Persistent trigeminal artery (PTA) is a non-involuted embryonic vessel that connects the cavernous part of the internal carotid artery with the posterior circulation. It is classified into two types

Saltzmann type I: PTA supplies the distal vertebrobasilar arteries. The caudal basilar artery is absent with hypoplastic distal vertebral arteries.

Saltzman type II: PTA supplies the superior cerebellar arteries with the posterior cerebral arteries supplied by the posterior communicating artery.

A 77-year-old female presented with sudden onset aphasia and fatigue. Her MRI demonstrated acute infarcts in both the anterior (left frontal lobe) and posterior circulation (bilateral thalamus). Her CT angiogram demonstrated severe left internal carotid artery (ICA) stenosis and an ipsilateral Saltzman Type 1 persistent trigeminal artery (PTA) predominantly supplying the entire posterior circulation. This vascular supply implicates her severe left ICA stenosis as the singular culprit lesion for her atypical infarct pattern.

The trigeminal artery typically involutes during embryological development but is persistent in 0.12- 1.0% of the population. A PTA may be associated with cerebral aneurysms, vascular nerve compression syndromes, and stroke. Identification of a PTA may be critical to planning cerebrovascular or endoscopic transsphenoidal interventions. Carotid endarterectomy requires clamping the ICA which could precipitate catastrophic posterior circulation ischemia in this setting. This patient subsequently underwent uncomplicated left carotid endarterectomy utilizing shunting and intraoperative monitoring.