the present case, LVIS-assisted coil embolization may have resulted in aneurysm occlusion during the first surgery. However, because only one microcatheter was guided into the aneurysm, LVIS-assisted coil embolization with increased metal coverage was difficult to perform. Since coil embolization was inadequate without stent assistance, we deployed a stent that allowed a trans-cell approach. In comparison with Enterprise, Neuroform Atlas is less prone to kinking and flattening in meandering vessels, adheres better to the arterial wall, and maintains the lumen even in small vessels.^9,10 Recent studies have shown that the recanalization rate after embolization is lower with Neuroform Atlas than with Enterprise in stent-assisted coil embolization.^11,12 We therefore deployed a Neuroform Atlas at the initial treatment and performed coil embolization with a trans-cell approach.

Although stent-assisted coil embolization has achieved relatively high aneurysm occlusion efficacy, there are still cases that require retreatment.^3,11,13 In the present case, because the aneurysm neck had enlarged at the time of recurrence, complete occlusion seemed to be difficult to achieve by additional coil embolization alone. We thus deployed an LVIS to increase the flow-diverting effect. Tortuous vessels are prone to LVIS expansion failure ¹⁴ where increasing the metal coverage by pushing the system after LVIS deployment by pushing the wire is necessary. On the basis of the bench-top experiment, pushing the system after LVIS deployment in the Atlas should be performed with caution because the braided wire may be caught in the convex crown.

Conclusion

Simultaneously pushing the wire and the system of an LVIS Blue within a Neuroform Atlas at the aneurysm neck led to a higher metal coverage of the aneurysm neck and a shorter transition zone. This technique may contribute to aneurysm occlusion by increasing the flow-diverting effect and the metal coverage without restriction of expansion by the Atlas.

ORCID iDs

Hiroyuki Ikeda https://orcid.org/0000-0001-5710-7456

Yoshitaka Kurosaki https://orcid.org/0000-0003-0738-760X