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J R Soc Med. 2004 March; 97(3): 156.
PMCID: PMC1079342

Intracranial aneurysm surgery and its future

Mr Maurice-Williams and Mr Lafuente (November 2003 JRSM1) must be congratulated for their erudite account of issues arising during the senior author's long and august career in neurovascular surgery. However, in the wake of the International Subarachnoid Aneurysm Trial (ISAT2) we believe their views regarding the future mode of treatment of intracranial aneurysms to be somewhat ill-founded.

The dilemma being considered is whether endovascular `coiling' or neurosurgical `clipping' of ruptured cerebral aneurysms is better for excluding the aneurysm sac from circulation. ISAT focuses on a specific subgroup of ruptured aneurysms believed by clinicians to be suitable for either mode of treatment but where there is uncertainty/equipoise as to which line of treatment should be performed. Out of a total 9559 patients presenting with aneurysmal subarachnoid haemorrhage who were considered for the trial, only 2143 (22.5%) fell into this subgroup and were randomized. Of these, the results of 1594 (17% of the original total) were analysed at one year. The major outcome criterion was the risk of dependence or death at one year post treatment. The results show that 30.6% of those treated operatively and 23.7% of those treated endovascularly had poor outcomes—a 6.9% absolute risk reduction. There was no difference in mortality. Of the excluded patients, 3615 underwent clipping, 2737 underwent coiling and 1064 had an unknown management. ISAT did not follow up these patients. Conclusions from the trial data are not universally accepted. Some commentators have argued that the reported results can be entirely explained by a difference in experience of the doctors treating each group.3 It is likely that many surgical procedures were performed by non-specialist surgeons or by trainees.

The risk of requiring a second procedure (surgical or radiological) on the same aneurysm was found to be over four times higher in the group treated by the endovascular technique. 17% (136/801) of those treated endovascularly and 4% (34/793) of those treated surgically underwent further intervention. Of those coiled, 7% (55/801) required further intervention more than a month after initial treatment, compared with 0.8% (6/793) of those who underwent clipping. Whereas clipping is considered a definitive treatment for ruptured aneurysms these data suggest that endovascular management is associated with a higher rate of re-treatment and hence late complications. To this should be added the morbidity associated with the inevitable follow-up cerebral angiography in those treated with coiling. The natural history of a coiled aneurysm is still unknown and, since this cohort of patients is still under follow-up, further results are awaited.

Endovascular embolization has been validated by ISAT to be a front-line treatment for non-complex anterior-circulation aneurysms providing its availability is equivalent to that of the traditional surgical techniques. Further analysis of long-term outcomes is awaited. The ISAT results cannot be extrapolated to the large majority of ruptured aneurysms that are routinely managed by either clipping or coiling in which there is no management uncertainty (and which would therefore be excluded from the trial). ISAT has not demonstrated that coiling is the best treatment for all or even a majority of ruptured cerebral aneurysms presenting to neurosurgeons in the UK.


1. Maurice-Williams RS, Lafuente J. Intracranial aneurysm surgery and its future. J R Soc Med 2001;96: 540–3 [PMC free article] [PubMed]
2. International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial. Lancet 2002;360: 1267–74 [PubMed]
3. Harbaugh RE, Heros RC, Hadley MN. Position Statement on the International Subarachnoid Aneurysm Trial (ISAT). []

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