The variations of vertebrobasilar system

SUMMARYVertebrobasilar system (VBS) is an important structure which supplies blood tothe posterior parts of the brain stem, spinal cord, cerebellum and cerebrum. Manykinds anomalies are seen in VBS like all the other vessels. Clinicians must considerthe possibility of variations while making diagnosis or giving treatment. The aim ofour study was to demonstrate the possible variations of VBS in Turkish populationand to discuss these comparing with the literature. VBS which were taken from 109forensic autopsies and 1 cadaver in Afyonkarahisar ve Istanbul regions were studiedand photographed. The width of Vertebral artery (VA) and Basilar artery (BA) wasmeasured; dominancy and hypoplastic arteries and also the types of variations andtheir sites were determined. Proportional correlations were established.In 21.2% of the cases left VA, in 17.3% of cases right VA was dominant.Hypoplastic VA was observed as 20.2% in the right, 14.4% in the left and 4.8%bilaterally. Vertebrobasilar junction (VBJ) was found be at the level of sulcus bulbo-pontinus (20%), below the sulcus (67%) and above the sulcus (12%). BA variationswere the duplication of the proximal segment (0.9%) and the duplication of the distalsegment (1.8%). Anterior spinal arteries (ASA) were originating as a single trunk in12.5% of the cases and it was arising from a transverse anastomosis connectingVA?ies in 6.3% of the cases. Futhermore 15.6% of the ASA were double. In 3.6% ofthe cases left superior cerebellar artery (SCA), in 7.2% of cases right SCA wasdominant. The variations of SCA were early bifurcation (7.2% in the right, 12.7% inthe left), fenestration (4.5% in the right, 7.2% in the left), duplication (14.5% in theright, 12.7% in the left), origin as a common trunk (6.3% in the right, 10% in theleft). In 20% of the cases left posterior cerebral artery (PCA), in 15.4% of cases rightPCA was dominant. Futhermore many atheroma plaques were observed in variousarteries especially in older cases. The incidence was found to be 30% in BA.Our results show that a high percentage of variations can be seen even in asmall number of cases. We believe that our data are clinically important becausevariations are a factor which increases the incidence of aneurysm and thrombus. Wealso think our results will contribute to the demography our country and to clinicalmedicine.Key Words: Vertebrobasilar system, Variation.