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.