[Subarachnoid hemorrhage due to aneurysm. Natural history].

The natural history represents a basic reference point for evaluating temporal profile of a disease as well as the effect of the employed therapy. The incidence and the risk factors of the subarachnoid hemorrhage due to single aneurysm are presented. In particular the survival rate and mortality are evaluated in conservative treated group versus radical surgery group. The most relevant factors that affect survival are: time and clinical grades of severity. The best chance of alternating overall mortality from subarachnoid hemorrhage due to aneurysm seems to be: surgery within 1-2 days or secondary prevention.