The ABCs of Subarachnoid Hemorrhage Blood Volume Measurement: A Simplified Quantitative Method Predicts Outcomes and Delayed Cerebral Ischemia

Abstract

Background: We developed a simplified ABC/2-derived method to estimate total subarachnoid hemorrhage volume (SAHV) on noncontrast computed tomography in patients with aneurysmal SAH and compared the clinical and radiographic outcomes.

Methods and results: In this retrospective observational cohort study, we analyzed 277 patients with SAH admitted to our Comprehensive Stroke Center between 2012 and 2022. We derived a mathematical model (model 1) by measuring SAH basal cisternal blood volume using an ABC/2-derived ellipsoid formula (A=width/thickness, B=length, C=vertical extension) on head noncontrast computed tomography in 5 major SAH cisternal compartments. We compared model 1 against a manual segmentation method (model 2) on noncontrast computed tomography. Data were analyzed using logistic regression analysis, t test, receiver operator characteristic curves, and area under the curve analysis. There was no significant difference in cisternal SAHV analysis between the 2 models (P=0.14). Mean SAHV by the simplified method was 7.0 mL (95% CI, 5.89-8.09) for good outcome and 16.6 mL (95% CI, 13.49-19.77) for poor outcome. Patients with delayed cerebral ischemia had higher SAHV, with a cutoff value of 10 mL.

Conclusions: Our simplified ABC/2-derived method to estimate SAHV is comparable to manual segmentation and can be performed in low-resource settings. Higher total SAHV was associated with worse outcomes and higher risk of delayed cerebral ischemia. A potential dose-response relationship was observed, with SAHV >10 mL predicting worse outcomes and higher risk of DCI.

Keywords: ABC/2‐derived volumetrics; aneurysmal subarachnoid hemorrhage; clinical outcomes; delayed cerebral ischemia; subarachnoid hemorrhage volume.

Figure 1. Volumetric analysis via ABC/2‐derived subarachnoid hemorrhage volume (SAHV).

A, Multiple noncontrast computed tomography (CT) slice findings of a patient with aneurysmal subarachnoid hemorrhage. There are visible SAH hyperdensities in multiple cisternal compartments, marked with lines to determine length and width of the respected hemorrhage in millimeters. Measurements of width, length, and vertical extension (number of noncontrast CT slices with visible SAH) were performed in consideration of cisternal anatomy. B, Illustration of the 5 SAHV compartments measured Created in BioRender. Freeman, W. (2022) BioRender.com/t05a503. C, These metric variables were then inputted into our model 1 ABC/2‐derived SAHV equation to measure the hemorrhagic volume in each neuroanatomic structure. Each volume was then summed to a cumulative total SAHV.

Figure 2. Comparison of hemorrhagic volumes via volumetric estimation using ABC/2‐derived subarachnoid hemorrhage volume (SAHV; model 1 [M1]) versus segment SAHV (model 2 [M2]).

Average volume per cistern depending on different methods applied. Five SAH spaces or compartments. Significance testing by unpaired t test. ITV indicates interhemispheric total volume; ns, not significant; PMTV, perimesencephalic total volume; PTV, pontine total volume; SSTV, suprasellar total volume; and SYTV, sylvian total volume.

Figure 3. Relationship of estimated hemorrhagic volumes with target variables.

A and D, Mean volumes based on dichotomization into good outcome (modified Rankin scale [mRS] score 0–3) and poor outcome (mRS score 4–6) and the respective method (ABC/2‐derived SAHV) applied to estimate these volumes. Results are shown in Table 2. B, Receiver operating characteristic (ROC) curve of ABC/2‐derived subarachnoid hemorrhage volume (SAHV) on outcome at discharge with an area under the curve (AUC) of 0.78 (95% CI, 0.71–0.84). C, ROC curve of modified Fisher scale (mFS) on outcome at discharge with an AUC of 0.71 (95% CI, 0.64–0.78). E, ROC curve of ABC/2‐derived SAHV on delayed cerebral ischemia (DCI) with an AUC of 0.71 (95% CI, 0.63–0.79). F, ROC curve of mFS on the presence of DCI with an AUC of 0.67 (95% CI, 0.59–0.75).

Figure 4. ABC/2‐derived subarachnoid hemorrhage volume (SAHV) Youden index (J = sensitivity + specificity – 1) for each value of predictor variables.

Dashed lines indicate maximum Youden index. A, J_ABC‐SAHV‐outcome=10.086 mL. B, J_ABC‐SAHV‐DCI=10.117 mL. DCI indicates delayed cerebral ischemia.