I once had a patient in my practice, who regularly visited my office wearing a large anti-chiropractic button prominently displayed on her blouse: You know, one of those things with the word “chiropractic” circled in red, with a seemingly redder line struck through it. When I first saw this unusual display of health care opinion, I asked her what was up with the “no chiropractic” campaign, and she responded that she had had a friend who suffered a stroke as a result—she said—of chiropractic manipulation.

This display of medical activism piqued my medical curiosity, particularly as a number of my chronic pain patients did routinely visit chiropractors, and I recall reading up on the subject: I did discover that serious complications following spinal manipulative therapy (SMT), including stroke, were quite rare, with estimates for events associated with cervical spine manipulations varying between 1 in 400,000 to 1 in 5.6 million. However, these estimates were provided with the caveat that it is far from certain that there is a causal relationship between SMT and stroke.

A recent article in the “International Journal of Clinical Practice” attempts to tackle this SMT and stroke connection mystery.

It is important to keep in mind that stroke is a significant cause of morbidity and death, even in individuals under age 45, with the most frequent risk factors being high cholesterol, smoking, and high blood pressure; but up to a third of stroke cases have an undetermined etiology—other risk factors implicated include obesity, migraine, birth control pill use, illicit drug use, etc.. Stroke can be the result of vertebral artery dissection (VAD), which has been reported to occur after hyperextension movements of the cervical spine (such as might occur in archery, ceiling painting, or modern dance), minor traumas, falls, or spontaneously.

The vertebral artery becomes the basilar artery as it enters the base of the skull, and bends sharply from a vertical to a horizontal path; and thus, common sense would have it that this should be the site where VAD as a result of SMT should occur. However, the authors of the article point out that many cases of VAD after SMT have occurred at most sites along the length of the vertebral artery, including the intracranial aspects of that artery. It would appear that the vertebral artery has been weakened by some other factor which precedes the SMT. And in fact, vascular accidents have been reported after many types of neck movement, including movements associated with the playing of golf, soccer, baseball, and running.

A survey of neurologists, fraught with recall bias, concluded that the number of cases of VAD after chiropractic was grossly underestimated. However, it could be that VAD was commencing as a result of minor trauma, sports, sustained neck positions, etc. A patient would thus complain of neck pain and possibly headache pain, leading him or her to seek relief from a visit to a chiropractor. A rushed chiropractor may not take a thorough clinical history, overlooking the symptoms of a possible evolving VAD, and perform SMT when it may have been contraindicated—this in turn exacerbating the progress of the VAD, leading to stroke.

The article concludes that compelling evidence just does not exist that allows one to conclude that SMT is a cause of stroke. Of course, any physical insult, including SMT, could serve as the final coup de grace where there is pre-existing vertebral artery pathology. All this only reinforces the importance of talking to a patient: Take those few moments to ask about any recent, however minor, neck trauma; ask about any change in chronic neck pain or headache; ask about any recent infection; ask about predisposing lifestyle factors.

That being said, the health care profession still needs the long-term prospective studies in order to assess the safety of cervical spine SMT as it relates to stroke. At this time, there are just too many confounding factors to make any conclusions.

You don’t have to discard that “no chiropractic” button; but you might want to put it away for now.

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