Diversity among posterior thalamoperforating branches originated from P1 segment: systematic review

The P1 segment of the posterior cerebral artery (PCA) begins at the termination of the basilar artery and ends at the origin of posterior commu-nicating artery, within the interpeduncular cistern. Perforating branches arising from this segment are called posterior thalamoperforating arteries (TPAs) and the main and biggest artery among those is called TPA. Perforating branches are a crucial component of cerebrovascular system supplying the posterior part of the thalamus, subthalamus, hypothalamus, substantia nigra, perforated substance, posterior part of internal capsule and the nucleus of III and IV cranial nerve. It is very important for neurosurgeon to know the anatomy of perforating branches because of their susceptibility to injury. The aim of this study is to determine the morphometry of posterior TPAs and allow a better understanding of their bran-ching patterns and relation to basilar artery.

An extensive search was undertaken in order to identify published literature related to the posterior cerebral circulation system and the anatomy of posterior TPAs using key words. Medline, Embase, Ovid and Google Scholar databases were searched for publications dated from 1970 until July 2016. We collected and analysed all the data describing the mean number of branches per P1 segment, range of branches, number of analysed PCA, largest diameter of TPA, mean diameter of TPA and average distance from the basilar artery bifurcation.

Thirteen cadaver studies were analysed and the data was extracted. We focused on the mean number of branches arising from P1 segment, perforators range, mean diameter of perforating branches, largest diameter of perforating branches.

Mean number of branches per hemisphere was 2.91 (min. 1.51, max. 4.1). In more than half of analysed studies, authors did not find any pre-sence of posterior TPAs. Mean diameter of those perforators was 0.51 mm (min. 0.125 mm, max. 0.8 mm). Average distance from basilar artery bifurcation was 2.29 mm (min. 1.93 mm, max. 2.75 mm). There were many branching patterns presented by different authors.