Anatomical study of the vertebral artery in Japanese adults.

The aim of the present study was to examine the vertebral arteries. The origins of the right and left vertebral arteries and their entrance points into the cervical transverse foramen were examined in dissections of 515 Japanese cadavers (303 males, 212 females) at Kurume University School of Medicine from 1990 to 2003. There were 515 right vertebral arteries and 514 left vertebral arteries. The right vertebral artery originated from the right subclavian artery in 514 of 515 arteries and one of the arteries arose from the bifurcation of the brachiocephalic trunk. The mean distance between the origin of the right subclavian artery and the right vertebral artery was 20.9 mm. The left vertebral artery originated from the left subclavian artery in 484 of 514 arteries and the mean distance between the origin of the left subclavian artery and the left vertebral artery was 32.1 mm. The remaining 30 arteries (5.8%) originated from the aortic arch between the left common carotid artery and the left subclavian artery and this frequency is similar to previously published data. There was no right-left difference for the entrance point of the vertebral arteries into the cervical transverse foramen and the 6th cervical vertebra (C6) was the most common entrance point. Seventy-eight percent of our cases had right and left vertebral arteries that originated in the subclavian arteries and entered the cervical transverse foramen at C6. Among the 30 left vertebral arteries that originated from the aortic arch, 20 arteries (66.7%) entered a cervical transverse foramen at a level higher than C6. This frequency was higher than that for the left vertebral artery that originated from the subclavian artery.