Background and Purpose—In acute stroke patients, the presence of a hyperdense middle cerebral artery sign on unenhanced CT is a specific but insensitive indicator of acute thrombosis. Our purpose was to determine whether the hyperdense basilar artery (HDBA) sign has utility in detecting thrombosis and predicting outcome in patients presenting with signs and symptoms of posterior circulation stroke.

Methods—Unenhanced CT scans obtained within 24 hours of symptom onset in 95 patients with suspected posterior circulation stroke were reviewed. Three neuroimagers blinded to clinical outcome and results of the concurrent CT angiography (which served as the reference standard) rated presence of HDBA sign on a 5-point scale for level of certainty (1=definitely absent; 5=definitely present). Receiver operating characteristic curve analysis was performed. Short-term outcome was measured by discharge National Institute of Health Stroke Scale (NIHSS) scores; long-term outcome was measured by 6-month modified Rankin score (dichotomized, poor outcome defined as modified Rankin score >2). The following variables were correlated with short-term and long-term outcome by univariate analysis: HDBA sign, age, sex, time from stroke onset to imaging, admission NIHSS, history of stroke/TIA, atrial fibrillation, coronary artery disease, hypertension, diabetes, hypercholesterolemia, tobacco use, and thrombolysis. Variables showing correlation with P<0.1 were included in multiple regression analysis.

Results—Using a level of certainty cutoff score of 4 (probable, definite), HDBA sign had 71% sensitivity, 98% specificity, 94% accuracy, 83% positive predictive value, and 95% negative predictive value for basilar artery occlusion. In univariate analysis, factors significantly correlated with discharge NIHSS were: admission NIHSS (P<0.0001; r=0.77), HDBA sign (P=0.01), and diabetes (P=0.02). Factors showing significant correlation or association with poor long-term outcome were age (P=0.02), admission NIHSS (P=0.007), HDBA sign (P=0.02), and history of stroke or TIA (P=0.007). The odds ratio of HDBA sign for predicting poor long-term outcome was 5.3 (95% CI, 1.1–33.3). In multiple regression analysis, the only independent predictors of discharge NIHSS were admission NIHSS (P<0.0001) and HDBA sign (P=0.004). Significant independent predictors of poor long-term outcome were age (P=0.02), admission NIHSS (P=0.008), history of stroke/TIA (P=0.03), and HDBA sign (P=0.05).

Conclusion—In patients presenting with a high pretest probability of posterior circulation stroke based on clinical symptoms, the presence of the HDBA sign on unenhanced CT is a strong predictor of basilar artery thrombosis, and both short- and long-term outcome.