Treatment of Intracranial Aneurysms: Clipping or Coiling? (2004)

Treatment choice for a cerebral aneurysm is based on several factors: the aneurysm’s location, its morphology, and our ability to minimize subsequent rebleeding. The traditional method of treatment for intracranial aneurysms has been surgical clipping. However, the use of endovascular coil embolization has been increasing in frequency since its introduction in 1991. Both surgery and the endovascular treatment of intracranial aneurysms have potential complications. One drawback of coil embolization is partial revascularization. As described in the case report by Bhatti et al. (1) in this issue of the Journal, another complication is aneurysmal regrowth. Bhatti et al. describe a patient with a recurrent third cranial nerve palsy, subsequent to aneurysmal regrowth months after coil embolization of an unruptured, left superior, cerebellar aneurysm. Durability of treatment is the main disadvantage of coiling. In one series, recurrent filling was demonstrated in 38 of 259 (14.7%) coil-embolized aneurysms. The feared outcome of aneurysmal regrowth, namely rebleeding, occurred in 3 of the 38 (7.9%) recurrent aneurysms (2). More significant treatment complications related to coil embolization are thromboembolic events and perforation of the aneurysm. A large series reported an incidence of thromboembolic events from 2.5 to 11%, with permanent deficits in 2.5–5.5% of cases (3–5). Another feared complication of endovascular treatment is aneurysm perforation, which occurred in 2–6% of cases in a recent series (6). This event is generally a more lethal complication during coiling than clipping, and it is treated by completion of aneurysm coiling with reversal of heparinization and placement of a ventriculostomy. In 2002, Molyneux et al. (6) reported the results of the International Subarachnoid Aneurysm Trial (ISAT), the first prospective, randomized trial of clipping versus coiling for ruptured aneurysms. In that trial, patients treated with clipping had a 30.6% chance of a poor outcome at 1 year, while those treated with coiling had a 23.7% risk of a poor outcome. Although there was not a significant difference in mortality, the absolute risk reduction for poor outcome at 1 year with coiling was 6.9%. Although these initial results at a 1 year average follow-up are very encouraging for coiling, the data must be interpreted with caution because the initial ISAT data also suggest that durability of endovascular treatment is a concern. During the 1-year follow-up period of the interim report, 2.6% of coiled patients suffered an intracranial hemorrhage after treatment, as opposed to 0.9% of clipped patients. If this difference were to persist, the 6.9% risk reduction at 1 year might soon disappear. In addition, more than four times as many coiled patients required re-coiling in the same short follow-up period. Subsequent follow-up reports from the ISAT study will be crucial in defining the durability of the benefit seen with coiling. Further limitations of the ISAT study include under-representation of patients with posterior circulation aneurysms and those who presented with a Glasgow Coma Scale score of <13. However, other nonrandomized series have shown significantly higher complication rates in surgically-treated basilar apex aneurysms compared with those treated with coil embolization (8). Most centers currently favor endovascular treatment for ruptured aneurysms at any location in patients in poor clinical condition (Glasgow Coma Scale score <13). Studies have demonstrated that early endovascular treatment in such patients can result in good functional recovery (9). In centers where a physician experienced in endovascular techniques is available, we believe this approach should be the first option for all Hunt-Hess Grade 4–5 patients with ruptured aneurysms who are amenable to coiling, that is, morphology. those that have a small neck in relation to the aneurysm sac. We even favor coiling in lower grade patients (Hunt-Hess Grade 1–3) who have surgically high-risk ruptured aneurysms, including superior hypophyseal aneurysms that produce a mass effect on the anterior visual pathway and posterior-pointing basilar apex aneurysms. Carotid-ophthalmic aneurysms, where the dome typically exerts mass effect on the optic nerve but the neck is often readily accessible to the surgeon, can be treated effectively by both means, but surgery may provide more immediate relief of mass effect if the aneurysm is large and causing visual loss by compression. Endovascular treatment of intracranial aneurysms is a field in evolution. Developing endovascular techniques such as balloon remodeling and intravascular stents may allow aneurysms with wide necks to become amenable to endovascular treatment. The drawback of stents is that they are thrombogenic. Microsurgical clipping also remains the mainstay of therapy when artery branches are adjacent to or incorporated into wide necked aneurysms, typical of the middle cerebral artery. Surgical technique maintains the patency of these arterial branches because the placement and shape of the clip can be manipulated to accommodate the angio-architecture of the aneurysm neck. Three dimensional rotational angiography has greatly assisted in the proper morphologic evaluation of intracranial aneurysms and adjacent cerebral vascular anatomy. Review of these data by the neurosurgeon and interventional neuroradiologist helps to determine whether the aneurysms meet criteria for coiling or clipping. Patients with intracranial aneurysms should ideally be treated in centers that provide a multidisciplinary approach, combining the expertise of each specialist. (7)