Angiographic "Tau (τ)" sign in persistent trigeminal artery

Abstract

Brain magnetic resonance imaging (MRI) of a 44-year-old lady done as part of the evaluation of non-specific headache, revealed a left side vascular anomaly. Neurologic examination was normal. MR-angiogram with Time Of Flight (TOF) sequence showed a persistent trigeminal artery on the left side extending backwards by the side of the sella from the internal carotid artery to the basilar artery [ Figure 1]. Coronal T2 and reconstructedimages showed that the artery was joining the basilar trunk below the origin of the superior cerebellar artery [ Figure 2]. The vertebrobasilar complex below the union was hypoplastic. Sagittal reconstructions showed that both posterior communicating arteries were absent and "tau" sign was present at the site of origin of the vessel from the internal carotid artery [ Figure 3].