Low-profile visualized intraluminal support junior-within-enterprise 2 stent technique for a distal middle cerebral artery fusiform aneurysm: A case report

Abstract

Background:

Aneurysms distal to the M2 segment account for 2–7% of middle cerebral artery (MCA) aneurysms. These aneurysms, which are often small and fusiform, have thin walls and are prone to bleeding. Therefore, neck clipping and aneurysmal coil embolization are difficult to perform. Herein, we report a case of distal MCA fusiform thrombosed large aneurysm in which the patient underwent overlapping stent with coil embolization.

Case Description:

A 28-year-old man presented to our hospital due to sudden headache onset. Computed tomography revealed a subarachnoid hemorrhage and oval lesion with calcification in the left sylvian fissure. Digital subtraction angiography revealed an 8-mm fusiform aneurysm in the M2 and M3 segments of the left MCA. We performed palliative coil embolization of the saccular portion of the aneurysm. The patient was discharged 22 days after presentation. Imaging performed 2 months after the initial treatment revealed aneurysm enlargement. Because the patient refused to undergo craniotomy, we performed coil embolization with an overlapping stent. An Enterprise 2 stent was deployed to sufficiently cover the aneurysmal segment. Subsequently, an low-profile visualized intraluminal support junior (LVIS Jr.) stent was placed inside the Enterprise 2 stent, and additional coil embolization was performed. Follow-up imaging 5 months after the second treatment revealed complete resolution of the aneurysm.

Conclusion:

The LVIS Jr.-within-Enterprise 2 stent technique may resolve fusiform aneurysms located in distal arteries and maintain parent artery patency.

INTRODUCTION

Distal middle cerebral artery (MCA) aneurysms are located distal to the M2 segment and account for 2–7% of all MCA aneurysms.[2] Distal MCA aneurysms, which are often small and fusiform, have thin walls and bleed easily. The entire vessel wall of the dilated arterial segment is pathological and lacks a neck, and the lumen may be partially thrombosed and not amenable to conventional treatment techniques.[5] Trapping with bypass, surgical or endovascular trapping only, stent-assisted coil embolization, and flow diverter stent (FDS) placement are possible treatments for distal MCA aneurysms; however, a standard treatment has not been established. This report describes a large thrombosed distal MCA aneurysm that was successfully treated using overlapping stents and coil embolization. To the best of our knowledge, this is the first report of this technique for such a case.

CASE DESCRIPTION

A 28-year-old man presented to our emergency department with sudden headache onset. On arrival, the patient was conscious and exhibited no evidence of neurological deficits. The patient had no relevant medical history. Plain computed tomography revealed a subarachnoid hemorrhage and oval lesion with calcification in the left sylvian fissure [Figure 1a]. Magnetic resonance imaging (MRI) revealed heterogeneous signal intensity, which suggested thrombus formation and calcification within the aneurysmal sac [Figures 1b and c]. Magnetic resonance angiography revealed an aneurysm in the M2 and M3 segments of the left MCA [Figure 1d]. Subsequently, digital subtraction angiography was performed. Left carotid angiography revealed an 8-mm fusiform aneurysm in the M2 and M3 segments of the left MCA [Figures 1e-h]. This aneurysm was considered the source of the hemorrhage; therefore, we performed palliative coil embolization of the saccular portion of the aneurysm to prevent additional rupture [Figures 1i and j]. The patient recovered from surgery without rebleeding, cerebral vasospasm, and hydrocephalus, and he was discharged 22 days after presentation.

Figure 1:

(a) Computed tomography scan showing subarachnoid hemorrhage mainly in the left sylvian fissure and an oval mass lesion with calcification distal to the fissure. (b) Magnetic resonance imaging T1-weighted image shows iso- to low-signal in the lesion. (c) T2-weighted image shows isoto low-signal in the lesion. (d) Magnetic resonance angiography reveals a large aneurysm (arrow) in the M2-3 segment of the left middle cerebral artery. (e) Left carotid angiogram (CAG) showing an aneurysm (arrow) in the M2-3 segment of the left middle cerebral artery. (f and g) 3D-rotational angiography reveals 8 mm sized, fusiform aneurysm with a partially saccular shaped, located on a curved distal middle cerebral artery. (h) Left CAG before coil embolization. (i and j) Left CAG after coil embolization showing that the saccular portion of the aneurysm was obliterated.

At 1 month after the initial treatment, T1 MRI volumetric isotropic turbo spin-echo acquisition (VISTA) revealed that the aneurysm had enlarged from 17 mm to 21 mm [Figures 2a and b]. At 2 months after the initial treatment, T1 MRI VISTA revealed that the aneurysm had increased to 27 mm [Figure 2c]; therefore, we suggested trapping and bypass surgery. However, the patient requested endovascular treatment. Endovascular treatments for distal fusiform aneurysm which can maintain patency of the parent artery are FDS placement and stent-assisted coil embolization. Because FDS is not approved for implantation in peripheral vessels in Japan, stent-assisted coil embolization was selected. Although overlapping of two low-profile visualized intraluminal support (LVIS) stents (MicroVention Terumo, Tustin, CA, USA) is known to enhance the flow diversion effect, concerns arose that the LVIS stent would follow the curvature of the fusiform aneurysm and expand within the aneurysm portion. To address this issue, we first used the Enterprise 2 stent (Codman Neurovascular, Raynham, MA, USA) to straighten the vessel, then inserted the LVIS stent to prevent over-expansion. This approach also has the advantage of preventing kinking of the Enterprise. We decided to perform coil embolization with the LVIS Jr.-within-Enterprise 2 stent. The patient started taking 75 mg of clopidogrel and 100 mg of aspirin daily, and endovascular treatment was performed 2 weeks later.

Figure 2:

Magnetic resonance imaging T1 volumetric isotropic turbo spin echo acquisition. (a) One week after the initial endovascular treatment. The high-intensity area indicated blood flow within the aneurysm, which is 17 mm large (dashed circle). A: Anterior, P: Posterior. (b) One month after the initial treatment, the aneurysm increased 21 mm large (dashed circle). (c) Two months after the initial treatment, the aneurysm increased to 27 mm large (dashed circle).

Under general anesthesia, a 6-Fr FUBUKI guiding sheath (Asahi Intec, Aichi, Japan) was inserted in the left femoral artery and guided to the cervical segment of the left internal carotid artery. Left carotid angiography revealed enlargement of the remnant fusiform aneurysm. A Prowler Select Plus microcatheter (Codman Neurovascular) was guided past the fusiform aneurysm to the distal MCA, and an SL-10 microcatheter (Stryker Neurovascular, Freemont, CA, USA) was inserted in the aneurysm [Figure 3a]. An Enterprise 2 stent (4–30 mm; Codman Neurovascular) was deployed from the distal MCA to straighten it and ensure sufficient coverage of the lesion [Figure 3b]. Thereafter, the Prowler Select Plus microcatheter was advanced through the stented segment into the distal MCA; subsequently, it was replaced with a Headway 17 microcatheter (MicroVention Terumo). Then, an LVIS Jr. stent (3.5 mm–28 mm; MicroVention Terumo) was placed inside the Enterprise 2 stent [Figure 3c]. Subsequently, we performed additional coil embolization within the aneurysm using the jailing technique. The upper component of the aneurysm was embolized, and the procedure was concluded with contrast agent remaining within the newly formed aneurysm [Figures 3d and e]. The LVIS Jr. stent within the Enterprise 2 stent was deployed appropriately and did not overly expand [Figure 3f].

Figure 3:

(a) Left carotid angiography showed that the saccular portion of the aneurysm had been occluded by coil embolization, but the remnant fusiform aneurysm was enlarged. (b) The enterprise 2 stent (4–30 mm; arrow head) was deployed across the fusiform segment as scaffold. (c) The low-profile visualized intraluminal support junior (LVIS Jr.) stent (3.5–28 mm; arrow) was overlaid from the inside of the enterprise 2 stent. (d and e) Additional coil embolization was performed by jailing technique. The final angiogram showed partial inflow of contrast medium into the aneurysm. (f) X-ray showed that the LVIS Jr. stent overlaid inside the enterprise 2 stent was not over expanded and deployed with appropriate size. (g and h) Angiography 2 months after the second treatment showed a shrinkage of the aneurysm and straightening of the parent artery.

Angiography during the 3-month follow-up examination revealed shrinkage of the aneurysm and straightening of the parental artery [Figures 3g and h]. The patient stopped taking clopidogrel after the angiography and continued taking 100 mg of aspirin daily. In addition, a follow-up examination using T1 MRI VISTA revealed aneurysm shrinkage [Figures 4a and b] and complete resolution [Figure 4c] at 3 months and 5 months after the second endovascular treatment, respectively.

Figure 4:

Magnetic resonance imaging T1 volumetric isotropic turbo spin echo acquisition. (a) Two months after the first endovascular treatment and just before the second treatment. The aneurysm was 27 mm large (dashed circle). A: Anterior, P: Posterior. (b) Three months after the second treatment, the high-intensity area shrank (dashed circle). (c) Five months after the second treatment, the high-intensity area disappeared (dashed circle).

DISCUSSION

Although the incidence of intracranial fusiform aneurysms ranges from 3% to 13%, in the distal MCA aneurysm, its rate is as high as 18.8–56.5%.[2,3] Fusiform aneurysms do not have a neck because the entire vessel wall of the dilated arterial segment is pathological, and the lumen may be partially thrombosed.[5] Therefore, simple neck clipping and aneurysmal coil embolization are difficult to perform with radical treatment. Distal MCA aneurysms rarely present with perforating branch occlusion,[2] and surgical or endovascular trapping is often feasible if sufficient collateral blood flow is confirmed. However, trapping with bypass is preferred during direct surgery to maintain the blood flow distal to the aneurysm. Kivipelto et al.[5] reported 24 patients with MCA aneurysms, including nine patients who experienced a distal MCA aneurysm and underwent trapping with bypass, with an aneurysm obliteration rate of 100%. At least, 3 (33%) of those nine patients with a distal MCA aneurysm had postoperative bypass occlusion, and one of those patients experienced worsening symptoms. Immediate and complete aneurysmal occlusion can be achieved with trapping with bypass; however, the increased flow of leptomeningeal collaterals can lead to decreasing flow in the bypass, resulting in delayed bypass occlusion with no or mild neurological symptoms.[5,9] During endovascular treatment, reconstructive techniques such as stent-assisted coil embolization and FDS placement can achieve aneurysmal occlusion and maintain patency of the parental artery. However, during stent-assisted coil embolization, a down-the-barrel view is not always available, and the coil loop cannot avoid overlapping the parent artery. As a result, the surgeon may hesitate during coil packing, and occlusion of the aneurysm is difficult.[4] Therefore, FDS placement may be the most useful procedure during radical treatment of aneurysms. Cimflova et al.[2] reported 23 patients treated with various FDS types for distal MCA aneurysms (13 aneurysms were fusiform, eight were sacculofusiform, and two were saccular); 14 (70%) of 20 patients with available follow-up imaging achieved complete or near-complete occlusion, and stable remodeling was observed in 1 (5%) patient at 12 months. In addition, 2 (8.7%) serious complications, an intraparenchymal hemorrhage around the stent segment 3 days after treatment that required hematoma evacuation and a giant ruptured aneurysm with serpentine transformation and delayed repeat rupture 4 months after treatment, were observed. Other events that resolved without clinical sequelae occurred in 17.4% of patients, including in-stent thrombosis, asymptomatic in-stent stenosis, and FDS deployment failure. Möhlenbruch et al.[8] reported the following results of treatment using the flow re-direction endoluminal device junior stent (MicroVention Terumo) for 42 patients with 47 aneurysms, including 18 MCA aneurysms: 78% (32/41 patients) of aneurysms exhibited complete or near-complete occlusion at 12 months, and the primary safety endpoint (no deaths, no major or minor strokes, and no transient ischemic attacks) was achieved in 93% (39/42 patients) of patients. Side branch occlusion was observed in two patients, and intravenous tirofiban was successfully recanalized in both. The FDS is also associated with high occlusion rates; however, occlusion requires a longer period, and postoperative repeat rupture has been observed. Maintaining patency of the parent artery is an important advantage of the FDS, but it may lead to in-stent thrombosis, stenosis, and side branch occlusion.

Our patient requested endovascular treatment as radical treatment; however, an FDS for distally located aneurysms is not yet available in Japan. Therefore, overlapping stents and coil embolization were used to treat the distal MCA fusiform aneurysm. To the best of our knowledge, this is the first report of this technique for a distal MCA aneurysm. This technique is useful for vertebral artery fusiform and dissecting aneurysms because the method of deploying the LVIS stent within the Enterprise stent is highly effective for diverting flow.[7] The LVIS stent is a braided stent with a high MCR (22–28%) and outward-expanding properties. When placed in a fusiform aneurysm, the stent bulges significantly at the aneurysmal neck (unconstrained segment), thus reducing metal coverage and the flow-diverting effect.[7] In addition, bulging can cause shortening of the proximal or distal side of the stent, resulting in the risk of malposition or delayed stent migration.[1] In contrast, the Enterprise stent, which is a laser-cut stent, has relatively minimal outward expansion. However, the Enterprise stent has a low MCR of approximately 8%, and the flow diversion effect cannot be expected. In the overlapping stent technique, the metal coverage surface area is 36.6% for double LVIS Blue stents and 33.4% for an LVIS Blue-within-an-Enterprise stent. Furthermore, deployment of the LVIS stent within the Enterprise stent allows a scaffold that prevents outward expansion of the LVIS stent at the aneurysm neck, thus maintaining even coverage of the metal surface area.[7]

This treatment may be effective for fusiform aneurysms located in small curved parent arteries, similar to the present case. An in vitro study reported that the Enterprise 2 stent had better wall apposition in curved vessels than that of the Enterprise stent; however, gaps and kinks were still observed in curved vessels with a small radius.[6] We verified the behavior of the Enterprise 2 stent and the LVIS Jr. stent: silicone tubes (inner diameter, 2.0 mm; outer diameter, 3.0 mm) with the same diameter as the normal vascular portion of the present case were used to create a model of a fusiform aneurysm located in a curved vessel (radius of flexion, 10 mm), and their stents the same size were each deployed. The Enterprise 2 stent (4.0–39 mm) deployed alone was not fully expanded in the unconstrained segment, and its diameter was 1.5 mm (white double arrow [Figure 5a]). In contrast, when an LVIS Jr. stent (3.5–28 mm) was deployed alone, it bulged excessively in the unconstrained segment, and the stent cell expanded to 4.0 mm [Figure 5b]. Using the LVIS Jr.-within-Enterprise 2 stent technique, bulging of the LVIS Jr. stent was suppressed, and the Enterprise 2 stent was fully expanded to 2.5 mm [Figure 5c]. An increased MCR is expected to have a flow diversion effect. In the present case, the parent artery was curved, and the Enterprise 2 stent was deployed by un-sheath. In addition, the LVIS Jr. stent was placed within the Enterprise 2 stent to promote straightening, increase MCR, and obliterate the aneurysm. In the case of a tortuous parent artery, the Enterprise 2 stent is prone to kinking. Therefore, care is necessary to avoid pushing the stent when passing through the first stent placed in a straight line.

Figure 5:

In vitro study. The silicone tube has 2.0 mm inner diameter and 3.0 mm outer diameter. Model of a fusiform aneurysm located in a curved vessel (radius of flexion 10 mm). (a) The enterprise 2 stent deployed alone. The stent was not fully deployed in the unconstrained segment and its diameter was 1.5 mm (white double arrow). (b) The low-profile visualized intraluminal support junior (LVIS Jr.) stent deployed alone. In the unbound segment it bulges outwards, opening the stent cell. The diameter was 4.0 mm (white double arrow). (c) The LVIS Jr.-within-Enterprise 2 stent technique. The bulge of the LVIS Jr. stent was suppressed and the enterprise 2 stent was fully expanded. The diameter of the unconstrained segment was 2.5 mm (white double arrows).

CONCLUSION

We report a case of ruptured distal MCA fusiform aneurysm treated for overlapping stent with coil embolization, which resulted in aneurysm obliteration and a good outcome. When using the LVIS Jr.-within-Enterprise 2 stent technique, the Enterprise 2 stent acts as a scaffold to prevent overexpansion and migration of the LVIS Jr. stent. The LVIS Jr. stent has high metal coverage, thus providing high flow diversion. This technique is effective for fusiform aneurysms located in parent arteries with a small radius, such as distal MCA aneurysms.

Ethical approval:

The research/study approved by the Institutional Review Board at Tokushima Red Cross Hospital Ethics Committee, number 462, dated September 01, 2023.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

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