title: The effect of end-range cervical rotation on vertebral and internal carotid arterial blood flow and cerebral inflow: A sub analysis of an MRI study.
abstract: BACKGROUND
  Cervical spine manual therapy has been associated with a small risk of serious adverse neurovascular events, particularly to the vertebral arteries. Sustained end-range rotation is recommended clinically as a pre-manipulative screening tool; however ultrasound studies have yielded conflicting results about the effect of rotation on blood flow in the vertebral arteries. There has been little research on internal carotid arterial flow or utilising the reference standard of angiography.
  
  
  OBJECTIVE
  To evaluate the mean effect of cervical rotation on blood flow in the craniocervical arteries and blood supply to the brain, as well as individual variation.
  
  
  METHODS
  This was an observational study.
  
  
  METHODS
  Magnetic resonance angiography was used to measure average blood flow volume in the vertebral arteries, internal carotid arteries, and total cerebral inflow, in three neck positions: neutral, end-range left rotation and end-range right rotation in healthy adults.
  
  
  RESULTS
  Twenty participants were evaluated. There was a decrease in average blood flow volume in the vertebral and internal carotid arteries on contralateral rotation, compared to neutral. This was statistically significant on left rotation only. Ipsilateral rotation had no effect on average blood flow volume in any artery. Total cerebral inflow was not significantly affected by rotation in either direction.
  
  
  CONCLUSIONS
  It appears that in healthy adults the cerebral vasculature can compensate for decreased flow in one or more arteries by increasing flow in other arteries, to maintain cerebral perfusion. Sustained end-range rotation may therefore reflect the compensatory capacity of the system as a whole rather than isolated vertebrobasilar function.
authors.affiliation: Discipline of Physiotherapy, School of Health Sciences, Faculty of Health and Medicine, The University of Newcastle, NSW, Australia; School of Health and Rehabilitation Sciences, University of Queensland, St Lucia 4072, QLD, Australia. Electronic address: Lucy.Thomas@newcastle.edu.au.
authors.forename: Lucy C
authors.initials: LC
authors.lastname: Thomas
authors.affiliation: Discipline of Physiotherapy, School of Health Sciences, Faculty of Health and Medicine, The University of Newcastle, NSW, Australia.
authors.forename: Lucy R
authors.initials: LR
authors.lastname: McLeod
authors.affiliation: Discipline of Physiotherapy, School of Health Sciences, Faculty of Health and Medicine, The University of Newcastle, NSW, Australia.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Osmotherly
authors.affiliation: Discipline of Physiotherapy, School of Health Sciences, Faculty of Health and Medicine, The University of Newcastle, NSW, Australia.
authors.forename: Darren A
authors.initials: DA
authors.lastname: Rivett
mesh_terms: D000328:Adult; D001315:Australia; D001783:Blood Flow Velocity; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging / Q000502:physiology*; D002574:Cervical Vertebrae / Q000098:blood supply* / Q000000981:diagnostic imaging; D015331:Cohort Studies; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D020393:Manipulation, Spinal / Q000379:methods*; D008875:Middle Aged; D012016:Reference Values; D012399:Rotation; D014711:Vertebral Artery / Q000000981:diagnostic imaging / Q000502:physiology*; D055815:Young Adult
keywords: Carotid artery; MRI; Neck rotation; Vertebral artery