We attempted to determine whether or not there is a relationship between the rate of aneurysmal growth during the waiting period in cases of delayed surgery and the incidence of fatal rebleeding. Angiographic studies were repeated in 53 patients with ruptured aneurysms, with the interval between angiograms ranging from 4 to 60 days. Aneurysmal enlargement over a longer period than 2 months was not evaluated in this study because the prognostic significance of long-term aneurysmal growth is

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... rent from that of short-term growth. Of 53 patients, 40 showed no change in the size of the aneurysm, four showed a decrease, and nine showed an increase. Patients with aneurysmal enlarge ment were classified into two groups: 1) the aneurysmal dome increased in size (4 cases), and 2) only the bleb enlarged (5 cases). All patients in group I suffered from fatal rebleeding during hospitaliza tion, one patient during angiography and one just before craniotomy. Among the patients in group 2, all of the aneurysms were successfully clipped before fatal rebleeding. Short-term growth of aneurysms, as evidenced by angiograms, appears to be extremely hazardous and of significant value in predicting acute, fatal rebleeding. Selected case histories are presented.