Peggy Nguyen, MD

Murayama Y, Takao H, Ishibashi T, Saguchi T, Ebara M, Yuki I, et al. Risk Analysis of Unruptured Intracranial Aneurysms: Prospective 10-Year Cohort Study. Stroke. 2016

The optimal management of unruptured aneurysms, whether by clipping or coiling, has never been defined in a randomized study.  Inferences can be made from what we know about the natural course of unruptured aneurysms, which have been previously studied in the ISUIA and UCAS. In this study, the authors add to the literature with a 10-year follow up of unruptured aneurysms to define the risk factors of rupture and looked at outcomes of rupture.

A total of 2665 patients with 3434 unruptured intracranial aneurysms (UIAs) were referred to

the institution, of which 1556 patients with 1960 aneurysms were conservatively observed and 937 aneurysms were repaired (793 by coiling, 144 by surgical clipping). In the

conservatively managed group:

  • The mean follow up duration was 7388 aneurysm-years.
  • 56 aneurysms ruptured with an overall annual incidence of subarachnoid hemorrhage of 0.76% with mean duration to rupture from initial consultation being 547 days.
  • Independent risk factors for aneurysm rupture were: (1) aneurysm size, (2) specific location, (3) presence of a daughter sac, and (4) history of SAH.
  • The annual rupture rate of aneurysms < 5 mm was 0.33%, > 5 mm was 3.1%, 7-9 mm was 2.9%, 10-24 mm was 10.2%, and 25+ mm was 33.1%; a cut-off point of 5 mm was associated with a higher risk of rupture, smaller than the 7 mm size which was previously demonstrated.
  • Vertebro-basilar aneurysms demonstrated a significantly higher risk of rupture compared to other locations.
  • Of ruptured aneurysms, only 46.4% patients returned to normal life; 28.6% resulted in an mRS of 3-5, 26.8% resulted in death. 

Given the devastating effects of aneurysm rupture, as confirmed in this study, would it be prudent to coil/clip these aneurysms, even when incidental and unruptured? Unfortunately, this study does not necessarily answer the question of what the best management would be for unruptured aneurysms; it does, however, confirm the size relationship of aneurysm and rupture, at a smaller size than previously reported, which prompts additional questions on what, exactly, is the size of aneurysm which we should be concerned about.