A case of severe carotid artery stenosis associated with a collapse of the distal extracranial internal carotid artery: Special reference to the usefulness of the transoral carotid ultrasonography

We present a case that had an angiographical finding of a severe stenosis at the origin of the internal carotid artery (ICA) associated with diffuse luminal narrowing of the distal portion of the extracranial ICA on each side. To decide the indication of carotid endarterectomy, it is indispensable to evaluate the distal ICA that cannot be observed by conventional carotid ultrasonography. Transoral carotid ultrasonography (TOCU) enables us to measure the diameter, cross-sectional area, and flow velocity in the distal ICA. By means of TOCU, we diagnosed a narrowing of the distal ICA to be a collapse due to reduced perfusion pressure, and excluded the following possibilities: a thickened vessel wall with atherosclerosis or other organic lesions, hypoplastic vessel, and laminar flow by insufficient contrast medium. TOCU is a very useful tool to evaluate the distal extracranial ICA.