Three-dimensional ct angiography for planning skull base approaches to vertebrobasilar aneurysms: a radiographic and cadaveric study

Three-dimensional CTA was evaluated as a means of acquiring detailed anatomic measurements of the relationships between bony landmarks at the base of the skull and the vertebrobasilar system. Thirty normal patients underwent CT angiography with 1-mm slices reconstructed into dynamic 3D images. Particular attention was paid to the heights and distances between the clivus. the petrous apex, and the vertebrobasilar system. Usefulness of these measurements was then evaluated in 10 cadaveric dissections. Considerable assymetries in the heights of the left versus the right posterior clinoid processes were identifed. in some cases more than a centimeter (mean difference in height, 2.7 mm; range. 0.2-11 mm). Location of the vertebrobasilar system was also extremely variable, as were the angles required for clip placement. 3-D CTA is a safe and reliable tool for appreciating critical anatomic relationships and represents an indispensable adjunct to conventional angiography when planning individualized skull base approaches to the vertebrobasilar system.