Intraventricular Hemorrhage Burden and Treatment-Specific Symptomatic Vasospasm After Aneurysmal Subarachnoid Hemorrhage.

Background/Objective: The modified Fisher scale classifies intraventricular hemorrhage (IVH) as present or absent, potentially obscuring meaningful vasospasm risk differences. This study aimed to identify the IVH burden threshold, measured by the Graeb scale, at which symptomatic vasospasm risk increases after aneurysmal subarachnoid hemorrhage (SAH) and whether this association differs by treatment modality. Methods: This retrospective single-center study included aneurysmal SAH patients undergoing microsurgical clipping or endovascular coiling between 2015 and 2025. IVH was graded using the original Graeb scale (range, 0-12) and categorized as no IVH (0), grades 1-3, 4-7, or ≥8. The outcome was symptomatic vasospasm. Multivariate logistic regression and exploratory subgroup analyses were performed. Results: Among the 307 patients analyzed (clipping, n = 224; coiling, n = 83), symptomatic vasospasm occurred in 63 (20.5%). On multivariate analysis, an IVH Graeb score ≥ 4 was the only independent predictor of symptomatic vasospasm (odds ratio, 4.32; 95% confidence interval, 2.10-8.87; p < 0.001). Exploratory subgroup analysis showed the clipping-coiling difference was most pronounced in Graeb 4-7 (18.2% vs. 62.5%; p = 0.008), with no significant differences in remaining categories. However, the treatment × Graeb-category interaction was non-significant (p = 0.066). Conclusions: An IVH Graeb score ≥ 4 independently predicted symptomatic vasospasm after aneurysmal SAH. The treatment-specific divergence observed in the Graeb 4-7 subgroup was exploratory and hypothesis-generating, suggesting that early cerebrospinal fluid diversion may warrant particular consideration when endovascular coiling is performed in patients with moderate IVH.