In surgery of carotid aneurysms below the bifurcation of the posterior communicating artery (C2-C3), dissecting the proximal internal carotid artery and the neck of the aneurysms is difficult. Unroofing of the optic canal and anterior clinoidectomy are well known methods of exposing the proximal side. In this paper, each method is discussed on the basis of our experience. Unroofing is an easy method of gaining a view of the medial aspect of the internal carotid artery (C2) and is suited for small aneurysms projecting medially; the so called suboptic type. However, this method is insufficient for large and proximal aneurysms where it is neccessary to get a more proximal view and to gain a wider space for applying variable clips. On the other hand, total removal of the anterior clinoid preocess permits visualization of more of the proximal internal carotid artery (C3 siphon) without entering the cavernous sinus. Furthermore, this technique makes a wide space around the proximal internal carotid artery by detaching a ring of dura. It is a promising technique for various types and sizes of proximal internal carotid artery aneurysms.
