Variation in the origin of the posterior cerebral artery in adult Sri Lankans

Background: The degree of contribution from the vertebro-basilar and carotid systems to the origin of the posterior cerebral artery (PCA) is of clinico-anatomical importance. Three configurations in the bifurcation of the posterior communicating artery (PcomA) have been described, foetal, transitional and adult. Objective: To examine the extent of contribution from the vertebro-basilar and carotid systems to the origin of the PCA in adult autopsy brains in subjects who had died of causes unrelated to the brain. Materials and Methods: The external diameter of the PcomA, pre communicating part (P1) and the post communicating part (P2) of PCA in 225 normal Sri Lankan adult cadaver brains was measured using a calibrated grid. Results: The adult configuration was present in 220 (93.3%); (bilaterally in 200 (88.8%), and unilaterally in 20 (8.8%) ten on each side. Foetal configuration was seen in 17 (4.4%); bilaterally in 3 (1.3%), and unilaterally in 14 (6%) 8 on the left and 6 on the right. Transitional configuration was seen in 8 (2.2%); bilaterally in 2 (0.9%), and unilaterally in 6 (2.5%) 2 on the left and 4 on the right. Conclusion: This study reveals that the internal carotid artery (ICA) provided the major supply to the PCA in 4.4% of foetal and 2.2% of transitional configurations. The adult configuration was present in 220 (93.3%), the highest recorded in the literature. This finding may be of relevance to vertebrobasilar ischaemia and infarcts in the territory of the PCA.