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.
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%, =0.027), death (11.2% versus 1.5%; odds ratios [OR] 8.04 [95% CI, 1.07-60.12]; =0.042), or delayed cerebral ischemia (12.3% versus 3.1%; OR, 4.42 [95% CI, 1.03-18.95]; =0.045). Multivariate analysis revealed that Hunt-Hess grade 4 to 5 (OR, 3.13 [95% CI, 2.11-4.64]; 2 at 3 months), whereas dan-SAH was not (OR, 0.66 [95% CI, 0.25-1.73]; =0.40).
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).