[Pitfalls of three-dimensional computed tomographic angiography as an examination for cerebral aneurysm surgery].

Three-dimensional computed tomography (3D-CT) has recently become available and is being increasingly applied in the field of neuroradiology. One of the procedures, 3D-CT angiography (3D-CTA), has been reported to be more advantageous aneurysms. Some investigators insist that conventional angiography is no longer needed to make the diagnosis. We recently experienced cases in which we were misled or found it difficult to judge the relationship between the aneurysm and surrounding structures by 3D-CTA. Our findings can be summed up as follows: 1) two aneurysms in contact with each other could not be opacified separately, 2) the perforators were hardly opacified at all making it impossible to judge the relationship between the aneurysms and these vessels, an assessment which is very important for delicate operations, 3) the origin of A2 was not clearly opacified as being separate from that another near by aneurysm, 4)part of the severely tortuous middle cerebral artery was interpreted as an aneurysm shadow, 5) even M2 is sometimes not well opacified. In conclusion, 3D-CTA itself is not always a satisfactory method of evaluating the relationship between a cerebral aneurysm and its surrounding vessels. Misleading findings should be kept in mind during direct observation at surgery.