Screening of unruptured cerebral aneurysms by computed angiotomography

In thirteen cases, computed angiotomography of the anterior-communicating-artery (AComA) aneurysm site was analyzed in comparison with plain CT and conventional arteriography. Some diagnostic problems were discussed in the screening of unruptured AComA aneurysms by means of computed angiotomography. Nine cases were true-positive, two were false-positive, and the remaining two were false-negative. Three AComA aneurysms, 6, 7, and 9 mm in diameter, appeared as round, cisternal defects at the anterior interhemispheric cistern. Precise interpretation is required for the screening of AComA aneurysms in cases with unilateral hyperplasia (dominance) of the A1 segment; this was found in seven out of the nine true-positive cases. A highdensity mass or nodule pointed toward the opposite side, away from the dominant A1 segment, and also the linear visualization of the uni- or bilateral A2 segments were the characteristic findings of the AComA aneurysms. A loop of the ascending A2 segment was shown to be a false-positive finding; coronal computed angiotomography may permit its differentiation. An AComA aneurysm 3 mm in diameter may represent the potential limit in the screening by computed angiotomography, as was shown in the false-negative cases. (author)