accessory vertebral vein

n.
  1. A vein that accompanies the vertebral vein but passes through the foramen of the transverse process of the seventh cervical vertebra and opens independently into the brachiocephalic vein.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.