• Most studies suggest that the risk of aneurysm rupture significantly increases after the size of 7 mm.

• The risk of rupture is greater for posterior circulation aneurysms.

• Five-year risk of aneurysmal rupture based on size (for anterior and posterior circulation aneurysms, respectively):
  
  ---  7 to 12 mm --> 2.6 and 14.5%              

             ---- 13 to 24 mm --> 14.5 and 18.4%