• Supada Prakkamakul, Nantaporn Pitakvej, Netsiri Dumrongpisutikul, and Sukalaya Lerdlum.
• Department of Radiology, King Chulalongkorn Memorial Hospital the Thai Red Cross Society, 1873 Rama IV road, Pathumwan, Bangkok, 10330, Thailand. supada.pr@gmail.com.
• Neuroradiology. 2017 Oct 1; 59 (10): 989-996.

PurposeFlame-shaped pseudo-occlusion of the extracranial internal carotid artery (ICA) is a flow-related phenomenon that creates computed tomographic angiography (CTA) and digital subtraction angiography (DSA) findings that mimic tandem intracranial-extracranial ICA occlusion or dissection. We aim to determine the diagnostic performance of mid-cervical flame-shaped extracranial ICA sign on CTA in hyperacute ischemic stroke patients.MethodsWe retrospectively included consecutive anterior circulation ischemic stroke patients presenting within 6 h of symptom onset who underwent 4D brain CTA and arterial-phase neck CTA using a 320-detector CT scanner during August 2012 to July 2015. Two blinded readers independently reviewed arterial-phase neck CTA and characterized the extracranial ICA configurations into mid-cervical flame-shaped, proximal blunt/beak-shaped, and tubular-shaped groups. 4D whole brain CTA was used as a reference standard for intracranial ICA occlusion detection. Diagnostic performance of the mid-cervical flame-shaped extracranial ICA sign and interobserver reliability were calculated.ResultsOf the 81 cases, 11 had isolated intracranial ICA occlusion, and 6 had true extracranial ICA occlusion. Mid-cervical flame-shaped extracranial ICA sign was found in 45.5% (5/11) of isolated intracranial ICA occlusions but none in the true extracranial ICA occlusion group. The sensitivity, specificity, PPV, NPV, and accuracy of the mid-cervical flame-shaped extracranial ICA sign for the detection of isolated intracranial ICA occlusion were 45.5, 100, 100, 92.1, and 92.6%, respectively. Interobserver reliability was 0.90.ConclusionThe mid-cervical flame-shaped extracranial ICA sign may suggest the presence of isolated intracranial ICA occlusion and allow reliable exclusion of tandem extracranial-intracranial ICA occlusion in hyperacute ischemic stroke setting.

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