Sex and level differences in the diameters of extradural segment of vertebral artery: computed tomography angiographic study.

Abstract

We investigated diameters of prevertebral - V1, and atlantic - V3 parts of extradural segment of vertebral artery (VA). Variable results from the literaturę about VA diameters reflect variety of diagnostic and imaging methods, various sample sizes, different levels of measurements, and lack of possible specific ethnic, regional or genetic data. Additionally, the data are often without distinctions of left-right or of sex. For this computed tomography (CT) angiographic study 91 adult people (182 VAs) of both sexes (47 males and 44 females) and of age between 33 and 75 years were selected. Diameters were measured at fixed predefined points of VA, marked as inferior (A) point (at V1 part in region of VA origin), as middle (B) point (the end of V1 part), and superior (C) point, at V3 part - 5 mm before VA penetrated the dura. Inferior (A) and middle (B) points actually represent locations at beginning (A) and at terminal (B) regions of V1 part of VA, and superior point C represents terminal part of V3. In total sample ipsilateral (both left [L] and right [R] sided) diameters on investigated levels of VA showed progressive and highly significant decreases. The mean values were on the right side at point A - 3.63 mm, at B point - 3.31 mm, and at C point - 3.08 mm. On the left side, mean values were at point A - 3.76 mm, at B point - 3.50 mm, and at point C - 3.21 mm. Pattern of increasing sex differences in diameters of VA, was ranging from no differences (point A), trough significant (point B), to highly significant differences (point C). For inferior point (A) we did not find significant differences in VA diameters between males (R 3.78 mm; L 3.89 mm) and females (R 3.50 mm; L 3.62 mm), in middle (B) point sex differences were significant (males: R 3.44 mm, L 3.66 mm; females: R 3.18 mm, L 3.33 mm) and in most superior point (C) differences were highly significant (males: R 3.278 mm, L 3.39 mm; females: R 2.88 mm, L 3.01 mm). However, we did not find significant intrasex (in males or in females) left-right differences in mean values of VA diameters for all three investigated levels. Our findings, as the first data about diameters of VA systematically obtained by CT angiography in the population of western Balkans and wider, suggest that in design of future studies of VA diameters is necessary to analyse separately the data for sex, as well as to use defined standard levels.