Peritruncal hematoma volume: is it a neglected prognostic marker in aneurysmal subarachnoid hemorrhage?

OBJECTIVE: Radiological severity scores for aneurysmal subarachnoid hemorrhage (aSAH), such as the modified Fisher scale (mFS), focus on supratentorial blood components. However, peritruncal blood is frequently present but remains underrepresented in current grading systems, despite the functional relevance of the brainstem. In the present study, authors aimed to investigate the association among peritruncal blood volume, aSAH-related complications, and clinical outcomes. METHODS: In this retrospective single-center study, aSAH patients with baseline CT imaging in the period from 2012 to 2022 were analyzed. Hematoma volumes in predefined peritruncal cisterns (interpeduncular, prepontine, premedullary, and magna) and ventricles (third and fourth) were manually segmented, and both individual and cumulative peritruncal volumes were analyzed. Associations with complications (ventriculoperitoneal shunt [VPS] dependency, macrovasospasm, and delayed cerebral ischemia [DCI]) and functional outcome (modified Rankin Scale score at discharge and 6 months) were assessed and compared to Fisher scale (FS) and mFS grades. RESULTS: Among the 675 patients included in this study, peritruncal cisternal and ventricular blood volumes were significantly associated with VPS dependency and functional outcome and had weaker associations with DCI. Across radiological parameters, cumulative peritruncal hematoma volume had a stronger association with functional outcome at discharge and 6 months than the Fisher-based scales; however, absolute model fit remained modest (pseudo-R2 0.141 and 0.139 vs FS 0.078 and 0.067; and vs mFS 0.098 and 0.090). Associations persisted in patients with low FS grades (≤ 2) and in those with anterior circulation aneurysms. CONCLUSIONS: Peritruncal blood volume is independently associated with outcome after aSAH and may be a clinically relevant marker in aSAH. Incorporating peritruncal components into current supratentorially based grading systems may enhance their predictive utility. These exploratory findings warrant prospective multicenter validation, and there is currently work focused on an "extended Fisher" approach that integrates infratentorial compartments.