Trigeminal neuralgia caused by a new variant of persistent trigeminal artery associated with agenesis of internal carotid artery.

We report a hitherto undescribed persistent carotid vertebral anastomosis associated with ipsilateral internal carotid artery agenesis and bilateral duplication of the intradural vertebral arteries. This rare anomaly was detected on MRI, supplemented by CT angiography while evaluating for cause trigeminal neuralgia in a 37-year-old woman. The aberrant vessel was seen to cause thinning and lateral displacement of the left trigeminal nerve on CISS 3D images. Also noted was a bilateral vertebral artery duplication of the PSA variant with the posterior inferior cerebellar artery arising from the medial limb of the duplication on the left.