The significance of unruptured intracranial saccular aneurysms

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✓ The authors report the results of a long-term follow-up study of 130 patients with 161 unruptured intracranial saccular aneurysms. Their findings suggest that unruptured saccular aneurysms less than 10 mm in diameter have a very low probability of subsequent rupture; The mean diameter of the aneurysms that subsequently ruptured was 21.3 mm, compared with a diameter of 7.5 mm for aneurysms defined after rupture at the same institution. Part of the explanation for this discrepancy may be that the size of the filling compartment of the aneurysm decreases after rupture. There is also evidence from the present study that intracranial saccular aneurysms develop with increasing age of the patient and stabilize over a relatively short period, if they do not initially rupture, and that the likelihood of subsequent rupture decreases considerably if the initial stabilized size is less than 10 mm in diameter. Consequently, the critical size for aneurysm rupture is likely to be smaller if rupture occurs at the time of or soon after aneurysm formation. There seems to be a substantial difference in potential for growth and rupture between previously ruptured and unruptured aneurysms.

Article Information

Address reprint requests to: David O. Wiebers, M.D., Mayo Clinic, 200 First Street S.W., Rochester, Minnesota 55905.

© AANS, except where prohibited by US copyright law.

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Figures

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    Graphs showing the survival rates over 7 years in patients with unruptured aneurysms. Upper: Percent of patients who survived without subarachnoid hemorrhage (SAH), and whose largest aneurysm was ≥ 10 mm, correlated with age. Twenty-four patients were < 59 years old and 25 were ≥ 59 years old. Center: Percent of patients who survived in the entire group of 130 patients, compared to the expected survival rate of an age- and sex-matched population derived from the Minnesota Life Tables. Lower: Percent of patients who survived in the entire group of 130 patients correlated with size of the aneurysm.

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    Graphs showing the correlation between size of the aneurysm in the 130 patients in this series with the mean arterial blood pressure (MAP) (left) and the age of the patients (right).

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