Persistent Hypoglossal Artery (PHA): Detailed Overview The persistent hypoglossal artery (PHA) is a rare developmental anomaly involving the persistence of an embryonic vessel that connects the internal carotid artery (ICA) to the basilar artery. It is one of the four transient embryonic carotid-vertebrobasilar anastomoses. 1. Embryology During embryonic development (4–6 weeks), temporary connections form between the carotid and vertebrobasilar systems. These include: Trigeminal artery Otic artery Hypoglossal artery Proatlantal intersegmental artery As the vertebral arteries develop from the fusion of cervical intersegmental arteries, these anastomoses normally regress. The hypoglossal artery originates from the ICA near the C1 segment and courses through the hypoglossal canal to reach the basilar artery. Failure of regression leads to a persistent hypoglossal artery. 2. Anatomy Origin: Arises from the ICA at the level of the C1 vertebra or the skull base. Course: Passes through the h