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Variability of the vertebral artery origin and transverse foramen entrance level - CT angiographic study.

BACKGROUND
Vertebral artery (VA), the main element of the posterior brain circulation, has many anatomical variations which generally were widely investigated. However, available data vary in wide ranges, reflecting very different sample sizes, lack of data about left-right or sex differences, and about possible ethnic, regionally specific or genetic differences.


MATERIALS AND METHODS
Certain new findings suggest possible involvement of some environmental factors in VA variations. Accurate anatomical data about VA variations in different regions of the world, including Balkans countries, are still lacking. Therefore we investigated morphological variability of VA origin and its entrance level into cervical transverse foramina in population of Republika Srpska (Bosnia and Herzegovina), including data about the sex and side.


RESULTS
Anatomy of VA was investigated in 112 persons (224 arteries) of both sexes (58 males, 54 females; age 19-83 years), using 64-slice computed tomography (CT) scanner. Origin of VA from subclavian artery (SCA) we found in 95.08% of arteries (52 males, 49 females). Only in 1 (0.45%) male left VA and left SCA had an specific origin from aortic arch (AA), which we named as an "common area of origin". All other observed variations in origin were only of left VA, originating from AA in 4.47% (5 males, 5 females). Left VA most often (usual) entrance level into transverse foramen we found at C6 (87.5%), followed by C5 (8.93%), C4 (3.12%), and in 1 case at level C7 (0.45%). Entry levels at C5, both on right and on the left side, were three times more frequent in males than in females.


CONCLUSIONS
Wide ranges of differences between the data we obtained on a sample in Republika Srpska (Bosnia and Herzegovina) and the data from many other studies require further and wider investigations.