Abnormal posterior circulating artery morphology Posterior communicating artery aneurysm 2018-01-27T11:27:22Z A widening (ballooning) localized in the wall of the posterior communicating artery. Posterior communicating artery aneurysm can leads to an acute palsy of the third cranial nerve with ipsilateral pupil dilation. Posterior communicating aneurysms can be classified into aneurysms that project laterally and below the tentorial incisura and cause oculomotor nerve compression, and aneurysms that project laterally above the tentorium that can manifest as temporal lobe hematoma if they rupture.