Aneurysms of the Proximal (A1) Segment of the Anterior Cerebral Artery: A Clinical Analysis of 31 Cases

Endovascular management of saccular aneurysms of the proximal A1 segment: technical particularities and long term outcomes

BACKGROUND

Saccular aneurysms of the proximal A1 segment (SAPA1) are rare, but their treatment is challenging and scarcely described in the literature. We report the immediate and long term outcomes of their endovascular management.

METHODS

We retrospectively analyzed all consecutive SAPA1 cases treated endovascularly at our center between 2003 and 2023. Per procedural complications and radioclinical outcomes were prospectively recorded.

RESULTS

Among 2468 patients followed up for aneurysms, 12 (0.49%) had an SAPA1 (average age 53.8±9.6 years, 9 women). The SAPA1 averaged 3.3 mm, all posteriorly oriented. Ten were ruptured (83.3%). Initial treatments included conventional coiling or balloon assisted coiling (CC/BAC) for nine aneurysms, and proximal A1 segment focal occlusion (PA1FO) for three. Initial occlusion was deemed satisfactory in all instances: total occlusion in eight cases (67%) and subtotal occlusion in four cases (33%). Four aneurysmal perforations occurred (33%), all during CC/BAC on ruptured aneurysms. Over a 10.2 year average follow-up, six recanalizations (50%) were noted, all after initial CC/BAC: three were early (≤14 days), with one causing fatal rebleeding. No recanalizations after PA1FO was observed (five in total, two as a complement after CC/BAC). Favorable clinical outcomes (modified Rankin Scale score of 0-2) were seen in 91% of cases (11/12) at the last follow-up.

CONCLUSIONS

Selective coiling of the aneurysmal sac is technically difficult due to their small size and the complex microcatheterization pathway. This method presents a significant risk of aneurysmal perforation, especially in ruptured cases, and a high rate of recanalization. PA1FO, when collateralization permits, appears to be a reliable therapeutic alternative offering favorable long term outcomes.

Study of Typical Ruptured and Unruptured Intracranial Aneurysms Based on Fluid-Structure Interaction

BACKGROUND

Most intracranial aneurysms (IAs) will be abnormal bulges on the walls of intracranial arteries that result from the dynamic interaction of geometric morphology, hemodynamics, and pathophysiology. Hemodynamics plays a key role in the origin, development, and rupture of IAs. In the past, hemodynamic studies of IAs were mostly based on the rigid wall hypothesis of computational fluid dynamics, and the influence of arterial wall deformation was ignored. We used fluid-structure interaction (FSI) to study the features of ruptured aneurysms, because it can solve this problem very well and the simulation will be more realistic.

METHODS

A total of 12 IAs, 8 ruptured and 4 unruptured, at the middle cerebral artery bifurcation were studied using FSI to better identify the characteristics of ruptured IAs. We studied the differences in the hemodynamic parameters, including the flow pattern, wall shear stress (WSS), oscillatory shear index (OSI), and displacement and deformation of the arterial wall.

RESULTS

Ruptured IAs had a larger low WSS area and more complex, concentrated, and unstable flow. Also, the OSI was higher. In addition, the displacement deformation area at the ruptured IA was more concentrated and larger.

CONCLUSIONS

A large aspect ratio; a large height/width ratio; complex, unstable, and concentrated flow patterns with small impact areas; a large low WSS region; large WSS fluctuation, high OSI; and large displacement of the aneurysm dome could be risk factors associated with aneurysm rupture. If similar cases are encountered when simulation is used in the clinic, priority should be given to diagnosis and treatment.

Microneurosurgical management of aneurysms of the A1 segment of the anterior cerebral artery: Anatomy and surgical technique

Background:

Aneurysms of the A1 segment of the anterior cerebral artery (ACA) are rare and have characteristics differentiating them from other intracranial aneurysms. Their microsurgical management is challenging and requires different strategies. In this article, we review the surgical anatomy of the A1 segment of the ACA with cadaveric dissections and describe the microsurgical management of complex A1 aneurysms with illustrative cases.

Methods:

A right pterional craniotomy and Sylvian dissection were performed on a formalin-fixed and silicone-injected cadaver head to depict the key anatomic structures and surgical corridors for microsurgical clipping of A1 segment aneurysms. The microneurosurgical management of ruptured and unruptured aneurysms of the A1 segment of the ACA is described with case illustrations.

Results:

The A1 segment of the ACA can be subdivided into proximal, middle, and distal subsegments, the former having abundant perforating branches. Both patients treated with microsurgical clipping had excellent and durable outcomes and postoperative cerebral angiograms showed complete aneurysm occlusion.

Conclusion:

Small A1 aneurysms may require early treatment as their rupture risk appears to be higher. A1 aneurysms are usually embedded in perforators, especially those arising from the proximal A1 subsegment, and require careful distal to proximal microdissection and strategic placement of the aneurysm clip blades. The approach, arachnoid dissection, and angles of attack are carefully planned after accounting for the aneurysm dome projection, precise location of the aneurysm neck and perforators, and the presence or absence of subarachnoid hemorrhage.

Hemodynamic impact of proximal anterior cerebral artery aneurysm: Mind the posteriorly projecting ones!

Intracranial aneurysm projected posteriorly is associated with high risk of aneurysm rupture. In order to investigate the biomechanical mechanisms for the adverse event, three-dimension intracranial cerebral aneurysms were constructed based on clinical data, and we numerically compared effect of location, position, size, and shape of aneurysm on hemodynamic conditions including velocity, pressure, and wall shear stress (WSS). The numerical results showed that the aneurysm projected posteriorly even at small sizes led to abnormal hemodynamic environment, which was featured by a local high pressure and stress concentration near aneurysm neck area. Moreover, the one located at the proximal A1 segment and ellipsoidal aneurysm would further worse local hemodynamic environment, causing high local stresses. These findings indicated the potential mechanical mechanism for high rupture rate of the aneurysms projected posteriorly, underscoring importance of early and accurate diagnosis and promptly treatment for improved the clinical outcome, even if these aneurysms are of small sizes.

Morphological and Hemodynamic Risk Factors for the Rupture of Proximal Anterior Cerebral Artery Aneurysms (A1 Segment)

Objective

The treatment of unruptured small intracranial aneurysms remains controversial. A distinguishing characteristic of A1 segment aneurysms is that they tend to rupture when they are small, which may be related to their distinctive morphology and hemodynamics. Our study sought to investigate the rupture risk factors of A1 segment aneurysms by analyzing the clinical risk factors, morphology, and hemodynamic characteristics of A1 segment aneurysms.

Methods

We retrospectively enrolled 49 (23 ruptured, 26 unruptured) consecutive patients presenting to our institute with A1 segment aneurysms between January 2010 and March 2020. Independent risk factors associated with the rupture of A1 segment aneurysms were analyzed by multivariate regression analysis in the ruptured group and unruptured group.

Results

Clinical risk factors, including age, sex, hypertension, smoking history, and SAH family history revealed no difference between the ruptured and unruptured groups. The ruptured group presented a significantly larger size (Size, P = 0.007), aspect ratio (AR, P = 0.002), size ratio (SR, P = 0.001), bottleneck index (BN, P = 0.016), dome-to-neck ratio (DN, P = 0.001), and oscillatory shear index (OSI) (P = 0.001) than the unruptured group. The normalized wall shear stress (NWSS) of the ruptured aneurysms was lower than the unruptured group (P = 0.001). In the multivariate regression analysis, only SR (OR = 3.672, P = 0.003) and NWSS (OR = 0.474, P = 0.01) were independent risk factors in the A1 segment aneurysm rupture.

Conclusion

A higher SR and lower NWSS revealed a close connection with the rupture of A1 segment aneurysms in our study, thus providing a reference for clinical decision-making in treating A1 segment unruptured aneurysms.

Endovascular treatment for aneurysms at the A1 segment of the anterior cerebral artery: current difficulties and solutions

Aneurysms located at the A1 segment of the anterior cerebral artery are considered rare and unique entities. Endovascular treatment (EVT) is effective in preventing aneurysmal bleeding. However, EVT for A1 aneurysms is difficult due to their distinctive configurations. A current review of EVT for A1 aneurysms is lacking. Therefore, we focused on the available literature on this specific issue. To more clearly expound this entity, we also provided some illustrative cases. The A1 segment can be equally divided into the proximal, middle, and distal segments. Proximal aneurysms are most common and difficult to treat via EVT. The A1 segment has a complex anatomy and many important branches. Due to the small size, predominant posterior direction, and sharp upturn of the microcatheter from the parent artery, microcatheter positioning and support is difficult for A1 aneurysms. EVT for A1 aneurysms mainly includes reconstructive and deconstructive strategies. The complications of EVT for A1 aneurysms include aneurysmal perforation, thromboembolic events, and coil protrusion related to stent-assisted embolization. A1 aneurysms represent rare and difficult vascular lesions. EVT is quite challenging for A1 aneurysms due to their distinctive configurations. The outcomes are acceptable.

Management of Proximal Segment of the Anterior Cerebral Artery Aneurysms

ABSTRACT

The authors reported 2 cases with proximal anterior cerebral artery (A1) aneurysms, and one was treated with aneurysm clipping, whereas another was treated with coil embolization. The authors suggest both endovascular surgery and aneurysm clipping are good options for A1 aneurysms.

Safety and efficacy of different therapeutic strategies in the endovascular treatment of anterior cerebral artery aneurysms with different features: A single centre experience

BACKGROUND

Outcomes of endovascular treatment of anterior cerebral artery (ACA) aneurysms are still not well-characterized.

OBJECTIVE

The study aimed to review the clinical effect, procedure-related complications and follow-up outcomes and to evaluate the safety and efficacy of endovascular treatment of ACA aneurysms in our center experience.

METHODS

From August 2014 to August 2018, a total of 75 consecutive patients with 77 ACA aneurysms were treated via the endovascular approach after providing informed consent. A retrospective review of the clinical, radiological, and endovascular details of these patients was conducted.

RESULTS

The mortality and the morbidity in this study were 4% and 9.3%, respectively. Compared with A1 and A2 aneurysms, intraoperative rupture was more common in A3 aneurysms (P = 0.029). Difference between the ruptured and unruptured aneurysms in the distribution of therapeutic strategy (P = 0.003) and immediate embolization degree (P = 0.004) was also significant. Statistical analysis demonstrated that the larger aneurysm (P = 0.031) was, the greater the ratio of aneurysm size to parent artery diameter (P = 0.029) was, the more likely the unruptured aneurysms were to occur ischemic events. Higher Hunt-Hess grade (P = 0.0066) was an independent risk factor for poor clinical outcome.

CONCLUSION

Endovascular treatment is feasible and effective for ACA aneurysms.

Endovascular Treatment of Ruptured Proximal Segment of the Anterior Cerebral Artery Aneurysms: Single-Center Experience and Literature Review

BACKGROUND

Proximal anterior cerebral artery (A1) aneurysms are rare among all intracranial aneurysms and are regarded as difficult to treat endovascularly. Treatment is even more challenging in patients with ruptured aneurysms and acute subarachnoid hemorrhage owing to the small size and proximity to perforators. Though challenging, endovascular treatment can provide favorable outcomes in such patients. We report our case series of endovascular treatment in ruptured proximal A1 aneurysms.

METHODS

Between January 2010 and December 2017, 1200 aneurysms were treated endovascularly at our center. There were 15 patients with 15 ruptured proximal A1 aneurysms who presented with subarachnoid hemorrhage. Five patients underwent simple coiling, 9 underwent balloon-assisted coiling, and 1 underwent catheter protective coiling. Medical records and angiographic results were obtained retrospectively.

RESULTS

All aneurysms were successfully treated with endovascular techniques. Multiplicity rate was 53.3% (n = 8). Initial complete obliteration rate was 93.3% (n = 14), with a 13.3% recurrence rate (n = 2). One patient experienced intraoperative bleeding; this was the only procedure-related complication. Eleven patients (73.3%) had a good clinical outcome. When excluding Hunt and Hess grade 4 patients, the good outcome rate was 81.8%.

CONCLUSIONS

Ruptured proximal A1 aneurysm is a rare condition and is highly associated with multiple aneurysms. Despite being a more difficult and complicated technique, endovascular coiling performed in high-volume, experienced medical centers is an effective modality with excellent clinical outcomes.