Direct detection of incidental asymptomatic aneurysm by computed tomography

Incidental asymptomatic aneurysms were found in 9 of 52 patients with intracranial aneurysms from February, 1978 to March, 1980. They had only mild initial symptoms, namely, headache, dysarthria, aphasis, light hemiparesis and others. No patients had severe neurological deficits. In eight of 9 patients with asymptomatic aneurysm, except one case of hypertensive intracerebral hematoma, 9 aneurysms (8 patients) were directly detected by high resolution CT (GE CT/T 8800) and confirmed by angiography. Location of these aneurysms as follows: three at the middle cerebral artery trifurcation, two at the internal carotisposterior communicans junction, one at anterior communication artery, one at the basilar top, one at the basilaris artery-superior cerebelli artery junction and one at the posterior cerebral artery. The smallest aneurysm detected by CT as 5 x 4 x 4 mm in size on angiography. The aneurysm may be suggested by small round or oval defect in the Sylvian fissure or suprasellar cistern, defect of the edge of the so called ''pentagon'' in the plain CT and then if its density is highly and homogeneously increased after contrast-enhanced (CE) scan. As the circle of Willis and other major cerebral arteries can often be demonstrated on CE.CT images, the aneurysm is frequently seen on these cerebral arteries. Limiting factors to direct CT detection of intracranial aneurysms are seemed to be size and location of aneurysm, anatomic location of circle of Willis and motion of patients etc. It may be considered, in our experiences, that the CT is useful in diagnosis of asymptomatic aneurysm and the higher direct CT detection rate to aneurysms, small or medium sized as well as giant aneurysms, will be obtained by devising scanning method, namely, multiprojection scans, multiple overlapping method and improvement of enhanced method. (author)