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Riles type 1A common carotid artery occlusion diagnosed by specific external carotid artery Doppler waveform pattern in carotid ultrasonography. Case report.

A 67-year-old man was admitted for evaluation of left homonymous hemianopsia. Carotid ultrasonography showed that the right common carotid artery (CCA) was occluded up to just proximal to the carotid bifurcation, and the patent external carotid artery showed retrograde flow to the patent internal carotid artery via the carotid bifurcation. The Doppler waveform pattern of the external carotid artery showed high end-diastolic flow velocity and low pulsatility index. The diagnosis was Riles type 1A CCA occlusion. Digital subtraction angiography and iodine-123 N-isopropyl-p-iodoamphetamine single photon emission computed tomography were performed to confirm the collateral circulation and adequate intracranial hemodynamic sufficiency. Nonsurgical treatment with antiplatelet therapy was performed for the CCA occlusion. No stroke events have occurred within the 2-year follow-up period.