Usefulness of Computed Cerebral Angiotomography for Direct Detection of Intracranial Aneurysms

Usefulness of computed cerebral angiotomography for direct detection of intracranial aneurysms was studied. Among forty-one aneurysms in the series, thirty-one (80.5%) were detected by computed cerebral angiotomography. Detection rates of aneurysms depended on the size, i.e., 56.3% in 16 aneurysms smaller than 5 mm in diameter, 94.7% in 19 between 6 and 10 mm, and 100% in six aneurysms larger than 10 mm. The smallest aneurysm detected by computed cerebral angiotomography was 5×4×4 mm in size on the angiogram. Location of the aneurysms, affected the detection rate as follows: 88.2% in 17 anterior cerebral artery aneurysms (16 anterior communicating artery aneurysms and one A, portion), 77.8% in nine middle cerebral artery aneurysms, 87.5% in eight aneurysms of supraclinoid portion of the internal carotid artery (ICA), 0% in two internal carotid-ophthalmic artery aneurysms, 75 % in four aneurysms of upper half of the basilar artery and 100% in one posterior cerebral artery aneurysm. It seems difficult to detect aneurysms in the infraclinoid portion of ICA. Of 24 patients with subarachnoid hemorrhage, ruptured aneurysms were detected in 22 by computed cerebral angiotomography. Initial CT findings in 64% of these 22 patients showed no evidence of blood or diffuse or symmetrical high density areas in the subarachnoid space. In these patients, computed cerebral angiotomography was useful for topographical diagnosis of the ruptured aneurysm. Incidental asymptomatic aneurysms were detected in nine out of 33 patients in this series. An aneurysm may be suggested by a round or oval isodensity defect in the Sylvian fissure or suprasellar cistern, defect of the edge of the so-called “pentagon” in plain CT and then if its density is highly and homogeneously increased and continuous with the main cerebral arteries on computed cerebral angiotomogram. Computed cerebral angiotomography raised the detection rate of intracranial aneurysms. It was possible to recognize not only aneurysms themselves but also afferent and efferent arteries continuous with aneurysms, the relation between the aneurysm and cistern, parenchymal brain tissue and hematoma surrounding the aneurysm by computed cerebral angiotomography. Nine cases of incidental asymptomatic aneurysms were detected directly by computed cerebral angiotomography. This non-invasive method seems to be useful as a screening procedure to discover non-ruptured asymptomatic aneurysms. There is a possibility that location of an aneurysm can be shown by computed cerebral angiotomography before invasive angiography.