Ruptured intracranial aneurysms: an autopsy study of 133 patients.

The autopsy findings of 133 patients with ruptured intracranial aneurysms were reviewed: 24 (18%) had multiple aneurysms. Intraventricular hemorrhage was seen in 53 patients (40%), and intracerebral hematoma was seen in 52 (39%). Intraventricular hemorrhage was seen most frequently in patients with anterior communicating artery aneurysms [21 of 40 (53%)]. Intracerebral hematoma occurred most frequently in patients with middle cerebral artery aneurysms [11 of 28 (39%)]. Hemorrhages arising from anterior communicating artery aneurysms had two types of penetration routes into the lateral ventricle. The first was through the inferomedial portion of the frontal lobe, and the second was through the corpus callosum. The second type was poorly visualized in horizontal sections of the brain. Of 40 patients with anterior communicating artery aneurysms, the first type of penetration route was observed in 15, and the second type was found in 3. The second type is rare, and if the hemorrhage is not massive, it may be overlooked in axial computed tomography scans. Of the 109 ruptured aneurysms, 18 (17%) were 4 mm or less in diameter, 50 (46%) were 5-9 mm in diameter, and 41 (38%) were 10 mm or larger in diameter. In the 21 patients with multiple aneurysms, unruptured aneurysms were smaller than ruptured aneurysms in 17 of 27 (63%), equal size in 9 (33%), and larger in 1 (4%). Regarding rerupture, the larger the ruptured aneurysms were, the higher the percentage of rerupture, that is, 11% of 18 ruptured aneurysms of 4 mm or less in diameter, 32% of 50 of 5-9 mm in diameter, and 37% of 41 of 10 mm or larger in diameter had reruptured. It seems that the larger the size of the aneurysm, the higher the risk of rerupture as well as of initial rupture.