[Dilated lesion at internal carotid artery posterior communicating artery junction].

The diagnosis and surgical indication of an incidental aneurysm at the IC-PC junction is sometimes vague. In this report, 28 lesions in 26 cases with aneurysmal dilatation at the IC-PC junction, which were surgically treated, were analyzed. These lesions are classified according to the operative findings. Only 6 of the lesions were confirmed to be true aneurysms. However, 19 lesions were the dilated changes of the posterior communicating arteries (Pcom) themselves, without aneurysmal formation. Two lesions were accompanied with blood blister like aneurysm at the wall. Another one was dilated Pcom with peripheral Pcom occlusion. The correlation between operative findings and angiographic findings are studied, and the importance of the diagnostic angiographic findings of the Pcom is strongly emphasized for their diagnostic value.