Cerebral revascularization for the treatment of complex intracranial aneurysms of the posterior circulation: microsurgical anatomy, techniques and outcomes

Efficacy and Safety of Extracranial-Intracranial Bypass Surgery for Posterior Circulation Aneurysms: A Systematic Review and Single-Arm Meta-Analysis

OBJECTIVE

Treating complex posterior circulation aneurysms poses challenges, and extracranial to intracranial (EC-IC) bypass techniques are potential therapeutic options. However, the safety and efficacy of this approach for posterior circulation aneurysms remain unclear. The study's objective was to assess the safety and efficacy of EC-IC bypass in these aneurysms.

METHODS

Adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, we conducted a systematic review on EC-IC revascularization for posterior circulation aneurysms. Included studies had at least 4 patients and reported data on mortality, patency, complications, or clinical outcomes. Favorable clinical outcomes were defined as modified Rankin Scale below 3 or Glasgow Outcome Scale above 3, and complications were any issues related to the bypass procedure.

RESULTS

From 3036 articles reviewed, 22 studies involving 196 patients who underwent 210 EC-IC bypass procedures for posterior circulation aneurysms were selected. The median follow-up period of 14 studies was 31.66 months (6-61 months). Final follow-up indicated a high bypass patency rate of 96% [95% confidence interval [CI]: 91%-100%; I2 = 12%], with a mortality rate of 5% [95% CI: 1%-9%; I2 = 0%]. Additionally, 83% [95% CI: 70%-96%; I2 = 77%] of patients showed good outcomes at the last follow-up. Complications were observed in 40% [95% CI: 26%-55%; I2 = 80%]. Heterogeneity was associated with specific studies.

CONCLUSIONS

EC-IC bypass procedures are a viable treatment option for posterior circulation aneurysms, with high bypass patency rates and favorable clinical outcomes. However, complications, especially neurological deficits, exist. Open revascularization remains essential for neurovascular surgeons dealing with complex aneurysms.

Carotid artery occlusion and revascularization in the management of meningioma

As the carotid artery courses through the skull base and into the subarachnoid space, it lies in close proximity to regions notorious for meningioma growth. Although infrequent, the growth of these tumors can compromise blood flow through the artery, putting the downstream territory at risk for stroke. In other scenarios, removal of these tumors sometimes requires planning to accomplish both tumor removal and revascularization in the same procedure when then the tumor invades the artery. Since revascularization (bypass surgery) is best performed on a nonemergent basis, it should be given consideration in the preoperative setting. Crisis situations related to intraoperative iatrogenic injury are managed methodically by determining the site of vessel injury and then deciding whether a primary repair or bypass procedure is necessary. The mainstays of revascularization procedures of the carotid artery include flow augmentation and flow replacement, with the superficial temporal artery and external carotid artery being the donor sites, respectively. Although tumor control or cure can be accomplished with surgical, radiosurgical, or combined methods, attention to vascular structures and ensuring blood flow preservation as part of the treatment plan is an important tenet in meningioma surgery.

Blood Flow Diversion as a Primary Treatment Method for Ruptured Brain Aneurysms-Concerns, Controversy, and Future Directions

Flow diversion is a novel treatment for brain aneurysms that works by redirecting blood flow away from the aneurysm. Immediately after placement of the stent, blood flow stagnates within the aneurysm dome and it undergoes thrombosis. Over time, a new endothelium develops across the neck, thereby reconstructing the parent vessel and curing the aneurysm. The use of this treatment method for ruptured aneurysms has two specific concerns: 1) risk of hemorrhage from the aneurysm after treatment because of potential delayed aneurysm occlusion; and 2) hemorrhagic complications from antiplatelet use, which is required to prevent thromboembolic complications from the device. In this review, we explore these two concerns based on the emerging published literature. Optimal peri-procedural management of these issues in the neurocritical care setting is vital to improving outcomes. We also identify ongoing clinical trials of flow diversion for the treatment of ruptured aneurysms. Flow diversion is an alternative to clipping or coiling for many ruptured aneurysms and may be potentially more efficacious in certain aneurysm subtypes.

The Superior Cerebellar Artery Aneurysm: A Posterior Circulation Aneurysm with Favorable Microsurgical Outcomes

BACKGROUND

Superior cerebellar artery (SCA) aneurysms are usually grouped with aneurysms that arise from the upper basilar artery or more broadly, the posterior circulation. However, the SCA aneurysm has distinctive anatomy that facilitates safe surgical management, notably few associated perforating arteries, and excellent exposure in the carotid-oculomotor triangle.

OBJECTIVE

To demonstrate the outcomes of patients treated with microsurgery in a continuous surgical series.

METHODS

Sixty-two patients harboring 63 SCA aneurysms were retrospectively reviewed from a prospectively maintained database, focusing on clinical characteristics, surgical techniques, and clinical outcomes.

RESULTS

Of 31 patients (49%) presenting with subarachnoid hemorrhage, the SCA aneurysm was the source in 16 (25%). Thirty-three aneurysms were complex (52%) and 43 patients (59%) had multiple aneurysms. Fifty-seven SCA aneurysms (90.5%) were clipped and 5 were bypassed/trapped or wrapped. Complete angiographic occlusion was achieved in 91.7%. Permanent neurological morbidity occurred in 3 patients and 3 patients that presented in coma after subarachnoid hemorrhage died. All patients with "simple" aneurysms and without subarachnoid hemorrhage had improved or unchanged modified Rankin scale scores. Overall, outcomes were stable or improved in 82.5% of patients.

CONCLUSION

SCA aneurysms are favorable for microsurgical clipping with low rates of permanent morbidity and mortality. Microsurgery should be considered alongside endovascular techniques as a treatment option in many patients.

Meta-analysis of treatment outcomes of posterior circulation non-saccular aneurysms by flow diverters

INTRODUCTION

Non-saccular aneurysms of the posterior circulation are uncommon but highly dangerous lesions. Flow diverter stents have been demonstrated to be effective treatments of various anterior circulation aneurysms, particularly large and giant proximal internal carotid artery aneurysms. However, evidence regarding the treatment of non-saccular posterior circulation aneurysms with flow diverters is lacking.

METHODS

A systematic literature review of the English language literature since 2007 was conducted using PubMed, MEDLINE, and Embase. Keywords and MeSH terms included flow diversion, flow diverter, pipeline, surpass, intracranial aneurysm, vertebrobasilar, and non-saccular. Case reports were excluded. Angiographic and clinical outcomes were pooled using a random effects meta-analysis.

RESULTS

13 retrospective non-comparative studies reporting 129 patients and 131 aneurysm treatments were included. The average number of flow diverters per aneurysm was 4.33. Immediate complete or near complete occlusion of the aneurysm occurred in 25% (95% CI 1% to 60%), and long term occlusion in 52% (29-76%). Periprocedural stroke occurred in 23% of cases. Good long term neurologic outcome (modified Rankin Scale score ≤2) was achieved in 51% (95% CI 31% to 71%). Overall mortality was 21% (95% CI 7% to 38%) and morbidity was 26% (12%-42%). Retreatment was required in 5% (95% CI 0% to 14%). Good neurologic outcome rate was higher in vertebral artery aneurysms (83%) than other locations (18-33%).

CONCLUSIONS

Flow diversion is a feasible and efficacious treatment for non-saccular aneurysms in the posterior circulation. However, the intervention carries a significant risk of periprocedural stroke, and is still associated with high overall mortality. Further studies are needed to identify significant treatment risk factors and optimize patient selection.

A case of endovascular treatment for followed by side to side bypass for vertebral artery dissecting aneurysms involved posterior inferior cerebellar artery

Treatment of complex aneurysms usually entails not only direct clipping but also alternative treatment modality. We recently experienced a case of vertebral artery dissecting aneurysm and obtained good treatment outcomes. Our case suggests that the endovascular segmental occlusion with posterior inferior cerebellar artery (PICA) to PICA side anastomosis might be a good treatment option in patients with complex vertebral artery dissecting aneurysms. A 45-year-old woman has a left vertebral dissecting aneurysm with dizziness. Based on the aneurysmal morphology and the involvement of PICA, the patient underwent side to side anastomosis of the PICA. This was followed by the endovascular segmental coil occlusion. The aneurysmal sac was completely obliterated. At a 2-year follow-up, the patient achieved a good patency of both PICA. In conclusion our case suggests that the endovascular segmental occlusion of the parent artery followed by PICA to PICA bypass surgery through a midline suboccipital approach is a reasonable multimodal treatment option in patients with complex vertebral artery dissecting aneurysms.

Cerebrovascular bypass and aneurysm trapping for the treatment of an A2-segment anterior cerebral artery pseudoaneurysm and herniation through a skull base defect following trauma

Fractures of the anterior skull base can lead to pseudoaneurysm formation as a result of direct injury to a vessel wall. Pseudoaneurysms in this location are challenging to treat, as both perforator and distal blood supply must be maintained. Additionally, traumatic skull base fractures can lead to a rare condition of cerebral blood vessel herniation through the bony defect, further complicating treatment planning. Treatment of these lesions is essential to (1) prevent the occurrence of potentially fatal subarachnoid hemorrhage and (2) prevent dissection from propagating and compromising blood flow to distal vessels, perforators, and even parent vessels. We present a unique case of a traumatic proximal anterior cerebral artery pseudoaneurysm, herniating through a skull base defect. Treatment consisted of aneurysm trapping and bypass with skull base reconstruction.