Perfusion-Derived Dynamic 4D CT Angiography Identifies Carotid Pseudo-Occlusion in Hyperacute Stroke

BACKGROUND: Differentiation between true acute tandem occlusion involving the extracranial internal carotid artery (ICA) from pseudotandem occlusion with a patent extracranial ICA has important prognostic and therapeutic implications. We explored the utility of perfusion-derived 4-dimensional CT angiogram (4D-CTA) in identifying carotid pseudo-occlusion in a single-center pilot study. METHODS: Acute stroke patients with delayed antegrade ICA flow on 4D-CTA despite an apparent tandem occlusion on conventional single-phase CTA were prospectively identified over a 2.5-year period (2013-2015). RESULTS: Eight patients were identified. Delayed antegrade intracranial flow from the apparently occluded ICA was detected up to 50 seconds after contrast administration on 4D-CTA. The distal intracranial ICA was the most common site of true occlusion. Reconstruction of the 4D-CTA images required an additional processing time of 2–3 minutes. CONCLUSIONS: 4D-CTA is a novel noninvasive technique that can identify carotid pseudo-occlusion in the acute stroke setting. Our preliminary findings suggest that 4D-CTA can be easily incorporated into an existing acute stroke neuroimaging protocol.