Small, Asymptomatic, Unruptured Intracranial Aneurysm Found by three-dimensional CT Angiography

Many asymptomatic, unruptured intracranial aneurysms (UIAs) are found by MR angiography or CT angiography during the physical checkup. The International Study of Unruptured Intracranial Aneurysms (ISUIA) emphasize that among patients with unruptured aneurysms and no history of subarachnoid hemorrhage, aneurismal size at the time of discovery is the most important variable determining the risk of future rupture. We use three-dimensional CT angiography (3-D CTA) to measure the size and morphological characteristics of the aneurysm, according to the standards of ISUIA. Twenty two UIAs were found in 20 patients; 8 aneurysms were smaller than 2 mm, 2 aneurysms were 2 mm and no one was larger than 6mm. The sizes of all UIAs were rechecked by both volume rendering 3-D CTA and post-contrast 2-D reformatted CT images; the measured diameter is almost the same by both methods. We find 3-D CTA has a good quality to measure the size and morphological characteristics of the aneurysm, even in aneurysm smaller than 2 mm.