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Vertebral artery blood flow

For the past several decades, one consistent question that is yet to be completely answered could be stated as; what is the potential risk of vertebral artery damage during upper cervical manipulation?

Here is some of what we know:

• Vertebral artery damage can lead to cerebrovascular accidents.(1)
• The portion of the vertebral artery located above the Axis and below where it enters the upper vertebral canal is likely the region most susceptible to mechanical insult.(2)
• Adverse events following cervical manipulation are relatively common, but most are mild and benign.(3)
• The estimated risk of serious complications from cervical spine manipulation is 6 per 10,000,000.(4)
• There is no conclusive relationship between vertebrobasilar or carotid artery induced stroke, though a small association cannot be ruled out.(5;6)
• The estimated risk of vertebrobasilar artery stroke following cervical spine manipulation is essentially the same or lower than following a visit to a primary care practitioner.(7;8)
• Strains on the vertebral arteries are much smaller during cervical spine manipulation than failure strains or those produced during range of motion testing.(9)

Adding to the knowledge base, a recent study conducted by Erhardt and colleagues measured vertebral artery blood flow in participants who received a supine high-velocity spinal manipulation to the atlanto-axial region.(10) This randomized controlled trial included a total of 23 participants, of which 12 received the manipulation and 11 were instead held in a pre-manipulative position. Doppler ultrasound was used to measure blood flow characteristics in neutral, pre manipulative, and immediately post manipulative neutral positions. Results demonstrated that neither the manipulation, nor the control position affected blood flow in the vertebral arteries.

Every study has limitations and Erhardt et al., is no exception. We must be careful not to attribute the results from this study to all patients, such as those with pre-existing arterial disease or those with abnormal artery formation because patients with those conditions were not studied. Nevertheless, findings suggests that for most people, a supine high-velocity thrust type manipulation does not adversely affect blood flow in the vertebral arteries. These findings are consistent with those of Herzog, who found no abnormal strains on vertebral arteries in cadaveric specimens while studying the same procedure.(9)

Reference List
(1) Schievink WI, Mokri B, O’Fallon WM. Recurrent spontaneous cervical-artery dissection. N Engl J Med 1994 Feb 10;330(6):393-7.
(2) Kuether TA, Nesbit GM, Clark WM, Barnwell SL. Rotational vertebral artery occlusion: a mechanism of vertebrobasilar insufficiency. Neurosurgery 1997 Aug;41(2):427-32.
(3) Carlesso LC, Gross AR, Santaguida PL, Burnie S, Voth S, Sadi J. Adverse events associated with the use of cervical manipulation and mobilization for the treatment of neck pain in adults: a systematic review. Man Ther 2010 Oct;15(5):434-44.
(4) Hurwitz EL, Aker PD, Adams AH, Meeker WC, Shekelle PG. Manipulation and mobilization of the cervical spine. A systematic review of the literature. Spine (Phila Pa 1976 ) 1996 Aug 1;21(15):1746-59.
(5) Chung CL, Cote P, Stern P, L’esperance G. The Association Between Cervical Spine Manipulation and Carotid Artery Dissection: A Systematic Review of the Literature. J Manipulative Physiol Ther 2014 Jan 3.
(6) Haynes MJ, Vincent K, Fischhoff C, Bremner AP, Lanlo O, Hankey GJ. Assessing the risk of stroke from neck manipulation: a systematic review. Int J Clin Pract 2012 Oct;66(10):940-7.
(7) Cassidy JD, Boyle E, Cote P, He Y, Hogg-Johnson S, Silver FL, et al. Risk of vertebrobasilar stroke and chiropractic care: results of a population-based case-control and case-crossover study. Spine 2008 Feb 15;33(4 Suppl):S176-S183.
(8) Whedon JM, Song Y, Mackenzie TA, Phillips RB, Lukovits TG, Lurie JD. Risk of Stroke After Chiropractic Spinal Manipulation in Medicare B Beneficiaries Aged 66 to 99 Years With Neck Pain. J Manipulative Physiol Ther 2015 Jan 14.
(9) Herzog W, Leonard TR, Symons B, Tang C, Wuest S. Vertebral artery strains during high-speed, low amplitude cervical spinal manipulation. J Electromyogr Kinesiol 2012 Apr 5.
(10) Erhardt JW, Windsor BA, Kerry R, Hoekstra C, Powell DW, Porter-Hoke A, et al. The immediate effect of atlanto-axial high velocity thrust techniques on blood flow in the vertebral artery: A randomized controlled trial. Man Ther 2015 Mar 2.

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