Clinical study of enlarged infundibular dilation of the origin of the posterior communicating artery.

Although some aneurysmal dilations of the origin of the posterior communicating artery (PCoA) that are revealed on carotid angiogram are true aneurysms or preaneurysmal lesions, the authors warn that diagnosis should not be based only on the size and shape of the dilation, especially when the PCoA does not fill. In the present retrospective study, the authors analyzed intraoperative and angiographic findings in 32 patients with 34 lesions of the PCoA that were preoperatively diagnosed as aneurysms. Only 10 of the lesions were true aneurysms (six cases) or enlarged infundibular dilations with reddish bulges (that is, preaneurysmal bulge; four cases) at the origin of the PCoA. All of the other 24 lesions, including one lesion with PCoA occlusion, were merely enlarged infundibular dilations without any wall abnormality. A well-developed PCoA was observed only in cases of true aneurysm and dilation with reddish bulge. No other clinical or angiographic characteristics proved useful in identifying the type of lesions. These findings may be helpful to the physician in evaluating the clinical features of such lesions and in determining the diagnosis of enlarged infundibular dilation of the PCoA.