One of the most impressive studies on the outcomes of the two treatments for intracranial aneurysms, the International Subarachnoid Aneurysm Trial (ISAT) was presented in 2002 ¹⁾. It suggested that the ruptured aneurysm treated endovascularly had a better one-year outcome, maintained at seven years, in terms of neurodisability and seizures. An increased risk of delayed rebleeding compared with the aneurysm treated surgically was seen. The practice of radiological follow up to identify the possible recurrence was encouraged, and rates of prophylactic retreatment following endovascular therapy were noted to be higher that for open surgery.

Because the main goal of aneurysm treatment is the prevention of recurrent bleeding, an assessment of treatment effectiveness is essential. In ISAT, the higher risk for aneurysm rebleeding of the coil group in the as-treated analysis was statistically significant. Further comparison of the 2 treatment groups in ISAT’s last report shows that the risk for rebleeding after coiling is 2.5 times higher than after clipping and that the risk for death from an SAH is twice as high after coiling as after clipping ^{2) 3)}.

Since then, increasing number of patients are managed by endovascular technique shifting the anesthetic management outside the operating room

Previous analyses of the International Subarachnoid Aneurysm Trial (ISAT) cohort have reported on the risks of recurrent subarachnoid haemorrhage and death or dependency for a minimum of 5 years and up to a maximum of 14 years after treatment of a ruptured intracranial aneurysm with either neurosurgical clipping or endovascular coiling. At 1 year there was a 7% absolute and a 24% relative risk reduction of death and dependency in the coiling group compared with the clipping group, but the medium-term results showed the increased need for re-treatment of the target aneurysm in the patients given coiling.

The 1-year results of International Subarachnoid Aneurysm Trial (ISAT) showed that for the treatment of ruptured aneurysms, coil embolization was superior to clip occlusion, but most of the trial patients had small aneurysms in the anterior circulation and were in good clinical condition. Therefore, evidence that the 1-year ISAT results apply to all patients with aneurysms or that the ISAT results could be replicated has been lacking. To address the issue of the broader applicability of the ISAT results, the Barrow Ruptured Aneurysm Trial (BRAT) used a prospective intent-to-treat design that randomized all patients admitted with a diagnosis of subarachnoid hemorrhage (SAH). The 1- and 3-year results have been published previously ^{4) 5)}.