[Size and location of ruptured cerebral aneurysms diagnosed by three dimensional computed tomographic angiography]

The purpose of this study is to confirm the correct size and the location of ruptured cerebral aneurysms diagnosed and measured using three dimensional computed tomographic angiography. The size and the location were investigated in 136 ruptured cerebral aneurysms encountered in our hospital during 3 years and 10 months. As regards the location of 136 ruptured cerebral aneurysms, 40 were anterior communicating artery aneurysms, 35 were middle cerebral artery aneurysms, 33 were internal carotid artery aneurysms, 12 were distal anterior cerebral artery aneurysms and 16 were posterior circulatory aneurysms. Twenty-seven aneurysms (19.9%) were smaller than 3.0 mm, and 74 aneurysms (54.4%) were less than 5.0 mm in maximum diameter. The maximum diameter of aneurysms located on the anterior communicating artery was 4.8 mm. On the middle cerebral artery it was 6.7 mm, and on the internal carotid artery it was 7.4 mm. We concluded that the rate of small aneurysmal rupture was comparatively more frequent than is reported. The results led to the speculation that the aneurysmal rupture occurred more often in smaller size, and the rate of occurrence may be also related to the aneurysmal location.