Diagnostic performance of CT perfusion in detecting contralateral aplasia of the A1 segment in acute internal carotid artery occlusion

Background and objectives Acute occlusion of the internal carotid artery (ICA) accompanied by contralateral A1 segment agenesis (CA-A1) presents distinct clinical and radiological features. Differentiating CA-A1 from non-CA-A1 cases in acute ICA occlusion based on preoperative angiography images is challenging. We hypothesized that CT perfusion (CTP) could help to quickly and accurately recognize acute ICA occlusions with CA-A1 and that the double stent retriever (DSR) technique might improve radiological outcomes in ICA occlusion with CA-A1. Methods ICA occlusion cases were categorized into CA-A1 and non-CA-A1 groups. The diagnostic performance of CTP for CA-A1 was assessed, and radiological outcomes were compared between DSR and non-DSR groups in the CA-A1 group. Results A total of 281 cases of acute ICA occlusion were included: 34 with CA-A1 and 247 without CA-A1. Bilateral anterior cerebral artery (ACA) perfusion abnormalities on CTP were more frequent in the CA-A1 group (97.1% vs 5.3%, P<0.001). CTP showed 97% sensitivity, 95% specificity, and 95% accuracy for diagnosing CA-A1. Distal embolism into the ipsilateral ACA was more frequent in the CA-A1 group (29.4% vs 6.5%, P<0.001). Seven ICA occlusions with CA-A1 underwent the DSR technique as the first-line strategy. The risk of distal embolism into the ipsilateral ACA was significantly reduced compared with that in non-DSR cases (0% vs 40.7%, P=0.046). Conclusion CTP can accurately and quickly detect CA-A1 in acute ICA occlusion. Distal embolism into the ipsilateral ACA is common in the CA-A1 group, and the DSR technique significantly reduces its incidence, showing promise as a first-line strategy.