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Anthony L. Rosner, Ph.D.
April 10, 2001

Publisher's Note

References

The recent publication by Norris and his colleagues¹ appears as yet another example from a string of recent publications which unsuccessfully attempt to single out chiropractic as a significant causative factor of cervical artery dissection and strokes.^2-5 Although it claims superiority over previous studies due to its prospective design, it is as arrogant as it is mind-numbing in its unwillingness to disclose the essential details of its methodology which validate any scientific study.

What was the instrument used to capture the incidence of arterial dissections? Within what time period following the precipitating factor [spinal manipulation or other] were vertebral artery dissections noted? How many of these were transient? In order to derive a true denominator for the fraction of manipulative procedures resulting in arterial dissections, what was the total number of manipulations performed? What was the technique employed? Given the fact that vertebrobasilar artery accidents are often attributed to manipulators falsely represented as fully licensed and trained chiropractors,⁶ who were in fact the individuals performing the manipulations boldly stated to result in strokes in 21 of the 74 patients tested? These are but a few of the most elementary types of questions that would be asked for even a science fair project, yet they remain unanswered in Norris' study.

To its credit, this manuscript correctly suggests that a variety of neck movements could precipitate vertebrobasilar artery events, in keeping with a large and compelling body of literature.^7-12 Spinal manipulation represents but a tiny fraction of these precipitating movements and is almost impossible to identify with any regularity as the predominating cause of an arterial dissection.

The author's categorical statement in the paper that "there is no doubt that chiropractic neck manipulation can result in the dissection of the carotid or vertebral arteries leading to stroke" represents a blatant contradiction of all these arguments and is completely without support from either the data within the paper itself or the literature which it cites. Rather, it reveals a deep-seated prejudice of Norris which is only reinforced by his letter of response which continues to refuse to disclose any details supporting his contention that manipulation of the cervical spine is associated with 27% of the strokes observed in 50 cases per year. Worse, Norris flaunts his prejudice by stating that "the research question is not whether neck manipulation can result in dissection of a cervical artery, for it surely can [italics mine]..."¹³ The point here is: so can star gazing, yoga, hair washing, driving a vehicle, archery, wrestling, emergency resuscitation, rap dancing, sleeping, swimming, and Tai Chi—at frequencies at or above those which can be attributed to spinal manipulation.^7,14,15

Not only are causative events and caregivers not clearly identified by Norris' or other studies, but so is the temporal sequence. Many of the reported instances of cerebrovascular accidents attributed to chiropractic occurred more than 1 hour after manipulative therapy, measured in days¹⁶ or weeks.⁵ Because of these three major ambiguities [caregiver, precipitating event, time to event], the most plausible model of strokes brought on by arterial dissection which needs to be heeded by Dr. Norris and his colleagues is that such events are cumulative rather than traumatic, culminating years of turning the head and possibly extending the spine as well. Most if not all of the chiropractic incidents described probably represent movements of the artery in a select and high-risk group of patients which most likely would have occurred [or possibly did occur] during some everyday activity. The challenge for chiropractors and medical practitioners alike is to be able to identify such high-risk patients in advance of their experiencing any number of lifestyle activities, in which spinal manipulation plays only an extremely limited role.

PUBLISHER'S NOTE:

The article referenced herein was published in a recent issue of the Canadian Medical Association Journal.¹ It was written by John W. Norris, Vadim Beletsky, and Zurab G. Nadareishvilli, on behalf of the Canadian Stroke Consortium. The article is entitled, "Sudden neck movement and cervical artery dissection."

REFERENCES:

¹Norris JW, Beletsky V, Nadareishvilli ZG, Canadian Stroke Consortium. Canadian Medical Association Journal 2000; 163(1): 38-40.