Studies that compared coil embolisation with microsurgical clipping in patients with intracranial aneurysms (ruptured and unruptured) were eligible for inclusion in the review. Eligible studies designs were randomised controlled trials (RCTs), controlled trials, clinical trials, observational studies, cohort studies, cases series, and case reports. Studies assessing coil embolisation alone or microsurgical clipping alone were excluded. Studies were not excluded on the basis of year of assessment, despite technical differences in endovascular coiling since 1991.
Primary outcome measures were rate of occlusion, aneurysmal re-rupture, functional status (measured using the Glasgow Outcome Scale or Rankin Score), and mortality. Secondary outcomes included procedural failure and morbidity (short-term and long-term).
The included studies used different approaches for craniotomy including suboccipital, pterional modified orbitozygomatic, retrosigmoid, subtemporal and combined transmastoid-retrolabyrinthine with lateral suboccipital. The Guglielmi detachable coil system was the most frequently used endovascular coiling system. Approximately 10% of the studies reported the use of or requirement for intraoperative angiography for microsurgical clipping. Most of the studies (60%) did not report the failure rate for therapy but, where data were reported, the majority of failures were associated with coiling versus surgical failures. Crossover to the other technique was reported in some cases, most commonly crossover from coiling to microsurgical clipping.
Where reported, included participants had aneurysms mainly in the anterior circulation (84.4%) and the remainder were in the posterior circulation (definitions of anterior and posterior were reported in the review). The minimum age of included participants ranged from nine to 51.5 years; the maximum age ranged from 47 to 89 years. Where reported, the mean age of patients undergoing microsurgical clipping was 50.8 years; for those undergoing coil embolisation the mean age was 53 years. Where sufficient data were reported regarding patient gender, 27.7% of participants were male
The authors did not state how papers were selected for review.