Cervical Internal Carotid Occlusion versus Pseudo-occlusion at CT Angiography in the Context of Acute Stroke: An Accuracy, Interobserver, and Intraobserver Agreement Study

Purpose: To evaluate the diagnostic accuracy and reliability of computed tomographic (CT) angiography to distinguish true cervical internal carotid artery (ICA) occlusion from pseudo- occlusion (defined as an isolated intracranial thrombus that impedes ascending blood flow) in the context of acute stroke. Materials and Methods: This was a retrospective study of patients who underwent thrombectomy with preprocedural CT angiography that helps to demonstrate a lack of attenuation in the cervical ICA on the symptomatic side (24 men and 13 women; mean age, 63 years; age range, 30-86 years). Seven readers, including five neuroradiologists and two interventional neuroradiology fellows, independently reviewed the CT angiography images to assess whether there was true cervical ICA occlusion. Their results were compared with digital subtraction angiography (DSA) as the reference standard. Sensitivity and specificity for detecting true occlusion as well as accuracy and diagnostic odds ratio were calculated, with inter-and intraobserver k statistics. Results: Cervical ICA pseudo- occlusion occurred in 12 of 37 patients (32.4%) with nonattenuation of the cervical ICA on the symptomatic side. Interobserver agreement coefficients did not reach the substantial value of 0.61 for either pairs or groups of readers. The cohort's average sensitivity and specificity was 68% (95% confidence interval [CI]: 59%, 76%) and 75% (95% CI: 71%, 80%), respectively, with a diagnostic odds ratio of 8 (95% CI: 3, 18) and only fair interobserver agreement (k = 0.32; 95% CI: 0.16, 0.47). Conclusion: In the context of acute ischemic stroke with ipsilateral ICA nonattenuation at single-phase CT angiography, even specialized radiologists may not reliably distinguish true cervical occlusion from pseudo- occlusion. (C) RSNA, 2017