Bilateral Persistent Trigeminal Artery Variants Diagnosed by MR Angiography

Abstract

A persistent trigeminal artery (PTA) is the most common anastomosis between the carotid and vertebrobasilar system. A PTA variant (PTAV) is a rare anomaly in which the cerebellar artery arises from the internal carotid artery (ICA) without connection with the basilar artery (BA). I present what I believe is the first report of bilateral PTAVs diagnosed using magnetic resonance (MR) angiography and briefly discuss the embryology of this rare anomaly. An 81-year-old woman with small infarctions underwent cerebral MR imaging and MR angiography with a 1.5-tesla imager for the evaluation of brain lesions. An MR angiography was obtained using the standard noncontrast three-dimensional time-of-flight technique. The MR angiographic demonstration of bilateral anterior inferior cerebellar arteries arising from the precavernous segment of the ICA without anastomosis to the BA indicated bilateral PTAVs. This is the first report of bilateral PTAVs diagnosed by MR angiography. The literature review indicates that an estimated prevalence of bilateral PTAVs is about 0.0012%.

A Functional Perspective on the Embryology and Anatomy of the Cerebral Blood Supply

“… 69 More rarely, the trigeminal system arising from the ICA supplies the cerebellar arteries directly, bypassing the BA. 73 This so called "persistent TA variant" is found in up to 0.2% of angiographic series and it is typically unilateral, although in even rarer instances, it can be found bilaterally (0.0012%). 73 , 74 A further subdivision of type 3 persistent TA has been suggested to incorporate the persistent TA variant and name it according to the cerebellar artery arising from the ICA.…”

“… 73 This so called "persistent TA variant" is found in up to 0.2% of angiographic series and it is typically unilateral, although in even rarer instances, it can be found bilaterally (0.0012%). 73 , 74 A further subdivision of type 3 persistent TA has been suggested to incorporate the persistent TA variant and name it according to the cerebellar artery arising from the ICA. Persistent TA type 3a, 3b, and 3c are named if the TA supplies directly the SCA, AICA, or PICA, respectively, the majority being Type 3b.…”