Differences between left and right suboccipital and intracranial vertebral artery dimensions: an influence on blood flow to the hindbrain?

BACKGROUND AND PURPOSE

Although vertebral artery (VA) blood flow is adequate in normal circumstances, reduction in the dimensions of the vessel because of atherosclerosis, or compression or stretching, may lead to hindbrain hypoxia with serious clinical manifestations. Such effects may be more pronounced in VAs that are naturally smaller than the norm. Because normative data for the suboccipital (VA3) and intracranial (VA4) vertebral artery are not readily available, it was the aim of the present study to measure the dimensions of these distal parts of the VA, to inform professional practice of the possible influence of different vessel dimensions on blood flow to the hindbrain.

METHOD

The study was a laboratory-based observational or descriptive study. A total of 40 and 54 left and right, suboccipital and intracranial parts of the VA (n = 188 vessels), obtained from cadavers of females and males aged 20-80 years, was processed for light microscopic study and measurement of the dimensions of the vessels. The left and right inner and outer diameters, cross-sectional areas and the tunica media thicknesses were calculated in each part of the vessel and compared by use of t-tests.

RESULTS

The histological structure of the VA was typical of a muscular or distributing artery. Although, in the total number of specimens, no statistically significant differences were found between left and right sides in either part of the vessel, a larger left than right VA4 was demonstrated in the females. The VA3 was significantly larger than VA4 in males and females, and all dimensions in both parts of the vessel were greatest in the older age group.

CONCLUSIONS

Reduced VA blood flow, whether because of atherosclerosis or compression or stretching of the vessel, is more likely to occur in arteries that are smaller than normal. This information is of value to clinicians in avoiding further compromising the VA and its blood flow during professional practice.