title: Real-time ultrasound measurements of changes in suboccipital vertebral artery diameter and blood flow velocity associated with cervical spine rotation.
abstract: OBJECTIVE
  The vulnerability of the vertebral artery (VA) to distortion with sustained, full-range cervical spine rotation, resulting in compromised blood flow and possible vertebrobasilar ischaemia, is well recognized. However, few studies have measured such blood flow changes in the parts of the VA downstream from the region of maximum cervical spine rotation: the suboccipital (VA3) and intracranial vertebral arteries. The purpose of this experimental study was to visualize the VA3 and record the changes in its blood flow associated with cervical spine rotation.
  
  
  METHODS
  VA3 diameters and blood flow velocities were measured in the neutral cervical spine position and with active full-range rotation to the left and right, in 35 healthy female subjects, using colour-coded real-time ultrasound.
  
  
  RESULTS
  Both left and right VA3 diameters and blood flow velocities decreased significantly on ipsilateral rotation. These values increased non-significantly in the left VA3 and decreased non-significantly in the right VA3 on contralateral rotation.
  
  
  CONCLUSIONS
  The results of this study suggest that the distortion or compression of VA3 demonstrated by the reduction in diameter on ipsilateral cervical spine rotation, particularly, was sufficient to result in compromised blood flow. A significant stretching effect of VA3, on contralateral rotation, was not demonstrated in these subjects. Nevertheless, these findings add evidence to support the recommendation that sustained, full-range cervical spine rotation should be avoided in professional practice.
authors.affiliation: Department of Zoology & Physiology, School of Biological Sciences, and Adjunct Clinical Faculty, Department of Kinesiology & Health, Division of Health Sciences, University of Wyoming, Laramie, WY, USA. jeanette_research@hotmail.com
authors.forename: Jeanette
authors.initials: J
authors.lastname: Mitchell
authors.forename: Kristin
authors.initials: K
authors.lastname: Kramschuster
mesh_terms: D001783:Blood Flow Velocity; D002574:Cervical Vertebrae / Q000502:physiology*; D006801:Humans; D012399:Rotation; D014463:Ultrasonography; D014711:Vertebral Artery / Q000000981:diagnostic imaging* / Q000502:physiology*