Aneurysms and subarachnoid hemorrhage.

Most unruptured intracranial aneurysms that produce neuro-ophthalmologic signs arise from the junction of the internal carotid and posterior communicating arteries. These aneurysms typically compress the third nerve in the subarachnoid space. Compression of cranial nerves within the cavernous sinus is less common, resulting in single or multiple and often painful ocular motor nerve pareses. Unruptured aneurysms of the proximal and distal segments of the intracranial portion of the internal carotid artery can compress the anterior visual pathways and cause visual loss. Ocular symptoms and signs may be the presenting manifestations of intracranial aneurysms. Prompt recognition of an aneurysm prior to rupture can prevent devastating intracerebral or subarachnoid hemorrhage. Moreover, visual complications are a not infrequent source of morbidity in those patients surviving acute intracranial bleeding. Recent advances in noninvasive neuroimaging and endovascular therapies facilitate early diagnosis and treatment and therefore may limit such complications.