Nomogram to predict aneurysmal origin of intracranial subarachnoid hemorrhage: a user-friendly tool for clinical decision making

Introduction: While intracranial aneurysm rupture is the most common etiology of intracranial subarachnoid hemorrhage (SAH), up to 20% of cases are reported to be of non-aneurysmal origin. There is lack of user-friendly prediction systems to aid in clinical decision making after initial negative angiogram to optimize further patient disposition and clinical management. We aimed to develop a predictive nomogram tool incorporating significant clinical and radiographic predictors of aneurysmal SAH.

Methods: Demographic, clinical, and radiographic data of non-traumatic SAH patients treated at our institution between 2013 and 2021 were collected and analyzed. Univariate and multivariate statistical analyses were performed yielding significant SAH origin predictors that were incorporated into a predictive nomogram.

Results: A total of 167 patients were included with 70 patients in the aneurysmal and 98 patients in the non-aneurysmal SAH groups. Univariate analyses identified patient sex (p=0.01), modified Fisher grades (p < 0.0001), presence of hydrocephalus (p < 0.0001) and intraventricular hemorrhage (p < 0.0001) to be significantly different between the aneurysmal versus non-aneurysmal origin SAH groups. Multivariate logistic regression identified hemorrhage presence in the suprasellar cistern (OR 8.4, 95% CI 2.6 – 32.1, p=0.0008), hemorrhage absence in the foramen magnum (OR 0.13, 95% CI 0.04 – 0.39, p=0.007) and hydrocephalus (OR 8.6, 95% CI 3.3 – 24.5, p< 0.0001) to be independent predictors of aneurysmal origin SAH. A nomogram incorporating these factors was created, internally validated, and confirmed using bootstrapping. It demonstrated good accuracy in estimating the risk of aneurysmal origin SAH with a C-index of 0.83 (95% CI 0.72 – 0.95).

Conclusion : Our study provides a convenient nomogram that incorporates easily identifiable factors determining aneurysmal origin of SAH. The nomogram can be easily used at the point-of-care setting to aid in disposition and clinical decision making in cases of initial angionegative SAH.