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Safety and occlusion rates of surgical treatment of unruptured intracranial aneurysms: a systematic review and meta-analysis of the literature from 1990 to 2011
  1. Marc Kotowski1,2,
  2. Olivier Naggara3,
  3. Tim E Darsaut1,4,5,
  4. Suzanne Nolet5,
  5. Guylaine Gevry5,
  6. Evgueni Kouznetsov1,
  7. Jean Raymond1,5
  1. 1Department of Radiology, Centre hospitalier de l'Université de Montréal (CHUM), Notre-Dame Hospital, Montreal, Canada
  2. 2Department of Neurosurgery, Centre hospitalier universitaire Vaudois, Lausanne, Switzerland
  3. 3Département d'Imagerie Morphologique and Fonctionnelle, Université Paris Descartes, Sorbonne Paris Cité, INSERM UMR 894, Hôpital Sainte-Anne, Paris, France
  4. 4Mackenzie Health Sciences Centre, Division of Neurosurgery, Department of Surgery, University of Alberta Hospital, Edmonton, Alberta, Canada
  5. 5CHUM Research Centre, Interventional Neuroradiology Laboratory, Notre-Dame Hospital, Montreal, Canada
  1. Correspondence to Dr J Raymond, CHUM Notre-Dame Hospital, Department of Radiology, 1560 Sherbrooke East, Pav Simard, Z12909, Montreal, Canada H2L 4M1; jean.raymond{at}


Background and purpose Surgical clipping of unruptured intracranial aneurysms (UIAs) has recently been challenged by the emergence of endovascular treatment. We performed an updated systematic review and meta-analysis on the surgical treatment of UIAs, in an attempt to determine the aneurysm occlusion rates and safety of surgery in the modern era.

Methods A detailed protocol was developed prior to conducting the review according to the Cochrane Collaboration guidelines. Electronic databases spanning January 1990–April 2011 were searched, complemented by hand searching. Heterogeneity was assessed using I2, and publication bias with funnel plots. Surgical mortality and morbidity were analysed with weighted random effect models.

Results 60 studies with 9845 patients harbouring 10 845 aneurysms were included. Mortality occurred in 157 patients (1.7%; 99% CI 0.9% to 3.0%; I2=82%). Unfavourable outcomes, including death, occurred in 692 patients (6.7%; 99% CI 4.9% to 9.0%; I2=85%). Morbidity rates were significantly greater in higher quality studies, and with large or posterior circulation aneurysms. Reported morbidity rates decreased over time. Studies were generally of poor quality; funnel plots showed heterogeneous results and publication bias, and data on aneurysm occlusion rates were scant.

Conclusions In studies published between 1990 and 2011, clipping of UIAs was associated with 1.7% mortality and 6.7% overall morbidity. The reputed durability of clipping has not been rigorously documented. Due to the quality of the included studies, the available literature cannot properly guide clinical decisions.

  • Neurosurgery
  • Systematic Reviews
  • Meta-Analysis

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