The proximal segment (A1) of the anterior cerebral artery (ACA) is a relatively rare point of origin of aneurysms, consisting of less than 1% of all aneurysms [13]. The A1 segment ranges from the bifurcation of the internal carotid artery (ICA) to the point of the anterior communicating artery. Several treatment options exist, spanning both surgical and endovascular modalities. We present the case of a successful treatment of a lobulated fusiform aneurysm at the right A1/A2 junction treated with a non-overlapping Y-configuration FRED. To our knowledge, this is the first such case reported in the literature.

A 59-year-old female, with a past medical history of migraines, presented after a ground-level fall. She had a past surgical history that included a total knee arthroplasty, hip arthroplasty, and a lumbar discectomy. She had no family history of aneurysms. She reported that she stopped smoking about 4 years prior to the presentation. Physical exam revealed a soft tissue cranial injury. Given the mechanism of injury, head computed tomography (CT) and CT angiography (CTA) were performed. CTA showed an incidental distal right A1 anterior cerebral artery (ACA) aneurysm.

A diagnostic catheter-based cerebral angiogram identified a 7.4 mm lobulated configuration aneurysm at the junction of the right A1/A2 ACA (Figs. 1-5). The patient preferred endovascular options of treatment over observation and conventional clipping. Dual antiplatelet therapy (Aspirin 81 mg and Clopidogrel 75 mg daily) commenced five days prior to the procedure. Her VerifyNow P2y12 was 200 PRU on the day of the procedure.

The procedure was performed under general anesthesia. Seldinger technique access to the right radial artery facilitated the placement of a 7-French sheath. A BMX 81 (Penumbra Inc., Alameda, California) guide catheter was positioned in the right cervical internal carotid artery. A Sofia (Terumo Neuro, Aliso Viejo, California) intermediate guide catheter was used coaxially to place a Headway 21 microcatheter (Terumo Neuro, Aliso Viejo, California) into the distal right A2 accessory ACA.

A Flow Re-direction Endoluminal Device (FRED; Terumo Neuro, Aliso Viejo, California) flow diverter (2.5 mm×25 mm) was implanted into the accessory A2 ACA segment. The Headway 21 microcatheter was then advanced through to the distal right non-accessory A2 anterior cerebral artery segment. A FRED flow diversion device (2.5 mm×30 mm) was implanted across the right A1 and A2 anterior cerebral artery junction, in a non-overlapping Y-configuration (Figs. 6-8).

VasoCT (Philips Healthcare, Best, the Netherlands) demonstrated optimal placement of the first device, with the proximal anchoring aspect positioned within the right A1 ACA segment (Fig. 9). Post-device digital subtraction angiography demonstrated satisfactory stasis within the aneurysm lumen with no localized thromboembolic phenomenon. The twenty-four-hour post-procedure course in the ICU was uneventful. She was discharged home on ticagrelor 90 mg twice daily and Aspirin 81 mg daily. Ticagrelor was selected due to its assured response for platelet inhibition. The concerns for thromboembolic risk prompted the change post-procedure from clopidogrel to ticagrelor.

A brain MRA obtained at six months showed artifact from the devices with occlusion of the aneurysm (Fig. 10). Ticagrelor 90 mg was then changed to 60 mg twice daily, and Aspirin 81 mg was continued. Five days prior to a catheter-based angiogram obtained 10 months post-intervention, ticagrelor was discontinued. The follow-up angiogram demonstrated complete obliteration of the aneurysm (Figs. 11, 12).

This case report details the successful treatment of a complex configuration distal A1 anterior cerebral artery bifurcation aneurysm. The lobulated fusiform aneurysm at the junction of the right A1/A2 ACA demonstrated a single afferent feeder A1 ACA segment with the aneurysm incorporating the A2 ACA efferent parent vessels. Novel placement of non-overlapping Y-configuration FRED flow diverters was used for successful aneurysm closure.

FRED flow diverters used in the case have a unique construct, in that overlapping stents form the basis of flow redirection. For this reason, placement is potentially more predictable. Additionally, resheathing and repositioning with a FRED device can be accomplished with a greater component of the stent already extruded. While there is difficulty in placing a braided flow diverter and the technique entails greater risk, we demonstrate that aneurysm occlusion can be achieved under certain anatomical considerations. The placement of the second device became a viable consideration after successfully placing the first as intended. An Atlas stent with possible coiling through would have been the planned rescue strategy in this case if an unintended overlap occurred.

Novel Y-configuration placement of stents and flow diverters have been used primarily for the treatment of non-sidewall, wide-neck aneurysms. Kissing Y-configuration flow diverter device, as well as overlapping closed cell stent placement, to treat wide neck basilar apex aneurysms with the subsequent addition of intraluminal coils, have been previously described [6,7]. In the instance of the closed cell stent overlap case, delivery of a stent across the right posterior cerebral/basilar artery junction was initially performed. Traversing the already delivered stent, a shorter stent isolated to the left posterior cerebral artery was delivered [6]. In vitro description of Y-configuration placement of a flow diverter though high porosity self-expanding stents as a viable option has been demonstrated with no device-related stenosis [10]. This concept has not been applied in vivo. Overlapping Y-configuration stents placed across a bifurcation aneurysm without coil placement, resulting in aneurysm closure has been documented [5]. Non-overlapping Y-configuration flow diverter placement for successful aneurysm closure has not been previously described. In this case, we hoped to address the problem without intra-aneurysmal catheter placement for coil deposition. We believed the risk of aneurysm perforation was greater due to possible poor visualization of the microcatheter within the aneurysm, given the complex anatomy.

Eight potential Y-configurations of stent placement have been described, concluding that kissing-Y and crossing-Y are the most effective in bench test evaluation to diminish intra-aneurysmal flow velocity, intra-aneurysmal shear stress, and residual wall motion. The non-overlapping Y-configuration is considered the least effective in achieving that goal [4,8]. Aneurysm closure with non-closed cell design Y-configuration stent placement has shown to have higher overall occlusion rates [8]. As a viable intrasaccular flow disruptor, WEB embolization has shown to be safe and efficacious [1]. This device, however, cannot be placed if the efferent branch vessels incorporate the aneurysm lumen, as in our case.

Flow diverter placement to treat wide-neck bifurcation aneurysms fundamentally encompasses compromised patency to the non-engaged bifurcation vessel [3]. A publication detailing placement of a flow diverter across the middle cerebral artery through to the contiguous carotid siphon to treat an A1 anterior cerebral artery aneurysm, as in our case, resulted in complete occlusion of the middle cerebral artery [9]. This technique also entails a high procedural and periprocedural risk rate for major ischemic events [9,11]. Placement of flow diverters in this way compromises perforator vascularity with subsequent ischemic events in 20% of cases in one study [2]. Single flow diverter device placement in this context has also shown a higher propensity for recurrence and an occlusion rate of only 48.1% [14].

Flexible device design is an important consideration in delivery into the diminutive tortuous vasculature. Parent vessel artery remodeling up to a year post-deployment has been shown and is dependent on the type of device [12]. This, in turn, affects occlusion rates [14]. The FRED device design allows for delivery of devices in a non-overlapping Y-configuration technique, consequent to the proximal single-layer anchoring component. This aspect of the design may also be a limiting factor, as it may potentially contribute to persistent aneurysm filling if not satisfactorily placed. This aspect of the design was important in our case to facilitate the delivery of the second device. The self-expanding nature, the high fluoroscopic visualization due to radiopaque markers, and its potential to be repositioned for more precise delivery are additional factors that favor this technique [15]. Excessive manipulation, especially of a longer device, does risk localized vessel injury and thromboembolic risk.

Endovascular treatment for complex configuration aneurysms of the A1 ACA is challenging. Non-overlapping Y-configuration flow diverter placement in an appropriate context may be a viable option. Consideration of this option should be evaluated with each individual patient, accounting for the associated risks and benefits.