Clipping vs Coiling for Ruptured Intracranial Aneurysms

Abstract & Commentary

By Matthew E. Fink, MD Dr Fink is Vice Chairman, Professor of Clinical Neurology, Weill Medical College, and Chief, Division of Stroke and Critical Care Neurology, New York-Presbyterian Hospital. Dr. Fink reports no consultant, stockholder, speaker's bureau, research, or other relationship related to this field of study.

Synopsis: In a randomized trial of neurosurgical clipping versus endovascular coiling for ruptured intracranial aneurysms, endovascular coiling was more likely to result in independent survival at 1 year.

Source: Molyneux AJ, et al. International Subarachnoid Aneurysm Trial (ISAT) of Neurosurgical Clipping Versus Endovascular Coiling in 2143 Patients with Ruptured Intracranial Aneurysms: A Randomized Comparison of Effects on Survival, Dependency, Seizures, Rebleeding, Subgroups, and Aneurysm Occlusion. Lancet. 2005;366:809-817.

The ISAT trial closed recruitment and published preliminary results (Lancet. 2002;360:1267-1274.) after an interim analysis showed the benefit of endovascular treatment on the primary outcomes: death or dependency at 1 year. This report gives the final results after complete follow-up of all randomized patients.

The 2143 patients with ruptured intracranial aneurysms, who were appropriate candidates for either clipping or coiling, were randomized to either group, treated at a neurosurgical center in the United Kingdom or Europe, and followed for at least one year after treatment. The primary outcome measure was death or dependency (modified Rankin Scale of 3 to 6) at one year, but the rates of rebleeding and seizures after treatment were also measured and compared. Baseline characteristics at enrollment were similar between treatment groups and, overall, 88% of patients were in good clinical grade (WFNS 1 or 2), 95% of the aneurysms were in the anterior circulation, and 90% were smaller than 10 mm. Patients were not randomized if the treating physicians felt that aneurysm anatomy mandated a specific form of treatment.

After one year of follow-up, 250 (23.5%) of 1063 patients randomized to endovascular treatment were dead or dependent, compared with 326 (30.9%) of 1055 patients randomized to neurosurgical clipping, an absolute risk reduction of 7.4% (95%, CI 3.6-11.2, P = 0.0001). With a mean follow-up of 4 years for all patients, the survival advantage for endovascular treatment was maintained. In the endovascular group, the risk of seizures was significantly lower, but the long-term rate of re-bleeding was higher.


The technology and expertise surrounding endovascular treatment for intracranial aneurysms has improved dramatically, and the ISAT study clearly demonstrates that the one year outcome is better for those patients that have a good clinical grade with small aneurysms in the anterior circulation. Many patients were excluded from randomization because treating physicians felt that one type of treatment was preferred. Elderly patients, very young patients, those with a poor clinical grade, and those with large aneurysms (greater than 10 mm.) or posterior circulation aneurysms were mostly treated outside of the study. Therefore, the ISAT provides guidance for a subset of patients with aneurysmal subarachnoid hemorrhage. In addition, although the mean follow-up is 4 years, we still do not have meaningful data about the long-term (greater than 10 years) results of endovascular treatment. Only 92.6% of endovascular procedures were completed, and only 66% showed complete aneurysm occlusion on follow-up angiography. What will happen to those patients who have partial occlusion of their aneurysm?

The reduction in risk of seizures in the endovascular group is an important observation, and we look forward to more information about this finding in future publications, as well as a comparative study of the long-term cognitive impairments in these patients.

Finally, we must never forget that even in this middle-aged, good clinical grade, small aneurysm population, the overall rate of death and disability at one year still exceeds 25%. There is still much to be done in addition to clipping and coiling of aneurysms if we are to make a significant impact on the natural history of this devastating disease.