Impact of intracranial atherosclerosis burden on vasospasm risk and outcomes in aneurysmal subarachnoid hemorrhage

Background: Cerebral vasospasm is a well-known complication after aneurysmal subarachnoid hemorrhage (aSAH) and occurs more commonly in younger patients. We hypothesized that intracranial atherosclerosis, which is seen predominantly in older patients, affects vasospasm risk. We sought to determine association between intracranial atherosclerosis burden with vasospasm and outcomes in aSAH. Methods: We retrospectively reviewed a cohort of consecutive patients with aSAH admitted to a Comprehensive Stroke Center between 2016 and 2023. Intracranial atherosclerosis burden was quantified by using modified Woodcock (MW) score on CT angiograms. Vasospasm was defined based on transcranial Doppler (TCD) criteria. Poor outcome was defined as 3-month modified Rankin Scale 3-6. Results: We reviewed 392 patients and included 302 (mean age 56.8 years [SD 13.3], 65 % female and 70 % white) in the final analysis. MW scores were measured with excellent intra-rater and inter-rater reliability (Cohen's kappa coefficient 0.9 and 0.83 respectively) ranging from 0 to 3 (mean 0.59, SD 0.83) with higher scores in older patients (beta coefficient 0.019, 95 % CI 0.009-0.028; p < 0.001). Higher MW calcification score was associated with lower risk of vasospasm (OR 0.52 per point increase, 95 % CI 0.36-0.78; p = 0.001). There was an inverse correlation between MW scores and severity of vasospasm (beta coefficient -0.29, 95 % CI -0.48, -0.1; p = 0.003). However, MW score was not independently associated with poor functional outcome (p = 0.62). Conclusions: Intracranial atherosclerosis is a potential mechanism for lower TCD-based vasospasm in older patients with aSAH; however, it may not impact functional outcomes. Larger prospective studies are needed to confirm our findings.