Critique of the Canadian Stroke Consortium's Spontaneous vs. Traumatic Arterial Dissection Study

Journal of the American Chiropractic Association, May 2004 by Haneline, Michael T, Lewkovich, Gary

Abstract

The Canadian Stroke Consortium (CSC), a nationwide network of stroke physicians in Canada, has been conducting a multi-center study concerning the relationship of trauma to cervical artery dissection (CAD) that has spanned several years. As a result of this study, Norris et al. published a non-peer-reviewed commentary in the Canadian Medical Association Journal (CMAJ) pertaining to the results of data collected during the first year. This paper, despite numerous unfavorable critiques, initiated an international media frenzy and raised unsupported public fear about the safety of cervical spinal manipulation. Since that time, the CSC has reportedly continued to gather data. An update on its latest findings is expected in the near future. Hopefully, the new research will avoid the myriad of problems that plagued the first paper. The purpose of this article is to summarize the methodological flaws, the internal biases, and the faulty conclusions of the original journal presentation by Norris et al.

Introduction

The Canadian Stroke Consortium (CSC), a group funded primarily by pharmaceutical companies, is a nationwide network of stroke physicians in Canada. The CSC has been conducting a multi-center study concerning the relationship of trauma to cervical artery dissection (CAD) that has spanned several years. As a result of this study, Morris et al. published a non-peer-reviewed commentary in the Canadian Medical Association Journal (CMAJ) pertaining to the results of data collected during the first year.1 The CSC paper indicates that stroke resulting from neck manipulation occurred in 28% (21/74) of the reported cases, which was approximately 35% of those cases that involved some degree of trauma. This percentage is significantly higher than what other authors have reported (Saeed et al. 11%,2 Mas et al. 15%,3 Biller et al. 5%/' Brandt et al. 4%,5) and data from a large case -controlled study placed it at 5% among a group of younger patients.6 Because of this statement and others, the Norn's et al. paper has been the topic of a flurry of responses from members of the chiropractic profession who were inclined to correct the apparent inconsistencies.7-12

Based on information found on the CSC Web site in Late 2003, they intend to publish updated results of the ongoing study in the near future.13 Accordingly, members of the chiropractic profession need to prepare for the near-hysterical commentary that often follows the publication of such studies. Indeed, doctors of chiropractic should be well versed on this topic and prepared to logically defend the relative safety of cervical manipulation when the occasion arises. This paper will attempt to offer a comprehensive critique of the Norn's et al. paper and the study that it was based on.

Discussion

The CSC study is laden with methodological flaws, questionable findings, shoddy research, and unsupported conclusions. One of the most serious problems with this study is poor construction of the survey instrument used to gather data for reporting CADs to the CSC. In the first part of the questionnaire, there was a leading question that could potentially have caused the physician respondents to provide biased answers. The question dealt with whether or not trauma was related to the CAD under consideration and reads: "Cervical trauma/manipulation." This was followed by a second part of the question asking for a description of the trauma that was involved.14 Leading questions, those that suggest or hint at a particular answer, should be avoided in questionnaire composition.15 If the researchers were truly interested in gathering accurate information, they would not "plant seeds" in the minds of the physicians participating in the study by mentioning manipulation as a trauma possibility. After all, there were many other potential sources of trauma that could have been submitted and, based on the patient's history, the respondents should have been fully capable of establishing the correct answer without prompting.

As a corollary to the above, the role of spinal manipulation and CAD has already been the topic of considerable controversy in the Canadian press.16 Given this climate, the phrasing of any research instrument becomes even more critical to minimize the perpetuation of the latest media frenzy. Canadian physicians and patients are certainly not immune to the biases of the world around them, and it is difficult under even ideal circumstances for researchers to obtain useful data without compounding the problem by using socially charged topic selection and question phrasing.

Non-response bias may also have been present in this study, as busy neurologists treating the study's CAD patients were asked to complete yet another form. Some of these doctors may not have completed the questionnaire merely because they were occupied with patient care issues and didn't want to take the extra time to fill out the questionnaire. On the other hand, some of them may have been more inclined to complete the form when chiropractic manipulation or some unusual form of trauma was involved, resulting in selection bias. These biases may also have contributed to the authors' findings that most of the dissections were associated with sudden neck movement (81%).