The earliest randomized prospective study by Koivisto et al. found clinical and angiographic results between the two methodologies to be statistically equivalent. The more recent and larger randomized, prospective study from the International Subarachnoid Aneurysm Trial group suggests that endovascular coiling is statistically superior to microsurgical clipping in clinical outcomes, although the recently published long-term follow-up of International Subarachnoid Aneurysm Trial patients documents higher recurrence and rehemorrhage rates after endovascular coiling. Although there is no clear consensus in these two studies or in the 45 observational studies included, clinically useful information can be extracted to improve shared decision making and interaction between interventionalists and neurosurgeons, create more individualized treatment algorithms, and enhance future research.

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