Isolated Stenosis of a Persistent Hypoglossal Artery Visualized at 3D CT Angiography

Summary: The persistent hypoglossal artery is a rare per-severance of an embryonic vessel connecting the anterior and posterior circulations and is generally considered to be an incidental finding. This is a case of a patient with an atherosclerotic narrowing at the origin of the persistent hy-poglossal artery seen at 3D CT angiography. The pertinent findings and clinical implications of this anomalous vessel are discussed. The persistent hypoglossal artery (PHA) is one of four primitive connections between the anterior and posterior circulations that normally regress in utero. Of the four, the persistent trigeminal artery makes up the vast majority, with the PHA a distant second. These vessels have some clinical impor-tance when they are associated with aneurysms or arteriovenous malformations, or when carotid end-arterectomy is considered, but are generally inci-dental findings. There are a few reports of athero-sclerotic plaque extending from the distal internal carotid artery (ICA) into the PHA, although this is the first reported case of an isolated PHA stenosis. Case Report A 65-year-old woman had a left carotid bruit discovered on routine physical examination when she presented with elevated blood pressure. A carotid duplex study showed calcified plaque without stenosis at the left carotid bifurcation. Elevated velocities were found in the high left ICA, corresponding to a high-grade stenosis, although no stenosis was present in the proximal and mid-portions of the ICA. CT angiography was performed after administration of 120 mL of contrast material at 3 mL/s with an 11-second delay with real-time 3D volumetric reconstructions (1-mm-thick sections) and showed a large PHA entering a slightly enlarged left hypoglossal canal and forming the basilar artery (Fig 1). There was no left vertebral artery and only a very small right vertebral artery that primarily fed the right posterior inferior cer-ebellar artery. No communicating arteries were present. The PHA had a 60 % to 70 % stenosis just beyond its origin, corresponding to the elevated velocities seen on duplex scans. Calcified plaques were present in the ICA just proximal to the takeoff of the PHA, but no significant stenosis was present