Intracranial Aneurysms Causing Ophthalmoplegia

Most aneurysms of the circle of Willis that give rise to ophthalmoplegia may be classified into three anatomoclinical types: (1) First, there are the dilatations of the internal carotid artery in the cavernous sinus. These may be congenital but are generally arteriosclerotic and are calledinfraclinoidaneurysms because they appear by arteriography to be silhouetted beneath the level of the clinoid processes. (2) Secondly, there are the saccular or berry aneurysms that arise at the sites of branching of the carotid artery. They are thought to be congenital in origin (although arteriosclerosis may play an importantly correlative role) and are situated above and behind the cavernous sinus. They are calledsupraclinoidaneurysms because their origin is silhouetted, when seen in arteriograms, above the level of the clinoid processes. (3) Thirdly, there are the dilatations of the basilar or vertebral arteries. These may be saccular and congenital in origin but are