A report on the scientific literature: verified by a study of 110 Million person-years:
Cervical artery dissection (CAD) is a major source of cervical ischemia in all ages, and can lead to various clinical symptoms such as neck pain, headache, Horner’s Syndrome (paresis of the eye) and cranial nerve palsy. An underlying arteriopathy, which is often genetically encoded, is believed to have a role in the development of CAD. (1) There have been case studies and low-quality published literature that attempt to link chiropractic care and CAD. This type of reporting often reports dogma and as in this case, is devoid of high-quality standards of scientific examination and lacking a complete set of facts. (2) When considering CAD, both the internal carotid and vertebral arteries must be considered. Dissection of one or both can lead to serious complications but can also be asymptomatic. Thrombolytic stroke is typically in the old, while cervical artery dissection causes stroke in young and middle-aged patients. Only 1-2% of ischemic strokes are caused by CAD, but in younger patients, 10-25% are caused by CAD. The overall incidence of CAD is 2.5- 5.0 patients per 100,000; the mean age is 44 years old. CAD is rare beyond 65 years old. (3, 4)
Although headaches, migraine headaches, minor trauma, neck pain, and inflammatory and connective tissue diseases have been thought to play a role in CAD, patients with CAD (with or without trauma) likely have an underlying arteriopathy, an inflammatory process or structural instability of the arteries that lead to dissection. A biopsy-proven study, Cervical Artery Dissections: A Review, conducted by JJ Robertson and A. Koyfman in 2016, shows structural differences in the arterial walls of patients with spontaneous CAD and in patients who have sustained major trauma and a positive association with dissection and kinking and coiling of the internal carotid artery, which suggests an underlying predisposition. (4)
In 2001-2002, the number of visits to medical primary care providers and chiropractors in the US and Canada was 10.2 million. Visits to primary care providers accounted for 80% of the total, while visits to chiropractors accounted for 12%. (5) The most prevalent diagnoses in chiropractic care involve neck and back pain. (5,6) The most common treatment at a chiropractic office is a spinal high-velocity, low-amplitude manipulation, commonly known as a chiropractic spinal adjustment.
A Meta-analysis of 253 articles on chiropractic care and cervical artery dissection by Church, et. Al. (3) showed that neck pain and headaches are found in approximately 80% of CAD patients. Neck pain and headaches are also common symptoms in patients with cervical artery dissection. They concluded: "There is no convincing evidence to support a causal link between chiropractic manipulation and cervical arterial dissection.” which is a correlation, but not causally related. The most prevalent co-founder is neck pain and that demographic typically visits a chiropractor. When you consider the association between chiropractic visits vs. medical primary care visits with patients who experienced a CAD, the utilization was similar, yet because chiropractors treat neck pain there appears to be a dogmatic conclusion that chiropractic is the causative factor for dissection despite the lack of evidence.
The evidence, as determined by Church et. Al. is based upon the Grading Recommendation Assessment Development and Evaluation (GRADE) system of rating quality of evidence and grading strength in systematic reviews. Those reviews ranged from high quality of evidence to very low quality of evidence. (7) Church et. Al. (3) found that the quality of the body of data using the GRADE criteria revealed that it fell within the “very low” category. Also, they found no evidence for a causal link between chiropractic care and CAD. Perhaps the greatest threat to the reliability of any conclusions drawn from these data is that together they describe a correlation but not a causal relationship, and any unmeasured variable is a potential confounder. As previously discussed, the most likely potential confounder in this case is neck pain with no causal evidence.
Cassidy et al. (2008) studied the occurrence of vertebral basilar artery (VBA) stroke events in Ontario, Canada over nine years with a database representing almost 110 million person-years (12.2 million people, studied over 9 years, equals 110 million person-years). (8) The purpose of this study was to investigate if the rates of VBA stroke, which is sometimes caused by CAD, were higher in patients treated by chiropractors than in those treated by medical primary care doctors. The premise was that if the rate of VBA stroke was higher with chiropractic care, then one could logically say there were a cause and effect relationship between chiropractic care and VBA strokes. The results were conclusive: There was no greater likelihood of a patient experiencing a stroke following a visit to his/her chiropractor than there was after a visit to his/her primary care physician. Cassidy et al wrote:
“We found no evidence of excess risk of VBA stroke with associated chiropractic care compared to primary care.” Cassidy et al. concluded that overall, 4% of stroke patients had visited a chiropractor within 30 days of a stroke while 53% of stroke patients had visited their medical primary care providers within the same time frame. The authors suggest that because neck pain is a common symptom of CAD, patients visit their doctors with the onset of symptoms, prior to the development of a full-blown stroke scenario. Because the association between VBA stroke and visits to both chiropractic and medical physicians is the same, there appears to be no increased risk of VBA stroke from chiropractic care. In fact, the incident of chiropractic vs. medical care was substantially lower in certain situations based upon the data. (8)
Cervical artery dissection occurs rarely, yet often creates significant adverse outcomes to patients. Unfortunately, there has been a bias in the medical community, incorrectly linking chiropractic care and CAD. But the evidence is mounting that there is no causal relationship between them. With literature bordering on dogma devoid of the facts in high-quality studies. 12.2 million people study over 9 years equaling 110 million person-years conclude no causal relationship doing chiropractic care and cervical artery dissection.
1. Debette, S., & Leys, D. (2009). Cervical-artery dissections: predisposing factors, diagnosis, and outcome. The Lancet Neurology, 8(7), 668-678.
2. Artenstein, A. W. (2012). The discovery of viruses: advancing science and medicine by challenging dogma. International Journal of Infectious Diseases, 16(7), e470-e473.
3. Church, E. W., Sieg, E. P., Zalatimo, O., Hussain, N. S., Glantz, M., & Harbaugh, R. E. (2016). Systematic review and meta-analysis of chiropractic care and cervical artery dissection: no evidence for causation. Cureus, 8(2).
4. Robertson J., Koyfman A., (2016). Cervical Artery Dissection: A Review, the Journal of Emergency Medicine, 51 (5, 508-515
5. Riddle, D. L., & Schappert, S. M. (2007). Volume and characteristics of inpatient and ambulatory medical care for neck pain in the United States: data from three national surveys. Spine, 32(1), 132-140.
6. Hurwitz, E. L., & Chiang, L. M. (2006). A comparative analysis of chiropractic and general practitioner patients in North America: findings from the joint Canada/United States Survey of Health, 2002–03. BMC Health Services Research, 6(1), 49.
7. Guyatt, G., Oxman, A. D., Akl, E. A., Kunz, R., Vist, G., Brozek, J., ... & Jaeschke, R. (2011). GRADE guidelines: 1. Introduction—GRADE evidence profiles and summary of findings tables. Journal of clinical epidemiology, 64(4), 383-394.
8. Cassidy, J. D., Boyle, E., Côté, P., He, Y., Hogg-Johnson, S., Silver, F. L., & Bondy, S. J. (2008). Risk of vertebrobasilar stroke and chiropractic care: Results of a population-based case-control and case-crossover study. Spine,33(45), S176-S183.