International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2,143 patients with ruptured intracranial aneurysms: a randomised trial.

Molyneux A, Kerr R, Stratton I, Sandercock P, Clarke M, Shrimpton J, Holman R.
Lancet. 2002: 360: 1267-74.

Purpose: Determine whether endovascular treatment compared with neurosurgical treatment reduced the proportion of patients dependent or dead, defined by a modified Rankin score of 3-6

2143 patients randomly assigned endovascular coil treatment (n=1070) or neurosurgical clipping (n=1073). Most randomized patients had good-grade (88 percent in WFNS grades I and II), small anterior circulation aneurysms (92 percent less than 11 mm in size).


Died or had mRS score 3-6 at 1 year

– Relative risk reduction favoring coiling is 22.6%. Absolute risk reduction is 6.9%.*

– The risk of rebleeding during the first year was 2.4 percent for the endovascular group and 1.0 percent for the surgical group. Rebleeding after 1 year was 2 per 1,276 follow-up years for coiling patients and 0 per 1,081 follow-up years for surgical patients.

In ruptured brain aneurysm patients, equally suited for both treatment options, endovascular coil treatment produces substantially better patient outcomes than surgery in terms of survival free of disability at one year.