The Persistent Hypoglossal Artery is a persistent primitive connection between the carotid and vertebrobasilar arteries. The artery arises from the ICA (around the C1 to C3 levels) and traverses through the hypoglossal canal to join the basilar artery. The ipsilateral vertebral artery and posterior communicating artery may be hypoplastic or absent. 

Above: Persistent Hypoglossal Artery in AP and Lateral Views. There is also a basilar artery fenestration noted.

It can be difficult to tell which persistent carotid-vertebrobasilar anastomosis is present. Cross-sectional imaging is key. The Persistent Hypoglossal Artery should pass through the hypoglossal canal.

Picture Above: Persistent Hypoglossal Artery traversing the hypoglossal canal.