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Research paper
Surgical clipping or endovascular coiling for unruptured intracranial aneurysms: a pragmatic randomised trial
  1. Tim E Darsaut1,
  2. J Max Findlay1,
  3. Elsa Magro2,
  4. Marc Kotowski3,
  5. Daniel Roy3,
  6. Alain Weill3,
  7. Michel W Bojanowski4,
  8. Chiraz Chaalala4,
  9. Daniela Iancu5,
  10. Howard Lesiuk6,
  11. John Sinclair6,
  12. Felix Scholtes7,
  13. Didier Martin7,
  14. Michael M Chow1,
  15. Cian J O’Kelly1,
  16. John H Wong8,
  17. Ken Butcher9,
  18. Allan J Fox10,
  19. Adam S Arthur11,
  20. Francois Guilbert3,
  21. Lu Tian12,
  22. Miguel Chagnon13,
  23. Suzanne Nolet14,
  24. Guylaine Gevry14,
  25. Jean Raymond3
  1. 1 Department of Surgery, Division of Neurosurgery, University of Alberta, Edmonton, Canada
  2. 2 Service de Neurochirurgie, CHU Cavale Blanche, INSERM UMR 1101 LaTIM, Brest, France
  3. 3 Department of Radiology, Service of Neuroradiology, Centre Hospitalier de l’Université de Montréal (CHUM), Notre-Dame Hospital, Montreal, Canada
  4. 4 Department of Surgery, Service of Neurosurgery, Centre Hospitalier de l’Université de Montréal (CHUM), Notre-Dame Hospital, Montreal, Canada
  5. 5 Department of Medical Imaging, Section of Neuroradiology, University of Ottawa, The Ottawa Hospital, Ottawa, Canada
  6. 6 Department of Surgery, Section of Neurosurgery, University of Ottawa, The Ottawa Hospital, Ottawa, Canada
  7. 7 Department of Neurosurgery, Centre Hospitalier Universitaire de Liège, Liège, Belgium
  8. 8 Division of Neurosurgery, Department of Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Alberta, Canada
  9. 9 Department of Medicine, Division of Neurology, University of Alberta, Edmonton, Canada
  10. 10 Department of Medical Imaging, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada
  11. 11 Department of Neurosurgery, Semmes-Murphey Neurologic and Spine Institute, University of Tennessee, Memphis, USA
  12. 12 Department of Biomedical Data Science, Stanford University School of Medicine, Stanford, California, USA
  13. 13 Department of Mathematics and Statistics, Université de Montréal, Montreal, Canada
  14. 14 Research Centre, Centre Hospitalier de l’Université de Montréal (CHUM), Notre-Dame Hospital, Montreal, Canada
  1. Correspondence to Dr Jean Raymond, CHUM, Notre-Dame Hospital, Department of Radiology 1560, Sherbrooke East, Pavilion Simard, Suite Z12909, Montreal, Quebec H2L 4M1, Canada; jean.raymond{at}


Background Unruptured intracranial aneurysms (UIAs) are increasingly diagnosed and are commonly treated using endovascular treatment or microsurgical clipping. The safety and efficacy of treatments have not been compared in a randomised trial. How to treat patients with UIAs suitable for both options remains unknown.

Methods We randomly allocated clipping or coiling to patients with one or more 3–25 mm UIAs judged treatable both ways. The primary outcome was treatment failure, defined as: initial failure of aneurysm treatment, intracranial haemorrhage or residual aneurysm on 1-year imaging. Secondary outcomes included neurological deficits following treatment, hospitalisation >5 days, overall morbidity and mortality and angiographic results at 1 year.

Results The trial was designed to include 260 patients. An analysis was performed for slow accrual: 136 patients were enrolled from 2010 through 2016 and 134 patients were treated. The 1-year primary outcome, available for 104 patients, was reached in 5/48 (10.4% (4.5%–22.2%)) patients allocated surgical clipping, and 10/56 (17.9% (10.0%–29.8%)) patients allocated endovascular coiling (OR: 0.54 (0.13–1.90), p=0.40). Morbidity and mortality (modified Rankin Scale>2) at 1 year occurred in 2/48 (4.2% (1.2%–14.0%)) and 2/56 (3.6% (1.0%–12.1%)) patients allocated clipping and coiling, respectively. New neurological deficits (15/65 vs 6/69; OR: 3.12 (1.05–10.57), p=0.031), and hospitalisations beyond 5 days (30/65 vs 6/69; OR: 8.85 (3.22–28.59), p=0.0001) were more frequent after clipping.

Conclusion Surgical clipping or endovascular coiling of UIAs did not show differences in morbidity at 1 year. Trial continuation and additional randomised evidence will be necessary to establish the supposed superior efficacy of clipping.

  • unruptured intracranial aneurysm
  • randomized controlled trial
  • pragmatic trial
  • surgical clipping
  • endovascular coiling

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  • Contributors TED, JR and JMF designed the study and wrote the report; MC designed the statistical analysis, which was performed by LT; TED, JR, JMF, EM, MK, DR, AW, MWB, CC, DI, HL, JS, FS, DM, MMC, CJO and JHW recruited patients and collected data; SN and GG collected data and prepared the manuscript, KB, AJF and AA served on the DSMC; FG was leader of the core laboratory.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Comité d'éthique du Centre hospitalier de l'Université de Montréal.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement All available data can be obtained by contacting the corresponding author.