Morphological Characteristics of the Thalamoperforating Arteries

Objective : The aim of this study was to investigate the morphological characteristics of the thalamoperforating arteries that arise from the P1 segment of the posterior cerebral artery. Methods : Thalamoperforating arteries located in the interpeduncular fossa were dissected in 26 formalin-fixed human cadaver brains. We investigated the origin site of thalamoperforating arteries from the PI segment, number and diameter, and variations in their origin. Results : Thalamoperforating arteries arose from the superior, posterior or posterosuperior surfaces of the P1 segment at the mean 1.93 mm (range, 0.41-4.71 mm) distance from the basilar apex and entered the brain through the posterior perforated substance. The average number was 3.6 (range 1-8) and mean diameter was 0.70 mm (range 0.24-1.18 mm). Thalamoperforating arteries could be classified into five different types according to their origin at the P1 segment : Type I (bilateral multiple), 38.5%, Type II (unilateral single, unilateral multiple), 26.9%; Type III (bilateral single), 19.2%, Type IV (unilateral single), 11.5%; Type V (unilateral multiple), 3.8%. In 15.4% of all specimens, thalamoperforating arteries arose from the only one side of PI segment and were not noted in the other side. In such cases, the branches arising from the one side of P1 segment supplied the opposite side. Conclusion : Variations in the origin of the thalamoperforating arteries should be keep in mind to perform the surgical clipping, endovascular treatment or operation involving the interpeduncular fossa. In particular, unilateral single branch seems to be very risky and significant for surgical technique or endovascular treatment.