An increasing number of cases of incidental cerebral aneurysms are currently being reported. However, the indications for surgery of unruptured asymptomatic cerebral aneurysms are still unclear. The benefit of treatment ultimately depends on the relative risk of subsequent aneurysm rupture in untreated patients versus the risk involved in surgery. We report a series of 90 cases of unruptured aneurysms, admitted and treated over a period of 6 years and 1 month (1993. 12. 1-1999. 12. 31). General

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... information about the natural history of incidentally discovered aneurysms was given to the patients and their relatives. Informed consent was based on the fact that subarachnoid hemorrhage was associated with a poor prognosis, while excellent operative results were common in patients with unruptured aneurysms. Sixty-six patients underwent surgery, and the remaining 24 patients who did not receive surgery were followed up at periods ranging from 1.5 months to 5 years and 9 months. Of the 66 patients who were operated on, there were 11 (17%) cases of postoperative complications, including 5 venous infarctions, 2 memory disturbance, 1 recurrent cerebral infarction, 1 visual disturbance, 1 cerebral embolism and 1 intraoperative rupture. Three patients (4.5%) did not recover. The remaining 8 patients, however, recovered with time or through treatment. Among the 24 patients who were treated conservatively, only 2 developed rupture of the aneurysms (0.4% annual rupture rate) and both made an uneventful recovery. It is our clinical impression, however, that they harbor an unruptured aneurysm with at least mild trepidation. Aneurysm size, location, and number were risk predictors for surgical morbidity in patients with unruptured aneurysms. This experience suggests that if intact aneurysms are treated surgically, careful preoperative evaluation and precise microsurgical techniques are essential. An endovascular approach or some skull base surgical techniques should be considered to obtain better results.