Persistent Trigeminal Artery

43-year-old female who presented for new onset dysarthria. The images demonstrate a focal region of T2/FLAIR hyperintense signal within the central pons with corresponding restricted diffusion. On the 3-D time-of-flight MRA portion of the examination, a diminutive basilar artery is identified with a prominent vessel extending from the internal carotid artery terminus on the left to supply the basilar tip. Imaging findings are compatible with a persistent primitive trigeminal artery. Persistent primitive trigeminal artery is typically unilateral. In utero, the trigeminal artery supplies the basilar artery prior to development of the posterior communicating and vertebral arteries. The persistent trigeminal artery arises from the junction between the petrous and cavernous internal carotid artery extending along the trigeminal nerve. As a result, the vertebral, posterior communicating, and inferior basilar arteries are typically hypoplastic.