Forensic consequences of anatomical variants in cerebral vascularization - the case of bihemispheric posterior inferior cerebellar artery

Abstract

The anatomy of the posterior inferior cerebellar artery (PICA) has a wider variability compared to the superior cerebellar artery (SCA) or the anterior inferior cerebellar artery (AICA). The PICA with bihemispheric distribution (bPICA) can be found in less than 0.1% of cases. We report here a rare such case, documented by anatomical microdissection. A true right bPICA was found emerging the origin of the basilar artery. From its lateral medullary segment the equivalent of the rostral trunk of an AICA was leaving, and from the tonsillomedullary segment of the bPICA emerged a trunk distributed in the territory of the caudal branch of the AICA. The telovelotonsilar segment of that bPICA was further sending off the PICAs proper, ipsilateral and contralateral. Each of these was supplying equally the vermis and the cerebellar hemisphere. The contralateral PICA proper was also distributed in the territory of the caudal trunk of the AICA, while the rostral trunk of the absent AICA was supplied by the SCA. Radiologists and surgeons should be aware of this variant, to diagnose it accurately, avoid pitfalls in diagnosis of bilateral cerebellar infarcts, and to avoid its damage during the microsurgical exposures.