Variations in the intracranial vertebrobasilar system

The aim of our study was to demonstrate some possible variations in the vertebrobasilar system (VBS) in the Turkish population and to compare our results with the literature.

The VBS samples were taken from 109 fresh forensic autopsies and one anatomic cadaver. The widths of the vertebral artery (VA), the basilar artery (BA) and their branches were measured; dominancy and hypoplastic arteries, as well as the types of variations and their locations, were determined.

Hypoplastic VA was observed at rates of 20.2% on the right, 14.4% on the left and 4.8% bilaterally. The vertebrobasilar junction was found to be either at the level of bulbopontine sulcus (20%), below the sulcus (67%) or above the sulcus (12%). BA variations were observed as duplications of the proximal (0.9%) and distal segments (1.8%). Anterior spinal artery (ASA) originated as a single trunk in 12.5% of the cases. ASA arose from a transverse anastomosis connecting VAs in 6.3% of the cases. Furthermore, 15.6% of ASAs were double. The observed variations in the superior cerebellar artery were early bifurcation (7.2% on the right, 12.7% on the left), fenestration (4.5% on the right, 7.2% on the left), duplication (14.5% on the right, 12.7% on the left) and origin as a common trunk (6.3% on the right, 10% on the left).

Our results show that a high percentage of variations can be seen even in a small number of cases. We believe that our data are clinically important because, for example, variations are a factor which increases the incidence of aneurism and thrombus. We also think our results will contribute to the demography of our country and to clinical medicine.