The Role of Anterior Circulation Patterns in Protecting from the Detrimental Effect of Vasospasm after Aneurysmal Sah due to Anterior Communicating Artery Rupture

Abstract

Introduction: Despite advances in neurocritical care, vasospasm following aneurysmal subarachnoid hemorrhage remains a potentially devastating entity. Several risk factors have been described, which include the amount of subarachnoid hemorrhage, age, smoking, and hypertension. Variations in the anatomy of the anterior circulation can play a role in the redundancy of blood supply to the distal anterior circulation. Four types of anatomical variation in regards to anterior communicating artery aneurysms (AComA) have previously been described: type 1—ICA supplies ipsilateral A1 and A2 and the AComA, with contralateral ICA supplying the A1 and A2 as well as the aneurysm, but no overt filling to contralateral circulation; type 2—ICA supplies ipsilateral A1, both A2's and the AComA, with contralateral ICA not supplying the A1; type 3—ICA supplies A1 and bilateral distal circulation, with contralateral ICA supplying contralateral A1 and A2, but not supplying the AComA; type 4—ICA fills A1, AComA and ipsilateral A2, Contralateral ICA fills A1 and A2, but not the aneurysm. Types 1 and 3 demonstrate some potential for cross-filling, whereas types 2 and 4 demonstrate absence of cross filling. Cross filling could potentially provide an element of redundancy in blood supply to the distal ACA territory. Objective: This study aims to elucidate the relationship between anterior circulation anatomy and vasospasm after AComA rupture. Cross-filling might confer an outcome advantage during vasospasm. Methods: A retrospective cohort review of 73 patients presenting with ruptured AComA to our institution from 2010 to January 2014 was performed by reviewing electronic patient records. The 21 patients with angiographic evidence of vasospasm were considered for further analysis. All aneurysms had been secured via microsurgical clipping or endovascular coiling depending on anatomical factors and clinical state. The presence of vasospasm was determined based on formal IR angiography. Results: The mean age of the patients was 51.24 ± 10.47 years and 29% (6/21) were males. Of the 26 patients, 13 (62%) patients were surgically clipped whereas 8 (38%) underwent coiling. Of the 21 patients with vasospasm, 3 (14%) were found to have type 1 anatomy, 6 (28%) had type 2, 6 (28%) type 3, and 6 (28%) had type 4 anatomy. Overall, 13 (61%) patients were discharged to home successfully, whereas 7 (33%) were discharged to rehab, and 1patient died. In the group demonstrating some potential for cross-filling (types1 and 3), 4 of 9 (44%) patients were discharged home in a stable condition, whereas in the group demonstrating no cross-filling (types 2 and 4), 9 of 12 (75%) patients were discharged home in a good condition. Conclusion: Even though a hypothesis of a protective effect with anterior circulation patterns showing the potential for cross-filling would make intuitive sense, our data does not support this hypothesis. Larger studies are indicated to confirm this deduction.