Angiographic diagnosis of small aneurysms of the posterior communicating artery.

Angiographic diagnosis of an aneurysm of the internal carotidposterior communicating arteries (ICA-PCoA) is usually straightforward [1 ], unless the aneurysm is small (< 5 mm) or the PCoA itself is not filled on carotid angiography. In the latter case, the aneurysm may be confused with an infundibulum. In 1964, Fox et al. [2 , 3] described five patients with subarachnoid hemorrhage, three of whom had intact infundibula at surgery. These investigators suggested vertebral angiography with carotid compression as a means to show the PCoA arising from the apex of the infundibulum. The reverse situation (i.e. , showing angiographically that a small aneurysm lies next to-not continuous with-the PCoA), however, has not been reported. We now describe five cases of surgically proved aneurysms in which the maneuver of Fox et al. was used to provide objective angiographic evidence of an aneurysm.