2025 Volume 19 Issue 1 Article ID: tn.2025-0058
Objective: Mirror image aneurysms located in the bilateral distal anterior cerebral arteries (ACAs) present significant technical challenges for both microsurgical and endovascular treatment due to their close proximity. To address these complexities, this technical note aims to describe a stepwise endovascular strategy for treating complex bilateral distal ACA kissing and mirror image aneurysms, highlighting key technical modifications such as preemptive bilateral stent deployment and selective microcatheter angiography.
Case Presentation: A woman in her 60s presented with bilateral distal ACA mirror image aneurysms (right: 10 mm; left: 7 mm). Endovascular treatment was indicated due to their high-risk morphology and a family history of subarachnoid hemorrhage. To overcome anticipated challenges, a stepwise stent-assisted coil embolization strategy was employed. Key steps included preemptive bilateral Neuroform Atlas stent (Stryker, Kalamazoo, MI, USA) deployment validated by cone-beam CT before any coiling, and selective angiography via a microcatheter left in the proximal A2 segment to ensure clear visualization during coil embolization. The procedure was completed without complications, with no recurrence observed at 5-year follow-up.
Conclusion: The stepwise endovascular strategy, which incorporated preemptive bilateral stent deployment prior to any coiling and utilized selective angiography via microcatheter, enabled the safe and effective endovascular treatment of these complex bilateral distal ACA mirror image aneurysms. This technical strategy offers a practical reference for the endovascular management of similarly complex and anatomically constrained aneurysms.
A “kissing aneurysm” refers to a pair of aneurysms that are in contact with each other at their dome while having separate necks, and such lesions are reported to account for less than 1% of all intracranial aneurysms.1,2) “Mirror image aneurysms” are aneurysms that arise symmetrically on corresponding bilateral intracranial arteries and are observed in approximately 2%–12% of all aneurysms.3–5) Distal anterior cerebral artery (ACA) aneurysms represent a relatively rare subset, comprising 3%–7% of all intracranial aneurysms.6,7) Due to the anatomical proximity of the bilateral ACA segments near the midline, aneurysms arising in these locations can occasionally present as either kissing aneurysms or mirror image aneurysms.
Reports of such mirror image or kissing distal ACA aneurysms are limited to isolated case reports or small case series, and most have been managed via microsurgical aneurysm clipping.8–16) Open surgery is often complicated by the narrow interhemispheric fissure, making dissection and confirmation of parent vessels challenging. In contrast, when endovascular coil embolization is selected, various technical challenges may arise, including interference in obtaining optimal working angles, reduced visibility due to adjacent coil masses, and limited catheter maneuverability resulting from the peripheral location of the aneurysms.
Here, we present a rare case of kissing and mirror image aneurysms arising from the bilateral distal ACAs, successfully treated with stent-assisted coil embolization employing a stepwise intraoperative strategy designed to address these technical challenges.
A woman in her 60s with no notable medical history was referred to our institution after bilateral ACA aneurysms were detected during a routine brain checkup MRI (Fig. 1A). Her family history was notable for a son who had experienced subarachnoid hemorrhage (SAH).
CTA revealed 2 aneurysms in close proximity to each other (Fig. 1B and 1C). The distal right ACA aneurysm was irregularly shaped, measuring 10.1 mm in dome diameter, 7.2 mm in height, and 4.3 mm in neck width, and was accompanied by a bleb (Fig. 1D). Similarly, the left-sided aneurysm was also irregular in shape, measuring 7.1 mm in dome diameter, 4.9 mm in height, and 4.4 mm in neck width, and also had a bleb (Fig. 1E). These findings led to the diagnosis of kissing and mirror image aneurysms arising from the bilateral distal ACAs.
DSA revealed hypoplasia of the right A1 segment of the ACA, with both A2 segments visualized via contrast injection from the left internal carotid artery (ICA) (Fig. 2A and 2B). When contrast was injected from the working angle intended to separate the aneurysm necks from their parent arteries, the bilateral aneurysms and ACA branches overlapped, making it difficult to precisely identify the neck morphology (Fig. 2C). Reconstructed images of 3D rotational angiography are shown in Fig. 2D–2G.
Given the family history of SAH and high-risk aneurysm features, the risk of rupture was considered high, and prophylactic treatment was indicated. The wide necks of both aneurysms (right: 4.3 mm; left: 4.4 mm), incorporation of part of the parent vessel into the base of the aneurysms, and the origin of small branches near the aneurysm necks also suggested that simple coiling would be challenging, and that stent assistance would likely be required on both sides for stable occlusion and parent artery/branch preservation. As the aneurysms projected anteriorly from the genu of the corpus callosum, microsurgical clipping was expected to be technically challenging in terms of securing the parent arteries. Furthermore, both aneurysms were embedded within the respective frontal lobes, raising concerns that surgical dissection could result in higher-order cognitive dysfunction. Therefore, stent-assisted coil embolization was selected as the treatment strategy.
Procedure Pre-procedural planning and strategyBased on the preoperative imaging (Fig. 3A), a stepwise stent-assisted coiling strategy was meticulously planned to address several anticipated challenges. This strategy was specifically designed to overcome difficulties unique to kissing and mirror image aneurysms arising from the bilateral distal ACAs, particularly in the context of right A1 segment hypoplasia leading to significant vessel overlap. The key strategic considerations were as follows:
The procedure was performed under local anesthesia. Dual antiplatelet therapy (DAPT) with aspirin (100 mg) and clopidogrel (75 mg) was initiated 2 weeks prior to treatment. Throughout the procedure, activated clotting time (ACT) was maintained above 250 seconds using intravenous heparin. Normotensive blood pressure was maintained.
A 6-Fr FUBUKI guiding sheath (Asahi Intecc, Aichi, Japan) was inserted via the right femoral artery, and a guiding catheter was advanced into the distal left ICA. To minimize the reduction in visibility caused by the coil mass, embolization was initiated with the smaller, left-sided aneurysm. Furthermore, to avoid difficulty in confirming stent deployment after coil placement, both stents were deployed prior to embolization.
Step 1: Preemptive stent deployment in right ACA (aneurysm to be coiled second) (Fig. 3B)
First, a microcatheter (Excelsior XT-17; Stryker, Kalamazoo, MI, USA) was advanced into the right A3 segment of the ACA, and a Neuroform Atlas stent (3.0 × 21 mm; Stryker) was deployed to cover the neck of the right-sided aneurysm.
Step 2: Stent deployment in left ACA (aneurysm to be coiled first) and bilateral stent confirmation (Fig. 3C)
The XT-17 was then guided into the left A3 segment, and another microcatheter (Excelsior SL-10; Stryker) was advanced into the left-sided aneurysm. A 2nd Neuroform Atlas stent (3.0 × 21 mm) was deployed via the XT-17 to cover the neck of the left-sided aneurysm. Then, cone-beam CT using a 20% dilution of contrast medium confirmed adequate stent wall apposition and full expansion of both stents (Fig. 4).
Step 3: Embolization of the left-sided aneurysm with selective angiography (Fig. 3C)
We then embolized the left-sided aneurysm. Because standard left internal carotid angiography visualized the contralateral ACA and aneurysm as well (Fig. 5A), the XT-17 used for stent deployment was retained in the left A2 segment for selective contrast injection (Fig. 5B). Selective angiography of the left ACA enabled clear and precise visualization of the aneurysm neck and its branch vessels, facilitating safe coil embolization without interference from contralateral structures. Five bare platinum coils (Axium Prime; Medtronic, Minneapolis, MN, USA) with a total length of 54 cm were inserted via the SL-10, resulting in complete occlusion of the aneurysm with a modified Raymond–Roy Classification (MRRC)17) of Class I (Fig. 5C and 5D).
Step 4: Embolization of the right-sided aneurysm via trans-cell technique with selective angiography (Fig. 3D)
Next, the SL-10 was advanced into the right ACA and navigated into the right-sided aneurysm through the struts of the already deployed Neuroform Atlas stent (trans-cell technique). As with the left side, contralateral structures were visualized on left internal carotid angiography (Fig. 6A); however, selective angiography from a microcatheter temporarily placed in the right A2 segment allowed clear visualization of the aneurysm neck and branch vessels (Fig. 6B). The coil mass from the previously embolized left-sided aneurysm was smaller in volume than the right-sided aneurysm and caused minimal interference with neck visualization. Ten bare platinum coils (Axium Prime) totaling 99 cm in length were inserted (Fig. 3E), achieving neck remnant occlusion classified as MRRC Class II (Fig. 6C and 6D). Operating time was 172 minutes.
The postoperative course was uneventful, and the patient was discharged home with a modified Rankin Scale score of 0. DAPT was continued for 6 months postoperatively, after which clopidogrel monotherapy was maintained. Antiplatelet therapy was terminated 1 year after the procedure without complications.
Follow-up plain skull X-rays and digital subtraction angiography performed 6 months after the procedure demonstrated stable embolization status, with MRRC Class I occlusion on the left and Class II on the right.
Subsequent follow-up has been conducted every 6 months with brain MRI and plain skull X-rays, and no recurrence has been observed during the 5-year postoperative period.
Distal ACA aneurysms are relatively rare, comprising only 3%–7% of all intracranial aneurysms.6,7) Endovascular coil embolization has been reported to be effective in treating distal ACA aneurysms.18) However, when the aneurysms are small, there is an increased risk of intraoperative rupture. Furthermore, distal locations present additional technical challenges, including small vessel diameter, limited catheter maneuverability, and restrictions on usable devices. Some reports have suggested that surgical clipping offers higher rates of complete occlusion and lower recurrence rates than endovascular treatment in such cases.19) Therefore, treatment strategy must be individualized based on factors such as patient background, aneurysm morphology and location, vascular anatomy, and operator expertise.
Treating bilateral distal ACA kissing and mirror image aneurysms, such as those presented in this case, poses unique challenges, particularly for endovascular approaches.
In our patient, these challenges were amplified by specific anatomical factors. The close proximity of the aneurysms and hypoplasia of the right A1 segment resulted in significant overlap of the aneurysms and parent vessels on working angle views, further obscured by contralateral filling from a single ICA injection. Additionally, the wide necks, irregular shapes with blebs, parent vessel involvement at the base, and adjacent branch origins necessitated stent assistance for secure coil embolization.
Given these specific anatomical constraints and anticipated technical difficulties, we determined that a meticulously planned, stepwise, stent-assisted coiling strategy incorporating preemptive bilateral stent deployment and selective angiography was crucial for achieving safe and effective occlusion of both aneurysms. The key technical aspects of this approach are detailed below.
Preemptive deployment of bilateral stents and confirmation by cone-beam CTThis strategy was considered the most crucial aspect of this treatment due to its role in addressing the unique challenges presented. In conventional stent-assisted coil embolization, a stent is deployed first, followed by confirmation of proper expansion using diluted contrast cone-beam CT before proceeding to coil placement.20) However, in kissing and mirror image aneurysms of the bilateral distal ACA, embolizing 1 aneurysm first can obstruct the field of view for subsequent stent deployment on the contralateral side due to the presence of a coil mass and metal artifacts. To mitigate this, we pre-deployed a stent in the right ACA (to be embolized second), then advanced a microcatheter into the left ACA and deployed the 2nd stent. Bilateral stent deployment was then confirmed with cone-beam CT. This strategy allowed us to avoid visual obstruction and incomplete stent deployment, enabling a safe and systematic treatment. This contrasts with approaches where 1 aneurysm is coiled first, which might have saved a trans-cell technique but would have risked suboptimal stenting of the 2nd aneurysm due to coil shadowing or metal artifact.
Order of aneurysm embolizationIn unruptured multiple aneurysm cases, treatment order should be determined based on rupture risk and technical considerations. In this case, the smaller left-sided aneurysm was treated first. This decision was based on the concern that if the larger right-sided aneurysm were embolized first, the resulting large coil mass might hinder visualization and access to the smaller lesion.
Selective angiography via microcatheter in the ACADue to hypoplasia of the right A1 segment, contrast injection via the left ICA visualized both A2 segments and associated aneurysms, resulting in poor differentiation of aneurysm anatomy. Therefore, the microcatheter used for stent deployment was retained in the A2 segment, and selective angiography was performed through it. This approach minimized interference from contralateral structures and enabled accurate assessment and embolization of the target aneurysm.
On the other hand, the technique used in this case had the following concerns, each of which required consideration:
Considerations for microcatheter management in distal vessels
Leaving a microcatheter, such as the XT-17 (Stryker) used for selective angiography, in a small distal vessel like the A2 segment while another microcatheter is used for coiling does raise theoretical concerns about potential flow stagnation or thromboembolic complications. In this case, the A2 segment was deemed of adequate caliber relative to the microcatheters. Meticulous anticoagulation management with ACT maintained above 250 seconds, along with minimizing the duration of dual catheter presence, were considered crucial to mitigate this risk. No ischemic complications were observed post-procedure.
Rationale and risks of trans-cell technique for the 2nd aneurysm
Our strategy of preemptive bilateral stent deployment necessitated a trans-cell technique for coiling the 2nd (right-sided) aneurysm in distal ACA. Performing a trans-cell technique in a distal vessel inherently carries risks, including potential stent strut deformation, coil herniation, or difficulty with catheter navigation, particularly if visualization is compromised. However, we prioritized secure primary stenting given the wide necks and the risk of coil mass from the 1st aneurysm obscuring the 2nd stent placement. The clear visualization afforded by selective angiography through a microcatheter in the right A2 segment was critical in minimizing the risks associated with trans-cell navigation for the right-sided aneurysm. The Neuroform Atlas stent (Stryker) is also known for its open-cell design, which can be amenable to the trans-cell technique.
Enesi et al. reported 2 cases of coiling for ruptured bilateral ACA aneurysms and suggested the feasibility of endovascular treatment. In their cases, both A1 segments were well-developed, and the aneurysm sizes were not very large, ranging from 4 to 6 mm. They reported successful treatment by embolizing the aneurysms sequentially (1 case was treated on a separate day) without significant issues.15) Schwartz et al. treated bilateral ACA microaneurysms (with rupture on one side) simultaneously. In their case, the aneurysms were small at 1.5 mm in diameter, and thrombus formation occurred in the parent vessel during the procedure, resulting in postoperative lower limb paralysis. It appears that overlapping working angles or visibility problems did not occur due to the very small size of the aneurysms.16)
Our report differs by presenting a stepwise approach with preemptive bilateral stenting specifically designed to overcome poor visualization and ensure stable aneurysm neck coverage prior to any coil introduction in unruptured, wide-necked aneurysms. While individual components like stent-assisted coiling for distal ACA aneurysms or the use of cone-beam CT are established, the novelty of our report lies in the detailed description of an integrated, stepwise strategy tailored to this rare and complex anatomical configuration.
Our case report describes detailed technical strategies for the endovascular management of kissing and mirror image aneurysms in the distal ACA. These strategies may contribute to the development of effective treatment approaches for similarly rare cases. As a technical note on a rare condition, this report focuses on the detailed operative strategy and its rationale rather than providing comparative statistical data. The successful outcome with no recurrence at 5 years in this challenging case underscores the potential efficacy and safety of this tailored approach.
This case report describes a rare presentation of kissing and mirror image aneurysms arising from the bilateral distal ACAs, successfully treated with stent-assisted coil embolization incorporating several technical strategies: preemptive bilateral stent deployment, cone-beam CT evaluation for stent expansion, and selective angiography to optimize visualization.
These approaches may serve as practical reference strategies for the endovascular treatment of complex aneurysms with significant anatomical constraints, such as bilateral distal ACA aneurysms, or in cases involving multiple aneurysms with potentially overlapping working angles.
Although further accumulation and analysis of similar cases are warranted, this report may contribute to expanding the treatment options for such anatomically challenging and rare aneurysmal configurations.
The authors declare that they have no conflicts of interest.
