Incomplete circle of Willis due to the bilateral abnormal origin of posterior cerebral arteries and bilateral absence of posterior communicating arteries

Variations in the circle of Willis are common. However, incomplete formation of circle of Willis due to bilateral abnormal origin of posterior cerebral arteries and bilateral absence of posterior communicating arteries is very rare. We report an unusual case of abnormal origin of the right posterior cerebral artery from the right internal carotid artery and continuation of basilar artery as left posterior cerebral artery in a 60-year-old male cadaver. The posterior communicating arteries were absent on both sides; hence, the arterial circle of Willis was incomplete. Furthermore, clinical and surgical importance of this case and relevant literature is discussed. The case of bilateral abnormal origin of posterior cerebral arteries, bilateral absence of posterior communicating arteries, and incomplete formation of posterior segment of circle of Willis is very rare. Precise knowledge of such variations in the cerebral vasculature is essential for anatomists, clinicians, and neurosurgeons.