A systematic review of non-trunk basilar perforator aneurysms: is it worth chasing the small fish?

Current research status and future of endovascular treatment for basilar artery aneurysms

Aneurysms occurring along the basilar artery (BA) account for <1% of all intracranial aneurysms. Endovascular treatment (EVT) in particular is recommended for large unruptured BA aneurysms and ruptured BA aneurysms. Given that EVT techniques vary, a detailed review of EVT for BA aneurysms is necessary. In this review, the following issues were discussed: the anatomy and anomalies of the BA, the classification of BA aneurysms, the natural history of BA aneurysms, the status of open surgery, the use of EVT for various types of BA aneurysms and the deployment of new devices. According to the findings of this review and based on our experience in treating BA aneurysms, traditional coiling EVT is still the optimal therapy for most BA aneurysms. However, in some BA aneurysms, flow diverter (FD) deployment can be used. In addition, there are also some new devices, such as intrasaccular flow disruptors and stent-like devices that can be used to treat BA aneurysms. In general, EVT can yield good clinical and angiographic outcomes for patients with BA aneurysms. In addition, recent new devices and techniques, such as new-generation FDs generated via surface modification and virtual reality simulation techniques, show promise for EVT for BA aneurysms. These devices and techniques may further improve EVT outcomes for BA aneurysms.

Basilar artery perforator aneurysms: a comparison with non-perforator saccular aneurysms

BACKGROUND

Basilar artery perforator aneurysms (BAPAs) are rare. There is no systematic description of their presentation, imaging, natural history and outcomes and how these compare to conventional non-perforator aneurysms. Thus, the authors in this study aimed to compare BAPAs to non-perforator aneurysms.

METHODS

Cases were identified from a prospective neurovascular database, notes and imaging retrospectively reviewed and compared to a consecutive series of patients with non-perforator aneurysms. Blood volume on CT and vessel wall imaging (VWI) were compared to controls.

RESULTS

9/739 patients with aneurysmal subarachnoid haemorrhage (aSAH) harboured BAPAs. Compared to 103 with aSAH from posterior circulation aneurysms, they were more likely to be male (6/9, p = 0.008), but of equal severity (4/9 poor grade, p = 0.736) and need of CSF drainage (5/9, p = 0.154). Blood volume was similar to controls (30.2 ml vs 26.7 ml, p = 0.716). 6/9 BAPAs were initially missed on CTA. VWI showed thick (2.9 mm ± 2.7) bright enhancement (stalk ratio 1.05 ± 0.12), similar to controls with ruptured aneurysms (0.95 ± 0.23, p = 0.551), and greater than unruptured aneurysms (0.43 ± 0.11, p < 0.001). All were initially managed conservatively. Six thrombosed spontaneously. Three grew and had difficult access with few good endovascular options and were treated through a subtemporal craniotomy without complication. None rebled. At 3 months, all presenting in poor grade were mRS 3-4 and those in good grade mRS 1-2.

CONCLUSIONS

Despite their small size, BAPAs present with similar volume SAH, WFNS grade and hydrocephalus to other aneurysms. They are difficult to identify on CTA but enhance strikingly on VWI. The majority thrombosed. Initial conservative management reserving treatment for growth was associated with no rebleeds or complications.

Ruptured basilar artery perforator aneurysm mimicking superior cerebellar artery aneurysm

BACKGROUND AND IMPORTANCE

The diagnosis of basilar artery perforator aneurysm is difficult due to their small size, with high rates of negative angiography. Furthermore, due to the considerable variation of basilar artery perforator (BAP), even if an aneurysm originates from a BAP, it is often difficult to clearly identify its origin on angiography.

CLINICAL PRESENTATION

A 46-female patient presented with World Federation of Neurological Surgeons Scale 1 subarachnoid hemorrhage. Initial imaging study, including digital subtraction angiography (DSA), revealed no vascular lesions. Two-week after admission, DSA revealed an aneurysm arising from the left superior cerebellar artery (SCA). Endovascular coil embolization was planned first. However, aneurysm selection using microcatheter was failed. Then, surgical approach was done via pre-temporal approach. We identified SCA, but there was no aneurysm. Further dissection revealed an aneurysm arising from basilar artery perforator, which was overlapped by SCA. The parent artery of the aneurysm arose from juxtaproximal to the orifice of left SCA, and crossed SCA at the juxtadistal to the aneurismal sac. Complete clip occlusion was done preserving BAP. After the surgery, the patient developed diplopia without extraoccular movement limitations. Two-month after the surgery, she was fully recovered without any neurologic deficits.

CONCLUSION

It is crucial to adequately consider the possibility of open surgery as a viable option in case that endovascular treatment of aneurysms originated from the distal segment of basilar artery proves unsuccessful.

Micro-guidewire electrocoagulation for the treatment of intracranial aneurysms that are inaccessible by microcatheterization: a case series and review of the literature

BACKGROUND

The use of traditional endovascular techniques for aneurysms that are difficult to catheterize is challenging. We present our experience of using micro-guidewire electrocoagulation for the treatment of aneurysms that were inaccessible by a microcatheter.

METHODS

Seven consecutive patients who underwent endovascular electrocoagulation for the treatment of aneurysms between January 2020 and May 2022 were retrospectively included. Patient demographics, treatment procedures, and follow-up outcomes were assessed. A review of the literature was also performed.

RESULTS

All of the seven treated aneurysms were ruptured, and micro-guidewire electrocoagulation was only conducted if the microcatheter could not advance into the aneurysm or parent artery. After electrocoagulation for 1-4 min, all seven aneurysms disappeared on contrast angiography. Parent artery occlusion was observed in six cases, and post-procedure infarctions of the operating region were identified in three patients. The 3-month follow-up modified Rankin Scale score was 0 in all except one patient. Follow-up angiography was available in six patients, and complete obliteration of the aneurysm was observed in all of them. With a mean follow-up time of 13.6 months, there was no rebleeding in any of the cases. To date, there are only eight published cases of aneurysms treated using micro-guidewire electrocoagulation, and seven of them achieved total occlusion of the aneurysm without neurological deficits.

CONCLUSIONS

Endovascular electrocoagulation is practicable and effective for the treatment of aneurysms that are inaccessible by a microcatheter during short-term observation. Studies on larger populations are needed to further confirm the safety and long-term outcomes for this technique.

Susceptibility weighted imaging for ruptured basilar artery perforator aneurysms in the setting of angiographically negative subarachnoid hemorrhage

BACKGROUND

Ruptured basilar artery perforator aneurysms (BAPAs), defined as microaneurysms which develop in basilar perforator arteries without direct involvement of the basilar trunk, represent a rare cause of subarachnoid hemorrhage (SAH). The diagnosis of BAPAs is difficult because of their small size, with high rates of negative angiography. The development of high-resolution MRI could increase the diagnostic performance. In this study we describe the usefulness of susceptibility weighted imaging (SWI) for the diagnosis of ruptured BAPAs.

METHODS

In a case series, we retrospectively collected data of patients admitted to our institution from 2018 to 2021 for SAH with negative CT angiography who underwent MRI (including SWI) and DSA during hospitalization.

RESULTS

Eight patients with a definitive diagnosis of ruptured BAPA and five patients with a definitive diagnosis of angiogram-negative SAH were included. In all of the patients with BAPAs MRI showed a focal, thick, semi-circumferential SWI hypointensity covering the vessel wall at the level of the BAPA subsequently revealed on DSA; this phenomen is known as 'SWI capping'. No SWI capping was observed in the five patients with a definitive diagnosis of angiogram-negative SAH.

CONCLUSION

SWI capping appears to be a reliable indirect sign for the diagnosis and localization of ruptured BAPAs, a rare form of microaneurysm easily misdiagnosed on DSA in initial angiogram-negative SAH.

Benefit of Advanced 3D DSA and MRI/CT Fusion in Neurovascular Pathology

Digital subtraction angiography provides excellent spatial and temporal resolution; however, it lacks the capability to depict the nonvascular anatomy of the brain and spinal cord.A review of the institutional database identified five patients in whom a new integrated fusion workflow of cross-sectional imaging and 3D rotational angiography (3DRA) provided important diagnostic information and assisted in treatment planning. These included two acutely ruptured brain arteriovenous malformations (AVM), a small superficial brainstem AVM after radiosurgery, a thalamic microaneurysm, and a spine AVM, and fusion was crucial for diagnosis and influenced further treatment.Fusion of 3DRA and cross-sectional imaging may help to gain a deeper understanding of neurovascular diseases. This is advantageous for planning and providing treatment and, most importantly, may harbor the potential to minimize complication rates. Integrating image fusion in the work-up of cerebrovascular diseases is likely to have a major impact on the neurovascular field in the future.

Transpetrosal Approach to a Ruptured Distal Basilar Perforating Artery Aneurysm

Basilar perforating artery aneurysms are rare and underreported vascular anomalies in the cerebrovascular literature. Various open and endovascular treatment approaches can be employed to treat these aneurysms based on several patient- and aneurysm-specific factors. Some authors have even advocated for conservative, nonoperative management. Here, we report a case of a ruptured distal basilar perforating artery aneurysm secured by an open transpetrosal approach. A 67-year-old male presented to our institution with a Hunt-Hess grade 2, modified Fisher grade 3 subarachnoid hemorrhage (SAH). Initial cerebral digital subtraction angiography (DSA) did not identify an intracranial aneurysm or other vascular lesions. However, the patient had a re-rupture event several days after presentation. DSA at this time revealed a posteriorly projecting distal basilar perforating artery aneurysm. Initial attempts with endovascular coil embolization were unsuccessful. Thus, an open transpetrosal approach was taken to gain access to the middle and distal basilar trunk to secure the aneurysm. This case underscores the unpredictability of basilar perforating artery aneurysms and the challenges encountered when considering active treatment. We demonstrate an open surgical approach with an intraoperative video for definitive management after failed attempted endovascular treatment.

A giant basilar artery perforator aneurysm

Basilar artery perforator aneurysms (BAPA's) are a rare entity. Their natural history and treatment are unclear. We describe the largest BAPA reported thus far in literature in a 64-year-old Caucasian woman. This patient did not present with subarachnoid hemorrhage, but with left hemiparesis due to pontine ischemia. The aneurysm was initially misdiagnosed as a tumoral mass in a referring center. Angiography confirmed the presence of a BAPA and a flow diverter was successfully placed. This case shows us that a BAPA can mimic a tumoral mass and can cause ischemia due to mass effect without having ruptured. Both conservative and flow diverter placement seems viable treatment options. Individual patient characteristics and preferences should be considered in decision-making for treatment.

Flow Diverter Treatment of Ruptured Basilar Artery Perforator Aneurysms

Purpose

Ruptured basilar artery perforator aneurysms (BAPAs) represent a very rare cause of subarachnoid hemorrhage and an under-reported subtype of cerebral aneurysm. There is no consensus for the optimal treatment strategy (conservative vs. surgical vs. various endovascular approaches). We aim to present a multicenter experience of BAPA treatment using flow-diverter (FD) stents.

Methods

At five tertiary neurovascular centers, all cases of ruptured BAPAs treated by FD were retrospectively collected. Baseline imaging and clinical characteristics, complications, as well as early and long-term angiographic and clinical outcome (mRS) were analyzed.

Results

Eighteen patients (mean age, 57 years; SD, ±10.7 years) with acute SAH related to a BAPA were treated using 18 FD stents. Aneurysms were detected on initial imaging study in 28%; delayed diagnosis was triggered by clinical deterioration due to rebleeding in 15%. No rebleeding after FD was seen, 28% developed FD-related ischemic complications. At long term (n = 16), overall mortality was 13% (2/16), and favorable outcome (mRS 0–2) was 81% (13/16). All BAPAs (n = 13) were completely occluded at long-term angiographic follow-up.

Conclusion

In our multicenter experience, FD treatment of ruptured BAPAs appears to have comparable safety and efficacy outcomes to FD treatment of other ruptured posterior circulation aneurysms as well as to the conservative management of BAPAs. This treatment strategy for a ruptured BAPA achieved a high rate of angiographic occlusion and favorable clinical outcome; however, as the conservative management also seems to offer similar clinical outcomes an individualized treatment decision is warranted. Future prospective studies comparing both approaches are required.

Supplementary Information

The online version of this article (10.1007/s00062-021-01133-y) contains supplementary material, which is available to authorized users.

Endovascular Therapy for Basilar Arterial Trunk Aneurysms

Background: Although aneurysms rarely occur in the basilar artery (BA) trunk, the majority of those that do are dissection aneurysms. Currently, the mainstream therapy for BA trunk aneurysms is endovascular therapy (EVT), which mainly includes single coiling or conventional low-metal-coverage stent-assisted EVT, but the efficacy remains to be evaluated. Methods: A retrospective study was performed for the patients who were admitted to our institution for BA trunk aneurysms and underwent EVT. A total of 28 patients were collected in this study. Results: The patients were aged 23-71 years (53.7 ± 11.5 years on average); nine were female (32.1%, 9/28), and 19 were male (67.9%, 19/28). The patients were given single coiling or conventional low-metal-coverage stent-assisted EVT. Among the 28 patients, 10 (35.7%, 10/28) developed complications, 90% (9/10) of which were ischemic and 10% (1/10) were hemorrhagic. Among the 28 patients, 5 (17.9%, 5/28) died. The surviving 23 patients (82.1%, 23/28) recovered well. Conclusions: This study found that for BA trunk aneurysms, single coiling or conventional low-metal-coverage stent-assisted EVT still had some risks. The risks are mainly from brainstem ischemia. Therefore, the perforators of the BA trunk must be carefully evaluated and prevented from receiving damage from the EVT procedure. This study also shows that 82.1% of patients recovered well. Therefore, EVT can result in an acceptable prognosis.

Comparison between stenting and conservative management of posterior circulation perforator aneurysms: Systematic review and case series

PURPOSE

Posterior circulation perforator aneurysms (PCPAs) are a rare type of intracranial aneurysms whose natural history and optimal clinical management are still largely unexplored. This study aims to report our experience with treating ruptured PCPAs and to provide a systematic review of the literature to compare the two most established treatment options, endovascular stenting, and conservative management including administration of antifibrinolytic drugs and watchful waiting.

METHODS

We performed a systematic review of the literature following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Major databases were searched for case reports and case report series written in the English language between 1995 and 2020. Additionally, we retrospectively reviewed our stroke center database for cases of ruptured PCPAs between January 2014 and July 2020. Endovascular stenting and conservative treatment were compared using endpoints, including favorable outcome rate (mRS 0-2), occlusion rate, mortality rate, periinterventional complication rate, and re-hemorrhage rate.

RESULTS

We identified 31 patients treated endovascularly using stents and 33 patients treated conservatively, with the administration of antifibrinolytic drugs in 3 of them. Our analysis showed no statistically significant difference between the groups, except for the occlusion rate.

CONCLUSIONS

The optimal management strategy of PCPAs is still unknown, but stenting can be considered as an effective occlusion method with an acceptable complication rate. Preventive ventricular drainage may be necessary due to the high hydrocephalus rate encountered in ruptured PCPAs.

Conservative Management and Natural History of Ruptured Basilar Perforator Artery Aneurysms: Two Cases and Literature Review

BACKGROUND

Basilar perforator aneurysms are rare causes of subarachnoid hemorrhage and their natural history is poorly characterized. Although various treatment strategies have been reported, conservative management is an option that has been associated with a high likelihood of spontaneous resolution.

CASE DESCRIPTION

Here we present 2 cases of subarachnoid hemorrhage, 1 diffuse and the other perimesencephalic, due to small ruptured basilar perforator artery aneurysms. These aneurysms were only identified after repeat angiography. Conservative management with serial imaging was pursued. Both patients did well clinically and repeat imaging demonstrated spontaneous resolution of the ruptured aneurysms. We also provide a literature review of ruptured basilar perforator aneurysms, showing a ~10% re-rupture rate within the early post-rupture period but otherwise a high rate of spontaneous resolution.

CONCLUSIONS

Although basilar perforator aneurysms can re-rupture, there is also a high likelihood of spontaneous resolution. Given the challenges of treatment, conservative management is an option that can be considered.