Transoral carotid ultrasonography for evaluating internal carotid artery occlusion

Background and Purpose Transoral carotid ultrasonography (TOCU) has enabled the assessment of the distal portion of the extracranial internal carotid artery (ICA). We evaluated the ultrasonographic features of ICA occlusion using TOCU. Methods We studied 50 occluded ICAs in 42 stroke patients. The mechanism of ICA occlusion was embolic (group E) in 14 arteries and thrombotic (group T) in the other 36 arteries. We used a color flow imaging system equipped with special convex array transducers, and placed the probe on the postero-lateral pharyngeal wall to identify the distal extracranial ICA. We evaluated intraluminal echodensity (lucent or opaque) and measured the diameter of the ICA. Then, we examined the relationship of these early (< 1 week after onset) and chronic (> 4 weeks after onset) phase TOCU findings to the mechanism of ICA occlusion and the site of occlusion. Results In the early phase of a stroke, the intraluminal echodensity was more frequently lucent (9/11, 81.8%) in group E than in group T (5/20, 20%, p < 0.05). In the chronic phase, echodensity became opaque in both groups. In the early phase, the lucent echodensity was more frequently seen in patients with distal occlusion than in those with proximal occlusion. Thus, it may represent blood or fresh thrombus formation. In patients with unilateral ICA occlusion, the occluded ICA was significantly smaller in diameter than the non-occluded contralateral artery both in the early and chronic phases. Conclusion The echodensity and diameter of the extracranial ICA distal portion as found on TOCU can help to identify the mechanism of ICA occlusion.