Vertebral arteries ("the verts")

The Vertebral arteries are blood vessels which course through small holes in the cervical vertebral bodies.  These holes are called transverse foramina and are usually seen in the first to the sixth cervical vertebral bodies.  The vertebral arteries take a complex course at the Craniocervical junction where they course laterally though the Axis (Second cervical vertebral body) and then pass through the transverse foramina of the Atlas (First cervical vertebral body) which are widely spaced.  The Vertebral arteries then course posteriorly then medially over the lateral edges of C1 (Atlas, First cervical vertebral body) and pass through the dura mater into the subarachnoid space.  The vertebral arteries give off an important branching artery, the Posterior inferior cerebellar artery (PICA) before joining to form the Basilar artery which is an important artery feeding the brainstem and posterior parts of the brain.  Interruption of bloodflow in the basilar artery can result in coma or death.  Most people can live with only one vertebral artery since adequate blood supply to the basilar artery can be achieved from only one vertebral artery in 95% of people.  If one vertebral artery is injured, the other will be sufficient to supply the basilar artery .  Injury to both vertebral arteries has to occur before serious injury happens due to this natural redundancy, however, in 5% of people, only one vertebral artery ends in the basilar artery (usually the left) and the other vertebral artery ends in the posterior inferior cerebellar artery (PICA).  obviously, injury to the sole vertebral artery ending in the basilar artery may result in coma or death in these patients.