Introduction: Aneurysmal SAH has a 28-day fatality rate of 31-39%, largely caused by vasospasm and subsequent delayed cerebral ischemia (DCI). DCI is historically difficult to predict. Existing imaging metrics have thus estimated vasospasm risk but have suboptimal predictive value and are operator dependent.

Methods: CT scans from 26 consecutive aSAH patients (CY2013) were analyzed using semiautomated software to obtain a ratio of intracerebral blood versus parenchymal tissue based on Hounsfield units. This blood/brain ratio (BBR) was tested as a predictor variable for radiographic vasospasm (rVS) as measured by angiography.

Results: The BBR is a strong predictor of rVS (figure 1). Average BBR for patients with rVS was 13.72 (without rVS =4.17, p<.001). In addition, when BBR was used as a blinded predictor of eventual rVS using ROC anaylsis, BBR was extremely accurate (AUC = 0.90).

Conclusions: Vasospasm and DCI are major determinants of outcome in patients with aSAH. Accurate risk stratification might allow clinicians to pre-empt morbidity by increasing cerebral perfusion prior to DCI. Our method is easy to implement and gives a single continuous variable that accurately predicts rVS with high accuracy.

Patient Care: Accurate and reliable prediction of vasospasm will allow clinicians to pre-empt the possible morbidity and mortality of delayed cerebral ischemia in patients after subarachnoid hemorrhage.

Learning Objectives: By the end of this session, participants will be able to apply a simple semi-automated computer algorithm to presenting CT scans to accurately predict radiographic vasospasm risk.

References: Fisher C, Kistler J, Davis J (1980). "Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning". Neurosurgery 6 (1): 1–9.