Surgical treatment of anterior circulation aneurysms

Abstract

With few exceptions, aneurysm surgery is preventive surgery; the aim is to prevent a subarachnoid hemorrhage from the aneurysm—rebleeding after the first hemorrage or possibly first bleeding from a previously unruptured aneurysm. Consequently, surgical mortality and morbidity must not exceed natural mortality and morbidity. The natural risk of death from rebleeds after aneurysmat subarachnoid hemorrhage is about 35% immediately after the bleeding, and decreasing quickly to a level of approximately 2%/y. The annual bleeding rate of previously unruptured aneurysms is traditionally considered to be about 1.4% but can be much lower. For good-grade patients, the ideal time of surgery after a subarachnoid hemorrhage is the first days after bleeding. For previously unruptured aneurysms, the timing of surgery is not critical. Of the open, intracranial procedures, clipping of the aneurysm neck is the only widely used procedure today. Intravascular treatment is a new and possibly good alternative to open operations for intracranial aneurysms; however, surgery is still the standard aneurysm therapy. To minimize operative mortality and morbidity, the best possible perioperative conditions must be created. Preoperatively, if the patient has had a recent subarachnoid hemorrhage, standard care includes maintenance of stable and normal blood pressure and nimodipine to prevent possible ischemic complications in addition to good general care. Perioperatively, it is important to prevent ischemic complications and to create the best possible operative conditions with respect to intracranial space. The most common anterior circulation aneurysm locations are internal carotid artery, anterior communicating artery, middle cerebral artery, and pericallosal artery. The approach to all these aneurysm locations, with the exception of pericallosal aneurysms, is the pterional one, with possible small variations. The general principle of dissecting an aneurysm is to follow the parent vessel and identify the aneurysm neck. The aneurysm neck always must be dissected free from surrounding arteries and clipped with one or more aneurysm clips. Techniques used vary according to the location, but common for all is avoiding a lesion to any important artery and achieving a complete closure of the aneurysm neck. It is particularly difficult and important to avoid closure of the socalled perforating arteries close to anterior communicating artery and internal carotid artery aneurysms.