Cassidy JD, Boyle E, Côté P, et al. Risk of Vertebrobasilar Stroke and Chiropractic Care. Spine 15 February 2008; 33(4S):S-176-S-183.
ABSTRACT: Study Design: Population-based, case-control and case-crossover study. Objective: To investigate associations between chiropractic visits and vertebrobasilar artery (VBA) stroke and to contrast this with primary care physician (PCP) visits and VBA stroke. Summary of Background Data: Chiropractic care is popular for neck pain and headache, but may increase the risk for VBA dissection and stroke. Neck pain and headache are common symptoms of VBA dissection, which commonly precedes VBA stroke. Methods: Cases included eligible incident VBA strokes admitted to Ontario hospitals from April 1, 1993 to March 31, 2002. Four controls were age and gender matched to each case. Case and control exposures to chiropractors and PCPs were determined from health billing records in the year before the stroke date. In the case-crossover analysis, cases acted as their own controls.
Results: There were 818 VBA strokes hospitalized in a population of more than 100 million person-years. In those aged <45 years, cases were about three times more likely to see a chiropractor or a PCP before their stroke than controls. Results were similar in the case control and case crossover analyses. There was no increased association between chiropractic visits and VBA stroke in those older than 45 years. Positive associations were found between PCP visits and VBA stroke in all age groups. Practitioner visits billed for headache and neck complaints were highly associated with subsequent VBA stroke.
Conclusion: VBA stroke is a very rare event in the population. The increased risks of VBA stroke associated with chiropractic and PCP visits is likely due to patients with headache and neck pain from VBA dissection seeking care before their stroke. We found no evidence of excess risk of VBA stroke associated chiropractic care to primary care.
COMMENTS: A possible association between cervical spine adjustments/manipulation and VBA strokes have been used against chiropractors for years. The studies that have been used to link the two tend to be of questionable design. One of the more recent studies in a prestigious neurology journal queried neurologists if they care who came to the ER. What kind of a retrospective study uses the memory of others rather than actual records?
Another researcher cites primarily himself.
The authors found an association between both chiropractic visits and primary care physician visits and subsequent VBA strokes. Two percent of those who had a VBA stroke had seen a chiropractor within a month of the stroke; 2.4% had seen both a chiropractor and a primary care physician; and 51% had seen only a primary care physician prior to the VBA stroke.
The conclusion is that “there is no excess risk of VBA stroke from chiropractic care.” Those that subsequently had a VBA stroke within a month of seeking either chiropractic or medical care or both had presenting symptoms – in particular, neck pain and headaches – that might be attributable to pre-existing vertebral artery dissection.
The authors also state that “there is no acceptable screening procedure to identify patients with neck pain at risk of VBA stroke.”