Treatment of a Ruptured Basilar Artery Perforator Aneurysm in the Subacute Phase Using Overlapping LVIS Blue Stents: A Case Report and Review of the Literature
Authors: Toru Nakai, Tomonori Ichikawa, Masashi Fujimoto, Hiroshi Tanemura, Tomoki Ishigaki, Naoki Toma, Fumitaka Miya
Published: 2026

ABSTRACT
ObjectiveBasilar artery perforator aneurysms (BAPAs) are rare causes of subarachnoid hemorrhage (SAH), and their optimal treatment strategy remains controversial. We report a case of ruptured BAPA successfully treated in the subacute phase with an overlapping stent technique using LVIS Blue stents (Terumo Neuro, Tustin, CA, USA).Case PresentationA 75-year-old woman presented with SAH (Hunt and Hess grade II). Non-contrast head CT demonstrated SAH predominantly in the posterior cranial fossa. Initial DSA performed on the day of onset did not demonstrate a definite aneurysmal lesion; however, subtle focal contrast pooling was observed along the basilar artery (BA) trunk. Repeat DSA performed 4 days later revealed a small saccular dilatation arising from the BA trunk adjacent to a perforating artery. Although initial conservative management was selected, subsequent follow-up angiography demonstrated enlargement of the aneurysmal dilatation. Endovascular treatment with deployment of 2 overlapping LVIS Blue stents was performed on day 16 after onset. The postoperative course was clinically uneventful, with no rebleeding or symptomatic complications; a small asymptomatic diffusion-weighted imaging lesion was noted postoperatively. Follow-up DSA at 1 month demonstrated complete obliteration of the aneurysm.ConclusionThe stent-overlap technique represents a feasible and effective treatment option for ruptured BAPAs. In particular, overlapping stent placement appears to be effective for basilar trunk–related subtypes, in which adequate flow diversion can be achieved while preserving perforator patency.

Introduction

Basilar artery perforator aneurysms (BAPAs) are rare and clinically challenging entities, accounting for less than 1% of all intracranial aneurysms.1–3) However, with advances in imaging techniques and the increasing use of high-resolution angiography, BAPAs are being recognized more frequently, suggesting that these lesions may have been previously underdiagnosed. An optimal treatment strategy should balance the preservation of perforating branches and the parent vessel with sufficient prevention of aneurysmal rupture. Nevertheless, the management of BAPAs remains controversial, with proposed strategies ranging from conservative observation to surgical or endovascular intervention.3,4)

Among the available treatment options, endovascular flow-modifying approaches, including overlapping stent placement and flow-diverting devices, have increasingly been utilized.4) Here, we describe a case of ruptured BAPA successfully treated in the subacute phase using overlapping LVIS Blue stents (Terumo Neuro, Tustin, CA, USA) and review the relevant literature.

Case Presentation

A 75-year-old woman with a medical history of hypertension, dyslipidemia, and type 2 diabetes mellitus was transported to Japanese Red Cross Ise Hospital because of a sudden-onset severe headache. On admission, she was somnolent but exhibited no focal neurological deficits and was graded as Hunt and Hess grade II and World Federation of Neurosurgical Societies grade II. Initial non-contrast head CT revealed subarachnoid hemorrhage predominantly in the posterior cranial fossa (Fig. 1). Initial angiographic evaluation of the basilar artery (BA) on the day of onset did not clearly demonstrate a definite aneurysmal lesion. Although subtle contrast stagnation was suspected along the BA trunk, neither DSA nor 3D-rotational angiography (RA) could clearly delineate an aneurysmal structure, rendering a definitive diagnosis difficult at that time (Fig. 2A and 2B). Accordingly, a strategy of close angiographic surveillance was adopted, with interventional treatment to be considered if deemed necessary.

Non-contrast CT of the head reveals thick subarachnoid hemorrhage predominantly distributed to the posterior cranial fossa and basal cisterns.

(A) DSA of the basilar artery performed on the day of onset shows subtle focal contrast pooling along the basilar artery trunk (arrowhead). (B) 3D-rotational angiography demonstrates the lesion; however, its morphology is not clearly delineated (arrow).

Follow-up angiographic evaluation performed 4 days after onset revealed the emergence of a small aneurysmal change originating from a BA perforator (Fig. 3A). On DSA and 3D-RA, the lesion showed a small saccular configuration with a narrow neck arising from the BA trunk and a dome located adjacent to the origin of a perforating artery. The maximum diameter of the aneurysmal dilatation was approximately 1.6 mm, and the neck width was approximately 1.0 mm. No bleb formation or wall irregularity was identified, and no intimal flap–like findings or luminal irregularity were observed in the BA trunk. Given the limited size of the lesion, an initial strategy of careful observation was continued with the expectation of possible spontaneous thrombosis. Subsequent angiography at 7 days after onset demonstrated persistence of the aneurysmal lesion with a slight decrease in size, indicating neither further progression nor spontaneous regression (Fig. 3B). At 13 days after onset, serial angiographic findings suggested interval growth of the aneurysmal lesion, which had enlarged dorsally and reached a maximum diameter of 2.2 mm, prompting the decision to proceed with endovascular treatment (Fig. 3C). Because the patient was still in the acute phase after aneurysmal rupture, we considered that initiating dual antiplatelet therapy and performing stent-based treatment after the early post-rupture period (within 14 days) would be associated with a lower risk of thrombotic complications. Therefore, endovascular treatment was scheduled on day 16 after onset. During this interval, the patient’s general condition remained stable, and no neurological deterioration was observed. In addition, the procedure was scheduled on day 16 to allow the participation of multiple experienced neuroendovascular specialists to ensure procedural safety. Given that the aneurysm was extremely small and considered unsuitable for coil embolization, and that the use of flow diverters for intracranial aneurysms smaller than 5 mm is not approved in Japan, an overlapping stent technique was selected with the expectation of a flow-diversion effect.

Serial DSA (upper row), corresponding 3D-rotational angiography (middle row), and 3D-rotational angiography–based measurements (lower row) show chronological changes in the ruptured lesion. (A) Follow-up angiography on day 4 after onset demonstrates the development of a small saccular aneurysmal dilatation adjacent to a basilar artery perforating branch, with the aneurysmal neck arising from the basilar artery (arrowhead). (B) Angiography performed on day 7 after onset shows persistence of the aneurysmal dilatation with a slight decrease in size. (C) On day 13 after onset, angiography shows overall enlargement of the aneurysmal dilatation in a dorsal direction (arrowhead), with a maximum diameter of 2.2 mm.

Vessel wall imaging without contrast enhancement was performed before endovascular treatment and showed no high-signal intensity or mural abnormality in either the BA trunk or the aneurysmal wall. Dual antiplatelet therapy was administered as loading doses of aspirin (200 mg) and clopidogrel (300 mg) prior to the endovascular procedure. Preoperative platelet function was evaluated using the platelet aggregatory threshold index method (Sysmex, Kobe, Japan), which demonstrated adequate platelet inhibition (adenosine diphosphate platelet aggregation level [APAL]: 4.8). At our institution, an APAL below 8.0 is considered indicative of sufficient platelet inhibition. For reference, previous studies have reported a correlation between P2Y12 reaction unit (PRU) and APAL, with a PRU value of approximately 240 corresponding to an APAL of 8.2.5)

The procedure was performed under general anesthesia. A 6-Fr, 90-cm FUBUKI guiding sheath (Asahi Intecc, Aichi, Japan) was initially inserted via the femoral artery and advanced into the right vertebral artery. Using a 3.2-Fr/3.4-Fr, 120-cm Tactics catheter (Technocrat Corporation, Aichi, Japan), a Headway 27 microcatheter (Terumo Neuro) was navigated over a 0.014-inch, 215-cm Synchro Select Soft guidewire (Stryker Neurovascular, Fremont, CA, USA) and advanced into the right posterior cerebral artery (P1 segment). The diameter of the BA was measured as 2.8 mm at the distal segment, 3.1 mm at the aneurysm-related segment, and 3.1 mm at the proximal segment. Accordingly, a 3.5-mm-diameter stent was chosen to achieve adequate wall apposition. Two 3.5 × 17-mm LVIS Blue stents were deployed in an overlapping fashion along the BA trunk, covering the aneurysm adjacent to a perforating artery (Fig. 4A). DSA performed after stent placement demonstrated persistent opacification of the aneurysmal dilatation without evidence of contrast stagnation within the aneurysm, indicating the absence of an immediate therapeutic effect (Fig. 4B). Nevertheless, the procedure was concluded in anticipation of a delayed flow-diversion effect.

(A) Cone-beam CT shows 2 overlapping LVIS Blue stents deployed across the aneurysm neck (arrowhead). (B) DSA obtained immediately after placement of the 2 overlapping LVIS Blue stents demonstrates persistent opacification of the aneurysmal dilatation (arrowhead). (C) Follow-up DSA at 1 month after treatment reveals complete obliteration of the aneurysm (arrowhead). (D) Follow-up DSA at 6 months demonstrates persistent complete obliteration of the aneurysm (arrowhead).

LVIS Blue stents, Terumo Neuro, Tustin, CA, USA

Dual antiplatelet therapy with aspirin 100 mg and clopidogrel 75 mg was continued in the postoperative period. Diffusion-weighted imaging performed on the day after the procedure demonstrated a small new ischemic lesion in the right cerebellar hemisphere; however, the patient remained neurologically asymptomatic, and no brainstem infarction was observed. The patient’s postoperative course was stable without rebleeding or new neurological deficits. Follow-up DSA 1 month later demonstrated complete aneurysm obliteration (Fig. 4C). The patient was subsequently transferred to a rehabilitation facility with a modified Rankin Scale (mRS) score of 3. After discharge, follow-up demonstrated improvement of the mRS score to 2 at 6 months after onset. Follow-up DSA performed at 6 months confirmed persistent complete obliteration of the aneurysm without recurrence (Fig. 4D). Dual antiplatelet therapy was subsequently transitioned to single antiplatelet therapy with clopidogrel.

Discussion

BAPAs, first described by Ghogawala and Shumacher in 1996,6) are increasingly recognized as a distinct pathological entity characterized by diagnostic delay and heterogeneous clinical behavior, rather than merely a rare subtype of intracranial aneurysm.3,4,7,8) These aneurysms most commonly arise from paramedian perforators of the basilar trunk, particularly in the mid-basilar segment. Satti et al. proposed a classification system that categorizes these aneurysms into 4 subtypes: Type I, adjacent to a perforating branch; Type II, originating from the perforator base (IIa involving the origin and IIb arising from the dome); and Type III, a fusiform lesion extending beyond the parent vessel1) (Fig. 5). Reported aneurysm sizes are typically very small, often measuring less than 2 mm; therefore, such extremely small aneurysms are frequently not visualized on initial angiographic evaluation. Consequently, delayed visualization on follow-up DSA has been repeatedly reported.3,9) In the present case, the aneurysm was not identified on the initial angiographic study and became evident only on repeat DSA performed 4 days after symptom onset, consistent with previous observations.

Schematic representation of basilar artery perforator aneurysms based on the classification system proposed by Satti et al.1) illustrating their anatomical relationship with the BA trunk and perforating branches. Red shaded areas indicate aneurysmal dilatations. Type I aneurysms arise from the BA trunk adjacent to a perforating artery without direct involvement of the perforator. Type II aneurysms originate from the base of a perforating artery and are further subclassified into Type IIa, in which the aneurysm incorporates the origin of the perforator, and Type IIb, in which the perforating artery arises from the dome of the aneurysm. Type III aneurysms are fusiform in morphology and extend beyond the parent vessel.

BA, basilar artery

Because BAPAs are rare lesions, their natural history and pathogenesis have not yet been fully elucidated. BAPAs may originate from arterial dissection rather than represent true saccular aneurysms, based on their dynamic angiographic changes and their propensity for spontaneous thrombosis, enlargement, or disappearance during follow-up.3) In the present case, although no high-signal intensity was observed on vessel wall imaging, we acknowledge that the absence of contrast enhancement limits the sensitivity for detecting subtle mural pathology, and arterial dissection cannot be completely excluded based solely on these findings. Nevertheless, the short-term morphological changes of the aneurysm on DSA and 3D-RA suggested that the lesion was more likely a localized dissection or pseudoaneurysm rather than a true saccular aneurysm. Given the many unresolved aspects, the optimal treatment strategy for BAPAs remains a subject of ongoing debate. The risk of rebleeding in BAPAs has been reported to be approximately 11%–15%,10) and some authors have advocated aggressive treatment strategies; however, the overall rebleeding rate is generally considered low, which is thought to be attributable to the relatively low hemodynamic stress characteristic of these aneurysms.11) Granja et al. compared patients who underwent active management (including coil embolization, stent placement, surgical clipping, Onyx [Medtronic, Minneapolis, MN, USA] embolization, and flow diversion) with those managed conservatively and reported that favorable functional outcomes (mRS 0–2) were achieved in 86.7% and 79.4% of patients, respectively, thereby demonstrating the utility of conservative management.12) Venegas et al. reported that spontaneous aneurysm occlusion occurred in 80% of patients managed conservatively and that no episodes of rebleeding were observed during the follow-up period, similarly supporting the utility of conservative management.8) Based on these reports, conservative management may be considered as the initial treatment option for BAPAs, as it avoids the inherent risks associated with surgical and/or endovascular interventions. However, spontaneous aneurysm resolution is not always achieved, and in some cases, progressive aneurysm enlargement may be observed. Enomoto et al. reported that endovascular intervention should be considered in such situations.7) In our case, conservative management was initially selected; however, aneurysm regression was not achieved, and instead, progressive enlargement was observed. In such situations, surgical or endovascular intervention may be warranted.

Microsurgical trapping or clipping is technically challenging because of the deep operative field and the substantial risk of perforator injury leading to brainstem infarction. Likewise, coil embolization is often infeasible owing to the extremely small aneurysm size and the absence of a well-defined neck. Consequently, the existing literature suggests that overlapping stent placement or flow diversion within the BA represents a preferred treatment strategy for BAPAs. The stent-in-stent approach aims to increase metal coverage along the vessel wall to attenuate inflow to the aneurysm arising from the perforating artery, facilitating aneurysm thrombosis while preserving perforator patency. The previously reported cases of BAPAs treated with overlapping stent placement that we were able to identify are summarized in Table 1. The literature search was performed using PubMed and Google Scholar, with the keywords “basilar artery perforator aneurysm” and “stent.” Articles published between 2000 and 2025 were screened, and cases describing endovascular treatment of ruptured BAPA with overlapping stent placement were included. In addition, the reference lists of relevant articles were manually reviewed to identify additional eligible cases. Because all aneurysms were small, early detection was often difficult. As a result, the timing of therapeutic intervention varied among cases. Various combinations of stents were used, and additional treatment after initial stent placement was required in 2 cases. Nevertheless, no cases of re-rupture were observed during follow-up. Although the time required to confirm aneurysm disappearance varied among cases, complete aneurysm resolution was ultimately achieved in all patients. The available angiographic images were carefully reviewed, and each case was classified according to the system proposed by Satti et al.1) Although detailed imaging such as 3D-RA would ideally be required and classification was challenging in some cases, all aneurysms except 1 were categorized as basilar trunk–related types (Type I, IIa, or IIb). Only a single case corresponded to the basilar trunk–non-related type (Type III). This distinction is clinically important. In Type III aneurysms, overlapping stents typically cover the perforating artery origin rather than directly covering the aneurysm neck. Because perforating arteries are generally expected to remain patent even when covered by stents and flow-diverting devices, it is questionable whether sufficient flow-diversion effects can be achieved in Type III lesions using overlapping stents. Indeed, previous reports have included very few Type III cases, and the effectiveness of overlapping stent placement for this subtype remains uncertain. In contrast, Type I, IIa, and IIb aneurysms arise in close proximity to the basilar trunk, allowing overlapping stents to directly cover the aneurysm neck while minimizing hemodynamic compromise of the perforating artery. This anatomical relationship may facilitate a more effective flow-diversion effect. In the present case, the aneurysm was classified as Type I, in which flow diversion can be achieved without directly impairing perforator inflow, potentially explaining the favorable treatment response. Further studies are warranted to clarify the efficacy of overlapping stent strategies across different BAPA subtypes. Brainstem perforator territory infarction occurred in 3 of the 12 reported cases (25.0%), 2 of which developed after additional treatment. In the remaining case, the procedure was performed in the acute phase following rupture, and perioperative hypercoagulability may have played a role in the development of the ischemic event. Despite these ischemic events, all patients exhibited only mild neurological deficits and ultimately achieved favorable functional outcomes. Stent overlap for ruptured BAPAs is considered to be relatively safe; however, an initial conservative approach should be prioritized.

Table 1Overview of reported cases of basilar artery perforator aneurysm treated with overlapping stent placementAuthorAge (years old)GenderPresentationAneurysm size (mm)Location (Satti et al.’s classification)1)Used stentsOnset-to-treatment intervalAntiplatelet therapyRebleedingAdditional treatmentTime to aneurysm obliteration after treatmentBrainstem perforator territory infarctionFinal GOS/mRS score at follow-upDeshaies et al. (2011)14)47FHH 32.1 × 2.6I, IIa or IIbEnterprise × 28 daysASA + CLP––6 months–NANyberg et al. (2013)15)40–50MNANAIIa or IIbNeuroform Atlas × 22 monthsASA + CLP––2 months–GOS 560–70FNA2–3IIa or IIbNeuroform Atlas × 22 monthsASA + CLP––2 months–GOS 5Kim and Ko (2014)16)52MHH 22.0 × 2.1IIbNeuroform Atlas + Enterprise18 monthsNA––NA–mRS 0Sahu and Ashpilaya (2017)9)50MWFNS 21.6ILVIS Blue × 23 daysNA––18 months–NAChau et al. (2017)17)53MWFNS 10.5ILeo baby × 22 daysASA + PSG–+ (coil embolization)Immediately after coil embolization+ (after additional coil embolization)mRS 0Satti et al. (2017)1)52MHH 31.8IIaEnterprise × 211 daysASA + CLP–+ (stent placement: Neuroform EZ)1 month after additional stent placement+ (after additional stent placement)mRS 0Buell et al. (2018)18)NANAHH 31.5NALVIS Jr + EnterpriseNANA––NA–mRS 1NANAHH 12.5IIa or IIbNeuroform EZ × 2NANA––4 months–mRS 1Chau et al. (2018)2)59NAWFNS 21.5NALeo baby × 25 daysASA + PSG––6 months–mRS 0Sattur et al. (2020)3)62MHH 2NAIIa or IIbLVIS Jr × 327 daysNA––Immediate–mRS 2Inoue et al. (2020)19)72MNA1.8 × 2.3IIILVIS Blue × 22 daysASA + CLP––3 months+mRS 0Present case75FHH 21.2 × 1.4ILVIS Blue × 216 daysASA + CLP––1 month–mRS 2ASA, acetylsalicylic acid; CLP, clopidogrel; Enterprise, Stryker Neurovascular, Fremont, CA, USA; F, female; GOS, Glasgow Outcome Scale; HH, Hunt and Hess grade; Leo baby, Balt, Montmorency, France; LVIS Blue, Terumo Neuro, Tustin, CA, USA; LVIS Jr, Terumo Neuro; M, male; mRS, modified Rankin Scale; NA, not available; Neuroform Atlas, Stryker Neurovascular; Neuroform EZ, Stryker Neurovascular; PSG, prasugrel; WFNS, World Federation of Neurosurgical Societies grade

Overview of reported cases of basilar artery perforator aneurysm treated with overlapping stent placement

ASA, acetylsalicylic acid; CLP, clopidogrel; Enterprise, Stryker Neurovascular, Fremont, CA, USA; F, female; GOS, Glasgow Outcome Scale; HH, Hunt and Hess grade; Leo baby, Balt, Montmorency, France; LVIS Blue, Terumo Neuro, Tustin, CA, USA; LVIS Jr, Terumo Neuro; M, male; mRS, modified Rankin Scale; NA, not available; Neuroform Atlas, Stryker Neurovascular; Neuroform EZ, Stryker Neurovascular; PSG, prasugrel; WFNS, World Federation of Neurosurgical Societies grade

In the present case, the use of a flow-diverting device was not selected because the use of flow diverters for intracranial aneurysms smaller than 5 mm is not approved in Japan. Although favorable outcomes following flow-diverting device placement for BAPAs have also been reported,13) overlapping stent placement may offer additional flexibility for further endovascular interventions when required. Indeed, previous reports have described successful retreatment with additional overlapping stents or coil embolization after initial stent placement.1,2) In contrast, when a flow-diverting device is used as the initial treatment, subsequent therapeutic options are generally limited. Therefore, overlapping stent placement may represent a reasonable alternative to primary flow diversion in selected cases.

Conclusion

Overlapping stent placement is a feasible treatment option for ruptured BAPAs when conservative management is insufficient. This strategy appears particularly effective for basilar trunk–related subtypes, in which direct coverage of the aneurysm neck allows sufficient flow diversion while preserving perforator patency. In contrast, its efficacy for basilar trunk–non-related subtypes remains uncertain. Further studies are needed to define optimal treatment strategies according to BAPA subtype.