What is the relevant anatomy in vertebral artery dissection (VAD)?

Updated: Feb 21, 2019
  • Author: Eddy S Lang, MDCM, CCFP(EM), CSPQ; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Answer

An understanding of the anatomy of the vertebral artery is helpful. The course of the vertebral artery usually is divided into four sections as follows:

  • Segment I runs from its takeoff at the first branch of the subclavian artery to the transverse foramina of cervical vertebra C5 or C6.

  • Segment II runs entirely within the transverse foramina of C5/C6 to C2.

  • Segment III, a tortuous segment, begins at the transverse foramen of C2, runs posterolaterally to loop around the posterior arch of C1, and passes subsequently between the atlas and the occiput. This segment is encased in muscles, nerves, and the atlanto-occipital membrane.

  • Segment IV, the intracranial segment, begins as it pierces the dura at the foramen magnum and continues until the junction of the pons and medulla, where the vertebral arteries merge to join the larger proximal basilar trunk.

Spontaneous dissection of the vertebral artery usually occurs in the tortuous distal extracranial segment (segment III) but may extend into the intracranial portion or segment IV.


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