Modern Paradigms for the Treatment of Ruptured Anterior Communicating Artery Aneurysms (2015)

The anterior communicating artery (ACoA) is a common location for both ruptured and unruptured aneurysms. As with the treatment of all intracranial aneurysms, microsurgical clip occlusion has long represented the traditional and time-tested method of treatment. However, with the evolution of endovascular technology and improvements in catheter design that allowed easier access to the ACoA complex, coiling for lesions in this location became safer, with early series demonstrating good results.1 As a result, ACoA aneurysms are commonly treated by both modalities, although modern paradigms vary from institution to institution. In addition, questions remain regarding the optimal treatment strategies of complex lesions of this location, especially given that no modern prospective studies of ACoA outcomes have been completed to date. Ruptured ACoA aneurysms often demonstrate complex morphological features such as variable dome angle projection, involvement of branch and daughter (A2) vessels, and proximity to critical perforators. Classic indications for clipping often include variables such as dome-to-neck ratio, complex branch vessel morphology, surgical hematomas, and lesions too small to coil (Figure 1). Other variables commonly associated with a propensity for clipping over coiling include multiple anterior circulation aneurysms, young patient age, and large or giant aneurysms. Multiple aneurysms are also often approached with microsurgical clipping, especially those with an unclear hemorrhage pattern, to explore or treat multiple lesions with a single surgical approach (Figure 2). Aneurysms in young patients and large or giant lesions are often clipped because of the higher likelihood of recurrence and potential retreatment, although these indications have yet to be evaluated in a clinical trial setting.FIGURE 1: Coronal section of computed tomographic angiogram demonstrating a ruptured anterior communicating artery aneurysm with large intraparenchymal hematoma requiring surgical evacuation. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.FIGURE 2: Digital subtraction angiography. Right internal carotid injection demonstrating multiple anterior circulation aneurysms with an unclear source of subarachnoid hemorrhage. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.Additionally, aneurysmal dome projection has been cited as a potentially viable driver of the treatment paradigm. Posterior dome projection has been reported as a significant risk factor for ischemic complications after microsurgical clipping, as well as for recanalization after coiling.2,3 Another study from the past decade found that lesions with an anterior projection were more likely to be associated with technical success when coil embolization was attempted, whereas inferiorly projecting and wide-necked aneurysms had a significantly higher rate of recanalization.4 Moreover, advances in techniques and technology have allowed the treatment of more complex ACoA lesions, including balloon remodeling. Although early series suggested unacceptably high rates of thromboembolic complications with balloon remodeling, the Analysis of Treatment by Endovascular Approach of Non-ruptured Aneurysms (ATENA) trial and the Clinical and Anatomic Results in the Treatment of Ruptured Intracranial Aneurysms (CLARITY) trial have shown balloon-assisted coiling to be safe and effective for both ruptured and unruptured aneurysms.5-9 We recently described our technical considerations and nuances for balloon remodeling of ACoA lesions and have shown that with the use of such techniques as bilateral femoral artery access, crossing balloons, and variable balloon trajectories, morphologically complex lesions can be treated safely and effectively.10 With sufficient training and application to appropriate indications, these techniques have allowed the treatment of lesions previously thought to be unsuitable for endovascular modalities. There have been 2 major prospective randomized trials in the treatment of ruptured intracranial aneurysms: the Barrow Ruptured Aneurysm Trial (BRAT)11 and the International Subarachnoid Aneurysm Trial (ISAT)12 (Table). Although ISAT demonstrated lower rates of death or disability at 1 year for the coiling group, BRAT did not find any significant differences between the 2 groups. There were several differences in trial design, but perhaps none more important than the question of equipoise for included patients. In ISAT, inclusion was limited solely to lesions determined in a subjective manner by individual practitioners to demonstrate purported clinical equipoise. In BRAT, this was avoided by prerandomization of all patients with aneurysmal subarachnoid hemorrhage during the trial period, although the impact of lesions deemed unsuitable for coiling and subsequently crossed over to clipping has been debated.13,14 These differences underscore not only the difficulty of surgical trial design but also the difficulty in interpreting trial results for the improvement of clinical practice and patient care.TABLE: Comparison of General Characteristics of the International Subarachnoid Aneurysm Trial (ISAT) and the Barrow Ruptured Aneurysm Trial (BRAT)aPreliminary subset analyses of ACoA patients from BRAT were recently completed and presented.15 Clinical outcomes between clipping and coiling at discharge and at the 1- and 3-year follow-up were the same in both the as-treated and intention-to-treat analyses. Rates of complications and retreatment also did not differ between the 2 groups. With these parameters, we were able to better characterize a modern paradigm for the management of ruptured ACoA aneurysms based on the results of a high-quality prospective randomized trial. Since BRAT ended in 2007, our practice has continued to evolve, and our crossover rate has decreased. Although nearly all ACoA lesions at our institution are now approached with a balloon in place, this was not our practice during the BRAT study period because rates of thromboembolic events during balloon-assisted coiling were thought to be unacceptably high. Many lesions that crossed over to the clipping group in BRAT could thus be approached with balloon-assisted coiling in the present day (Figure 3). Recent developments in detachable coil technology have also made possible the safe treatment of small saccular aneurysms16,17 (Figure 4). Small lesions ultimately crossed over in BRAT may very well have been candidates for treatment with today's coil technology. Thus, clinical trials are often a snapshot in time because endovascular technology continues to evolve as a “moving target” in outcome studies. Although some ACoA aneurysms in BRAT had morphological characteristics deemed unsuitable for coiling at the time of treatment, advances in techniques and technology have brought coiling to a point of equipoise with microsurgical clipping because the majority of lesions are amenable to both modalities in experienced hands.FIGURE 3: A and B, digital subtraction angiography. Internal carotid artery injections demonstrating examples of anterior communicating artery aneurysms with wide necks crossed over to clip occlusion in the Barrow Ruptured Aneurysm Trial. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.FIGURE 4: Digital subtraction angiography. Internal carotid artery injection demonstrating a small anterior communicating artery aneurysm deemed too small for coil embolization in the Barrow Ruptured Aneurysm Trial and crossed over to clip occlusion. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.Ultimately, large-scale clinical trials evaluating microsurgical clip occlusion vs coil embolization may be somewhat shortsighted, given the vast heterogeneity of cerebral aneurysms in different locations. Therefore, ACoA lesions may be amenable to a separate randomized trial comparing microsurgical clipping with endovascular coiling to properly answer the question of equipoise. Patients included in ISAT were mostly those with good-grade aneurysmal subarachnoid hemorrhage whose lesions were located in the anterior circulation, but with advances in endovascular devices and techniques, the cohort included in the trial would likely be much more heterogeneous. Likewise, the rate of ACoA crossover seen in BRAT was probably higher than what would be seen in a new institutional trial today. Finally, comprehensive neurocognitive outcomes, although often not practical for large-scale trials, are needed in any new trials addressing the treatment of ACoA lesions, given the shortcomings of a dichotomized modified Rankin Scale. Including these considerations in future trial design will undoubtedly be beneficial as we strive to resolve age-old debates and evolve our traditional paradigms. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.