ISAT trial: coiling or clipping for intracranial aneurysms?

To a certain extent, ISAT only confirms data that have already been shown in other studies, with some reservations and revelations. First, of the 9559 patients that were eligible for inclusion, 78% were excluded. 9% of the exclusions were for refusal to participate, and the remaining 69% were excluded from the study because the aneurysm could not be treated by either procedure. Almost all intracranial aneurysms can be treated by surgery and therefore 69% of the aneurysms were excluded because they probably had a configuration not suitable or ideal for coiling. This proportion could be interpreted as representing a selection or sample bias, but in reality represents a known fact that not all aneurysms are suitable for coiling. Consequently, only 31% of aneurysms were suitable for coiling, which is less than in most practices in Europe, USA, and Canada, including my own as a neurosurgeon and interventional neuroradiologist, who does both clipping and coiling. This low number could be partly attributable to the rarity of posterior circulation aneurysms. The rarity of posterior circulation and middle cerebral artery aneurysms also raises the possibility of sample bias in ISAT because a larger number of posterior circulation aneurysms would have favoured coiling,5-7 and a larger number of middle cerebral artery aneurysms would have favoured surgery.8