Extent of hypoattenuation on CT angiography source images predicts functional outcome in patients with basilar artery occlusion

Background and Purpose-Quantification of early ischemic changes (EIC) may predict functional outcome in patients with basilar artery occlusion (BAO). We tested the validity of a novel CT score, the posterior circulation Acute Stroke Prognosis Early CT score (pc-ASPECTS). Methods-Pc-ASPECTS allots the posterior circulation 10 points. Two points each are subtracted for EIC in midbrain or pons and 1 point each for EIC in left or right thalamus, cerebellum or PCA-territory, respectively. We studied 2 different populations: (1) patients with suspected vertebrobasilar ischemia and (2) patients with BAO. We applied pc-ASPECTS to noncontrast CT (NCCT), CT angiography source images (CTASI), and follow-up image by 3-reader consensus. We calculated sensitivity for ischemic changes and analyzed the predictivity of pc-ASPECTS for independent (modified Rankin Scale [mRS] score <= 2) and favorable (mRS score <= 3) outcome. Results-Of 130 patients with suspected vertebrobasilar ischemia, 72% ( 94) had posterior circulation stroke, 8% ( 10) transient ischemic attack, and 20% (26) nonischemic etiology. Sensitivity for ischemic changes was improved with CTASI compared to NCCT (65% [95% CI, 57% to 73%] versus 46% [95% CI, 37% to 55%], respectively). Pc-ASPECTS score on CTASI but not NCCT predicted functional independence (OR 1.58; P = 0.005 versus 1.22; P = 0.42, respectively). Of 46 patients with BAO, 52% (12/23) with CTASI pc-ASPECTS score >= 8 but only 4% (1/23) with a score < 8 had favorable functional outcome (RR 12.1; 95% CI, 1.7 to 84.9). This difference was consistent in 21 patients with angiographic recanalization (RR 7.7; 95% CI, 1.1 to 52.1). Conclusion-The CTASI pc-ASPECTS score may identify BAO patients unlikely to have a favorable outcome despite recanalization.