Primitive trigeminal artery.

A 29-year-old woman presented with a near-syncopal event, followed by right-sided weakness and numbness as well as dysarthria. The symptoms resolved over several hours. The patient had a history of migraine and cleidocranial dysostosis. Her work-up was negative for stroke and dissection. Computed tomographic angiography (Figure 1, A and B) showed a carotid to basilar artery anastomosis (persistent primitive trigeminal artery). This variant is present in 0.1% to 0.6% of angiograms1. Patients with cleidocranial synostosis may be prone to anomalies of the circle of Willis since they are more likely to harbor cerebral aneurysms (26%).2.