Objective:

We sought to determine the association between circle of Willis (CoW) anatomical variations and outcomes in aneurysmal subarachnoid hemorrhage (aSAH) patients.

Background:

The impact of CoW anatomical variations on vasospasm risk and functional outcome in patients with aSAH is poorly understood.

Design/Methods:

We performed a retrospective study on a single center cohort of patients with aSAH admitted to an academic center between 2015 and 2022. After reviewing imaging, we classified CoW variants into 4 categories: 1) incomplete anterior segments if either proximal anterior cerebral or anterior communicating arteries were absent or hypoplastic (with a 1mm diameter cutoff), 2) incomplete posterior segments if posterior communicating or proximal posterior cerebral arteries were absent or hypoplastic; 3) complete CoW; 4) others. Outcomes include vasospasm based on transcranial Doppler (TCD) criteria and poor functional outcome defined as modified Rankin Scale 4-6 at 3 months post discharge. Binary logistic regression analysis was used to test the association of each CoW variant with outcomes.

Results:

We included 178 patients with aSAH (mean age 55.9 years [SD 13.6], 56% female). Eighty percent of patients had incomplete CoW and they were older than those with complete CoW (mean age 57.4 [SD12.7] vs 49.9 [15.4]; p=0.003). Incomplete posterior segments were seen in 73% of patients. The presence of incomplete anterior segments was more common in females (11% vs 1%; p=0.01) and it was associated with vasospasm (OR 2.39, 95% CI 1.02-5.63; p=0.042), but not with poor functional outcome (p=0.89). There was no association between incomplete posterior segments and vasospasm risk (p=0.29) or poor functional outcome (p=0.93).

Conclusions:

Anatomical variations of the CoW may affect TCD findings but did not appear to be associated with poor outcomes. Larger prospective studies are needed to explore clinical significance of CoW variants in aSAH patients.