Clinical Outcomes of Diffuse Angiogram‐Negative Subarachnoid Hemorrhage Versus Aneurysmal Subarachnoid Hemorrhage: A Propensity Score‐Matched Analysis

Background The outcome of diffuse angiogram‐negative subarachnoid hemorrhage (dan‐SAH) compared with aneurysmal SAH (aSAH) remains unclear. This study aimed to compare outcomes using propensity score matching. Methods and Results Sixty‐five patients with dan‐SAH and 857 patients with aSAH admitted between January 2018 and December 2022 were retrospectively reviewed. Propensity score matching resulted in matching 65 patients with dan‐SAH to 260 patients with aSAH, and clinical outcomes were compared between the groups. Compared with patients with dan‐SAH, patients with aSAH were more likely to experience rehemorrhage (8.8% versus 0%, P =0.027), death (11.2% versus 1.5%; odds ratios [OR] 8.04 [95% CI, 1.07–60.12]; P =0.042), or delayed cerebral ischemia (12.3% versus 3.1%; OR, 4.42 [95% CI, 1.03–18.95]; P =0.045). Multivariate analysis revealed that Hunt–Hess grade 4 to 5 (OR, 3.13 [95% CI, 2.11–4.64]; P <0.001), presence of intraventricular hemorrhage (OR, 3.58 [95% CI, 1.72–7.46]; P =0.001), and smoking (OR, 2.44 [95% CI, 1.12–5.28]; P =0.024) were independently associated with the incidence of unfavorable outcomes (modified Rankin scale score >2 at 3 months), whereas dan‐SAH was not (OR, 0.66 [95% CI, 0.25–1.73]; P =0.40). Conclusions Compared with patients with dan‐SAH, patients with aSAH had higher rehemorrhage rates and in‐hospital mortality, as well as a higher incidence of delayed cerebral ischemia. Unfavorable outcomes were associated with admission Hunt–Hess grade, the presence of intravenetricular hemorrhage, and smoking history, but there was no relation with the pathogenesis of the hemorrhage (dan‐SAH versus aSAH).