CT angiography source images predict final infarct extent in patients with basilar artery occlusion

Abstract

Background and purpose: The posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) is a 10-point grading system to quantify ischemic changes in the posterior circulation. We analyzed whether pc-ASPECTS on CT angiography (CTA) source images (CTASI) predicted the final infarct extent and hemorrhagic transformation (HT) rate in patients with basilar artery occlusion.

Materials and methods: A pc-ASPECTS score of 10 indicates absence of visible ischemic changes in the posterior circulation, and pc-ASPECTS score of 0 indicates ischemic changes in the midbrain, pons, and bilateral thalami, posterior circulation territories, and cerebellar hemispheres. We retrospectively studied patients with basilar artery occlusion on CTA within 24 hours from symptom onset. We applied pc-ASPECTS to noncontrast CT (NCCT), CTASI, and follow-up images by 3-reader-consensus and assessed HT on follow-up images. We calculated Spearman correlation coefficients and performed linear regression analysis. Final infarct extent and HT rates were compared across dichotomized CTASI pc-ASPECTS groups (>/= 8 vs < 8).

Results: Among 43 patients, median (range) onset to CTA time was 5.0 hours (range, 0.7-24 hours). Pc-ASPECTS on CTASI (r = 0.75; P < .001) but not NCCT (r = 0.29; P = .063) correlated with pc-ASPECTS on follow-up scans. Linear regression demonstrated a significant positive relationship between pc-ASPECTS on CTASI and follow-up scans (R(2) = 0.58; P < 01). Median follow-up pc-ASPECTS was lower in patients with a CTASI pc-ASPECTS < 8 compared with patients with a CTASI pc-ASPECTS of 8 or more, respectively (P < .001). HT rates were 27.3% vs 9.5%, respectively (P = .24). None of 8 patients without thrombolysis had HT on follow-up scans.

Conclusions: The extent of hypoattenuation on CTASI predicts the final infarct extent in patients with basilar artery occlusion.

Fig 1.

Scatterplot of pc-ASPECTS scores on CTASI and NCCT compared with the pc-ASPECTS score on follow-up images. Larger symbols represent a larger number of patients at each data point. The estimated lines are derived from simple linear regression equations. CTASI (R² = 0.58, p < 0.001; slope = 0.68) results in lower variance around the point estimate of the slope of the line compared with NCCT. (R² = 0.13, p = 0.02; slope = 0.18).

Fig 2.

Comparison of median baseline pc-ASPECTS scores on NCCT and CTASI according to categorized follow-up pc-ASPECTS scores (box-whisker plot). Follow-up pc-ASPECTS category 0 to 3 indicates large, 4 to 7 medium-sized, and 8 to 10 small final infarct size.

Fig 3.

The pc-ASPECTS score on NCCT (A,D) was rated as 8 (early ischemic changes left mesencephalon; arrow). CTASI (B,E) demonstrate additional hypoattenuation in the left thalamus (arrows). The pc-ASPECTS score was rated as 7. On follow-up NCCT (C,F), the patient had PH with intraventricular hemorrhage. The follow-up pc-ASPECTS score was rated as 7 (mesencephalon and left thalamus).