Abstract
We report 28 cases of bilateral symmetrical aneurysms, which comprise 6.5% of all aneurysms found in our clinic between April 1979 and March 1990, and compare their features with those of the previous reports. The most common locations are the internal carotid artery (57%) and the middle cerebral artery (36%). Bilaterally symmetrical internal carotid artery aneurysms are much more common in women, with the female to male ratio of 15 : 1. Five to 10% of aneurysms at the internal carotid artery, middle cerebral artery or the distal anterior cerebral artery are bilaterally symmetrical. Based on the focal signs, laterality of subarachnoid hemorrhage found on CT, and angiographic size and shape of the aneurysm (including irregularity of its contour), we could accurately predict the side of the ruptured aneurysms in 92.3% of cases. It has been reported that both ruptured and non-ruptured aneurysms should be treated in one-stage. In our series, however, most cases were treated by two-stage operations without any adverse effects.
