2025 Volume 19 Issue 1 Article ID: oa.2025-0043
Objective: Basilar artery perforating aneurysms (BAPAs) represent an infrequent clinical finding, typically manifesting as subarachnoid hemorrhage (SAH). Consensus on the optimal management of this rare entity is lacking. We report a single-center case series of 11 patients diagnosed with BAPAs, providing a detailed description of their clinical presentation, management course, and follow-up.
Methods: A retrospective review of our institutional aneurysm database was performed, encompassing cases treated between January 2008 and 2024. Inclusion criteria required aneurysm localization to the middle or upper 3rd of the basilar artery.
Results: All cases presented with diffuse SAH, with 80% exhibiting a perimesencephalic cisternal bleeding pattern. Notably, in most cases, aneurysms were detected upon repeat angiography, performed approximately 10 days after the initial angiographic study. A conservative management strategy was employed, resulting in spontaneous aneurysm exclusion in 80% of the cohort. No instances of rebleeding were observed during the follow-up period.
Conclusion: Conservative management demonstrated favorable functional outcomes in our case series, marked by a high rate of spontaneous thrombosis. These findings suggest that conservative management is an effective and potentially preferred treatment strategy for this rare pathology, mitigating perioperative risks associated with surgical or endovascular interventions.
Basilar artery perforating aneurysms (BAPAs) are a rare clinical entity with limited coverage in the literature since their initial description by Ghogawala and Shumacher.1) Satti et al. further characterized BAPAs as aneurysms originating from the trunk and/or perforating arteries of the basilar artery, proposing a classification scheme based on their anatomical relationship to the perforator.2) While subarachnoid hemorrhage (SAH) is the predominant clinical presentation, optimal management strategies for BAPAs remain a subject of ongoing debate.
This review aims to present our institutional case series of patients with BAPA-associated SAH, detailing their clinical course and management.
A retrospective review was conducted using the neuroradiological database of patients with ruptured basilar perforating aneurysms managed at our institution between January 2008 and August 2024. Institutional Review Board and Regional Ethics Committee approval was obtained for the study. Inclusion criteria included adult patients (age >18 years) who were exclusively managed conservatively in a critical care unit setting; consequently, none of the included patients underwent surgical clipping or endovascular embolization. Management consisted of close hemodynamic and neurological monitoring, medical management, and oral nimodipine administration for vasospasm prophylaxis initiated upon diagnosis. Patients were continuously monitored for aSAH-associated complications, including vasospasm, hydrocephalus, and rebleeding, through clinical assessment and neuroimaging (CT and/or CTA). Supportive care encompassed pain management, fluid and electrolyte balance maintenance, and other medical needs. Following the period of highest risk for vasospasm, patients were transferred to a lower acuity unit, continuing nimodipine for at least 21 days with ongoing clinical and radiological monitoring.
Data collection included patient demographics, clinical presentation, aneurysm size and location, and clinical and radiological follow-up data. Follow-up assessments were conducted at 10–14 days, 3 months, 6 months, and 1 year after hemorrhage. As per protocol at our center, follow-up assessments were performed at 10–14 days, 3 months, 6 months, and 1 year after hemorrhage. The modality and duration of follow-up were reported for each case, as well as clinical follow-up according to the modified Ranking Scale (mRS), when available. Statistical analysis was performed using STATA 17.0 (STATA LLC, College Station, TX, USA).
We identified 11 patients (8 women) with an average age of 47 years, with 11 perforating aneurysms of the posterior circulation. All the aneurysms were less than or equal to 3 mm, and the average maximum diameter of the aneurysm was 1.3 ± 0.6 mm (range 1.1–1.5 mm). All of them occurred in the middle or upper 3rd of the basilar artery, and all perforating aneurysms were in the proximal portion of the perforating artery (Figs. 1 and 2). All patients presented with diffuse SAH. A diffuse bleeding pattern was seen on CT in 63.6% of the cases, and those involving the perimesencephalic cisterns were seen in 81.8% of the cases (Fig. 3).
In 6 of 11 cases, the aneurysm was detected on the 2nd angiography, which is routinely performed around day 10 after a negative initial study. Follow-up imaging consisted of angiography (81% of patients) and MRA (9%). All ruptured aneurysms were managed conservatively, observing spontaneous exclusion in all controlled cases (9/10) with an average of 100 days after their diagnosis (Fig. 4). In the remaining 1/11 of the BAPAs, their status could not be recorded due to loss of long-term follow-up. Of the patients managed conservatively, 3 (27%) had symptomatic vasospasm, 1 (9%) had hydrocephalus with the need for permanent shunting, and no cases of rebleeding were identified in our series. All conservatively managed patients reached mRS 0 during a follow-up period of 6 ± 3 months. The results of our series are summarized in Table 1.
| Case | Age (years) |
mFisher | WFNS | Pattern of bleeding |
Basilar artery location |
Relation to perforating arteries |
Aneurysm (mm) |
Treatment | Complications | Time to aneurysm disappearance |
Follow-up duration |
Follow-up modality |
Outcome (mRS) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 47 | 3 | 1 | Diffuse + perimesencephalic | Upper | Proximal | 0.8 | Observation | No | <1 month | 12 months | DSA | 0 |
| 2 | 38 | 4 | 1 | Diffuse + perimesencephalic | Upper | Proximal | 1.7 | Observation | Vasospasm | <3 months | 12 months | MRA | 0 |
| 3 | 51 | 2 | 1 | Perimesencephalic | Upper | Proximal | 3.2 | Observation | No | <1 month | 3 months | DSA | 0 |
| 4 | 57 | 4 | 1 | Diffuse + perimesencephalic | Upper | Proximal | 1.1 | Observation | Hydrocephalus | <6 months | 6 months | DSA | 0 |
| 5 | 46 | 4 | 1 | Perimesencephalic | Upper | Proximal | 1.3 | Observation | No | <1 month | 6 months | DSA | 0 |
| 6 | 58 | 3 | 2 | Diffuse | Middle | Proximal | 0.8 | Observation | No | <3 months | 3 months | DSA | * |
| 7 | 47 | 3 | 1 | Diffuse + perimesencephalic | Middle | Proximal | 1.4 | Observation | Vasospasm | * | * | * | * |
| 8 | 42 | 4 | 1 | Diffuse + perimesencephalic | Upper | Proximal | 1.3 | Observation | Vasospasm | Not disappeared | 3 months | DSA | * |
| 9 | 42 | 4 | 1 | Diffuse | Upper | Proximal | 1.5 | Observation | No | >6 months | 12 months | DSA | 0 |
| 10 | 60 | 3 | 1 | Perimesencephalic | Upper | Proximal | 1 | Observation | No | <6 months | 6 months | DSA | 0 |
| 11 | 75 | 3 | 1 | Perimesencephalic | Upper | Proximal | 1.7 | Observation | No | <3 months | 3 months | DSA | 0 |
*Missing data.
BAPA, basilar artery perforator aneurysm; mFisher, modified Fisher grade; mRS, modified Ranking Scale; SAH, subarachnoid hemorrhage; WFNS, the World Federation of Neurosurgical Societies grade
BAPAs are a rare entity, 1st described by Ghogawala and Shumacher, with approximately 56 cases reported in the literature to date.1,3) These aneurysms are often missed on initial angiographic studies. The phenomenon of initially negative angiograms followed by subsequent detection of BAPAs is well documented, with rates of negative initial studies reported to be between 47% and 69% in various series.4–7) Several factors contribute to this diagnostic challenge. First, inherent aneurysm characteristics play a crucial role. BAPAs are typically very small, often with diameters of 3 mm or less,4,6–11) as was observed in our cohort (mean size 1.3 ± 0.6 mm). Their diminutive size makes them inherently difficult to visualize, particularly on initial, potentially less focused, angiographic runs. Furthermore, these aneurysms frequently arise from small-caliber perforator arteries with inherently slower blood flow. Consequently, they may opacify very slowly and typically fill in the late arterial, capillary, or even venous phases of angiography, rather than the robust arterial phase filling seen with larger saccular aneurysms.4,6,8,10–13) Initial angiograms might not be of sufficient duration or include specific attention to these later phases. Partial or complete thrombosis of these small aneurysms, potentially occurring acutely after rupture, can also render them angiographically occult or significantly reduce their apparent size.5,7,9,10,12–14) The thrombus may lyse over time, allowing the aneurysm to become visible on repeat imaging. Additionally, many BAPAs are thought to be dissecting pseudoaneurysms rather than true saccular aneurysms.5,8,12–14) This can lead to atypical morphology, dynamic changes in size or shape, and a propensity for spontaneous thrombosis or recanalization, thereby affecting their visibility at different time points. Second, technical angiographic factors are determinant. Optimal detection necessitates a meticulous angiographic technique, including adequate injection volumes and rates, proper patient immobilization, and careful selection of projections.5,9,11) The use of 3D rotational angiography significantly enhances detection rates compared to 2D DSA by providing superior spatial resolution and allowing for multiplanar reconstructions,10,12) a point we underscore in our study by noting detection on repeat angiography and the importance of 3D rotational angiography. Artifacts from contrast agent washout in the main basilar artery can also obscure the origin of small perforator aneurysms.5) Identification often requires focused attention on the late arterial or capillary phases and may necessitate additional, specific angiographic projections.4,6,13) Finally, the timing of imaging and physiological factors after SAH influence visualization. Angiography performed very early after SAH may be negative due to factors such as arterial vasospasm, common after SAH, which can compress or obscure the small aneurysm or its feeding perforator.6) A localized hematoma or intra-cisternal blood can exert a mass effect, further obscuring a tiny lesion.4) Elevated intracranial pressure (ICP) following SAH might alter hemodynamics in a way that reduces flow into the aneurysm, making it less visible.13) As noted in our series and extensively in the literature,4–7) BAPAs are often detected on repeat angiography, typically performed days to weeks (commonly around 7–10 days) after the initial negative study. This delay may allow for the resolution of acute physiological changes (such as vasospasm or high ICP), lysis of intra-aneurysmal thrombus, or changes in the aneurysm morphology itself. Some BAPAs even exhibit dynamic behavior, including spontaneous regression or transient occlusion,12–14) which could explain their absence on an initial study if imaging is performed during a period of temporary occlusion.
However, subsequent angiographic follow-up, particularly with 3D rotational angiography, significantly increases their detection rate. In fact, studies show that approximately 50% of patients with SAH of unknown origin are found to have previously occult aneurysms on follow-up imaging.2,4) This highlights the critical importance of vigilant surveillance in this patient population. BAPA should be included in the differential diagnosis for patients presenting with diffuse SAH, particularly when the hemorrhage is predominantly located in the posterior fossa and initial noninvasive vascular imaging studies are negative. Definitive diagnosis requires cerebral angiography with digital subtraction, augmented by 3D rotational angiography to comprehensively visualize the intracranial vertebrobasilar circulation.
Due to its rarity, the natural history and pathogenesis of BAPA remain poorly understood. However, its location in non-bifurcation arteries, fusiform morphology, and rapid evolution suggest an association with arterial dissection.5,6) This uncertainty contributes to the ongoing controversy surrounding BAPA management. While some case series advocate for active intervention, either surgical or endovascular, others report successful conservative management. Although the 11%–15% risk of rebleeding associated with untreated aneurysms7–9) often supports arguments for active intervention, this risk appears diminished in BAPA cases. This reduction is likely attributable to the lower hemodynamic stress characteristic of these aneurysms.4) Our findings corroborate this assertion, as no instances of rebleeding were observed among conservatively managed cases in our series.
The inherent technical challenges of accessing and treating BAPA, due to factors such as location, size, and proximity to perforating arteries, coupled with the necessity of dual antiplatelet therapy in the context of stenting, make conservative management a compelling alternative. This is further underscored by the high rate of spontaneous aneurysm exclusion, approaching 70%.10) Our observations are consistent with the existing literature. A systematic review of 56 BAPA cases, encompassing both conservative and active management strategies (coils, stents, clips, Onyx, and flow diverters), demonstrated favorable functional outcomes (mRS 0–2) in 86.7% and 79.4% of patients, respectively.3) These results align with the positive functional outcomes observed in our case series. Given this evidence, we advocate for conservative management as the preferred approach for BAPA, mitigating the inherent risks associated with surgical and/or endovascular interventions.
Following confirmation of a BAPA diagnosis, a conservative management strategy is recommended, with the patient receiving close neurological monitoring in a specialized neurointensive care unit. This approach is warranted given the potential for complications inherent to SAH, including vasospasm and hydrocephalus. Diligent surveillance and proactive management of these complications in a critical care environment can optimize patient outcomes and mitigate the risk of adverse events associated with BAPA.
LimitationsThis study has several limitations. First, it is a retrospective, single-center case series with a limited sample size. Second, the follow-up duration was relatively short. Third, there was a lack of fully standardized imaging and follow-up protocols. Specifically, while DSA, the gold standard for aneurysm evaluation, was used for follow-up in the majority of our patients (81%), MRA was employed in a smaller subset (9%). Given that MRA may have lower sensitivity compared to DSA for detecting very small aneurysms, such as the BAPAs typically found in our cohort (average diameter 1.3 ± 0.6 mm), or for identifying subtle residual aneurysm filling, this variability in imaging modality could introduce a potential for inconsistency in outcome assessment, particularly regarding the confirmation of complete aneurysm exclusion in those few cases followed with MRA. However, the predominant use of DSA for follow-up likely minimizes this potential concern across the entire cohort.
Finally, we acknowledge a key limitation: the absence of a direct comparison group undergoing active BAPA treatment. Although our conservatively managed cohort demonstrated favorable outcomes, including high rates of spontaneous thrombosis and no instances of rebleeding, the study design precludes definitive conclusions regarding the superiority of conservative management over interventional strategies. Consequently, while our findings suggest that conservative management may be a preferred treatment strategy, we recognize that this assertion is based on observational data from a single cohort. Future comparative studies are necessary to definitively ascertain the optimal management approach for BAPAs.
BAPAs are a rare clinical entity, necessitating a high index of suspicion for timely diagnosis. Inclusion of 3D rotational angiography of the intracranial vertebrobasilar circulation is crucial for comprehensive visualization during the diagnostic workup. The observed high rate of spontaneous thrombosis and favorable functional outcomes associated with BAPAs make conservative management an attractive and often preferred treatment strategy. However, further research is needed to confirm these findings and to compare the long-term outcomes of conservative and active management strategies.
The authors declare that they have no conflicts of interest.
