Zhang, Shihao

Background and purpose The use of computed tomography angiography (CTA) as the sole vascular imaging study for preoperative planning for clipping of aneurysms is well described in the literature. CTA is widely available, provides quick acquisition, has low morbidity, and low cost. In this study, we describe the accuracy of CTA in determining the blood supply dominance in comparison to standard digital subtraction angiography. Materials and methods Sixty-six patients, with both CTAs and angiograms, were reviewed by two independent neuroradiologists. The posterior cerebral artery was determined to have dominant supply from the posterior communicating artery if it was of similar size to the P2 segment and the P1 segment was smaller by approximately 50%. If the posterior communicating artery and P1 segment were the same size, it was considered to have a dual supply. If P1 and P2 segments were the same caliber and the posterior communicating artery was smaller by 50%, it was deemed to have posterior circulation dominance. Results Based on the findings of our reviewers, CTA had a sensitivity and specificity of 69% and 96%, respectively, in predicting the presence of a fetal PCA. The positive predictive value was found to be 82% while a negative predictive value was estimated as 93%. A small-caliber P1 segment and large-caliber posterior communicating artery led to inaccurate interpretations of the CTAs. Conclusion This study shows that one cannot accurately predict blood supply dominance of the posterior cerebral artery. Knowledge of the blood flow dominance is essential when clipping a posterior communicating artery aneurysm to avoid compromise in posterior circulation.

Background Preoperative assessment of anterior communicating artery (AcoA) aneurysms with cerebral angiography is common, but not without risk. Computed tomography angiography (CTA) is a widely available imaging modality that provides quick acquisition, low morbidity, and low cost. One disadvantage is that it does not provide dynamic information. In this study, the authors sought to determine whether CTA alone can reliably predict the inflow dominance to an AcoA aneurysm. Methods Eighty-three patients with ruptured AcoA aneurysms were reviewed retrospectively. Only those patients with both preoperative CTA and cerebral angiogram were included, thus excluding six patients. Four independent observers reviewed the CTAs and attempted to identify the dominant A1. Additionally, three mathematical models were created to identify the dominant A1. These responses were compared to cerebral angiograms. Results Four observers were correct in judging the dominant A1 an average of 93% of the time. Seventeen cases were read incorrectly by only one of four observers, and three cases were read incorrectly by two observers. For cases with incorrect readings, the average percentage difference in A1 sizes was 19.6%. For cases read unanimously correct, the average percentage difference in A1 sizes was 42.7%. Mathematical model #3 correctly evaluated the dominant A1 in 97% of the cases. Conclusions This study found CT angiograms can be reliable in predicting the inflow dominance to the majority of AcoA aneurysms.