Posterior projecting carotid bifurcation aneurysms.

Posteriorly projecting carotid bifurcation aneurysms are rare. Proximal anterior cerebral artery aneurysms are even more uncommon. Distinguishing between true posteriorly projecting carotid bifurcation aneurysms and carotid A1 aneurysms can be difficult but it is important because small posteriorly projecting carotid bifurcation aneurysms may need a contralateral approach for adequate exposure. We report our experience with a recent case that illustrated this problem.