Stroke Risk from CMT

Stroke Risk from CMT? Is the Pressure Finally Off? Arthur C. Croft, D.C., M.P.H., F.A.C.O.

The controversy concerning the risk for vertebrobasilar (VB) stroke from chiropractic manipulative therapy (CMT) has droned on year after year, initially fueled by a small number of both real and questionable cases, and followed by a flawed survey, a couple of more recent retrospective studies, and a couple of recent cases that have been driven to virtual celebrity status. We and others have addressed the limitations of some of the earlier literature (1).

In the more recent literature we find two papers that reflect the gradual shift towards an increasingly misinformed orthodoxy in thinking among the medical profession. One, published in the Southern Medical Journal, exhorts medical practitioners to be cautious of CMT (2). The authors note that the most common risk factors are migraine, hypertension, oral contraceptive use and smoking, and that stroke following cervical spine manipulation is more common than the literature reports. This latter opinion springs from a highly-questionable survey of California neurologists who were not required to verify their memory (3). According to the Southern Medical Journal authors, cervical CMT is very risky and they urge "extreme caution" in recommending it. I note that the authors did not happen to find a number of more grounded and balanced studies on this subject, such as ours (1) or the larger RAND study I worked on earlier (4). In the RAND study, a multidisciplinary panel (including myself) concluded that cervical CMT was generally safe and indicated for a number of clinical conditions.

The Southern Medical Journal authors are guilty of literature dredging, basing their opinions on, for example, the first two cited papers, each reporting a single case, and both dating back to the 1950s. The early literature is problematic because it consists of case reports, some of which are quite dubious. For example, we found one such case where a woman was seen by a chiropractor for neck pain, received therapy (CMT), and later reported relief of her symptoms. Four days later, she began to complain of symptoms of vertebral artery dissection (VAD). This was attributed to the CMT. In this case, the likelihood that CMT caused the VAD is improbable given the chronology. VAD, it should be noted, is most often spontaneous or follow everyday minor insults.

One would think that if this were truly the public health epidemic some believe it to be, opponents of CMT might be able to harness more than single cases from a half a century past. Instead, for the most part, this controversy is fueled by a smattering of very publicized cause celebres. In the RAND study we found that the risk for severe complication, which would include VAD and/or stroke, some of which are self-limiting and some of which are not, or are fatal, is about one in 400,000 to one in a million.

By my calculations, if our RAND statistics are correct, we would expect about 83-250 serious complications from cervical CMT in the U.S. each year. Placing public health issues in contrast, one of the most common treatments medical providers use to treat neck pain is NSAIDS. According to government statistics, 33,000 people die each year of complications from taking NSAIDS 5. A JAMA study reported that about 106,000 died in the year 1994 from adverse drug reactions (ADR) (6), while 2.5 million suffered from drug-induced diseases. Some 32,000 die from complications from hip fractures induced by falls due to medication side effects. These occur in a very wide range of commonly prescribed drugs. Some 163,000 suffer from drug- induced or worsened memory loss, and the list goes on and on.

More recent data indicate that since 1998 the problem with ADR has more than doubled (7). And, like all government statistics, this is probably only scratching the surface of the problem. There are reports that only 0.3% to perhaps 33% of ADR are actually reported. In many cases, doctors end up treating the side effects of one drug with another drug, so they too are often in the dark as to the real size of the problem. And what is the incentive for physicians reporting an ADR? After drug-induced disease or death, we should also probably look at the complications of surgery and other invasive medical procedures and their overall efficacy and risk. The chilling and unexpected fatal risks of epidural steroid injections has prompted some to suggest a moratorium on this procedure (8).

Meanwhile, another warning against CMT comes recently from Portugal from Gouveia, et al. (9). We wrote to the journal, voicing concern over many of their assumptions and conclusions. That letter was recently published and I would be happy to provide a copy to interested readers (10). But the best work was yet to come.

David Cassidy and colleagues have most recently brought some science and sanity to what can only charitably be described as a professional witch hunt. This comes at a time when some medical groups are now calling for a ban on cervical spinal manipulation by chiropractors, and at a time when chiropractors were still reeling under the misguided onslaught of the somewhat murky Chiropractic Stroke Awareness Group, which has posted billboard advertisements, and now television advertisements, warning the public that chiropractic spinal manipulation causes stokes and serious disability (11). This new study by Cassidy, et al., which was part of the Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders project, is now the definitive study on the subject.

The CMT-induced stroke controversy saw a resurgence after two highly-publicized stroke cases in Canada were attributed to CMT in the 1990s. Two case control studies subsequently pointed an ominous finger at CMT. In one, the authors looked at Ontario health data with 582 cases of vertebrobasilar artery (VBA) stroke. They showed that persons aged under 45 years, who had had a VBA stroke, were five times more likely to have seen a chiropractor within one week prior to the stroke. Not a cause and effect certainty, but a smoking gun (12). In the other smaller study (n=51), in a subgroup analysis, they showed that the cases with vertebral artery dissections were six times more likely to have consulted with a chiropractor in the 30 days prior to the vascular event (13).

The most recent study by Cassidy, et al. looked at all residents of Ontario, Canada over a nine year period (1993-2002). This represents the equivalent of 109 million person-years of observation. Their design looked at not only visitations to chiropractors in the period preceding the stroke, but also visits to their primary care physician (PCP). The idea in this design is that a PCP, in their work-up of patients, is unlikely to subject them to any maneuver that might produce a stroke. So the proportion of people who did have a stroke and who had recently seen their PCP should represent the background rate of VBA stroke in the population.

In total they found 818 VBA strokes that met criteria. And the results were interesting. There was an increased odds ratio (OR) for the stroke patients in terms of having seen a chiropractor in the period prior to the stroke (OR=1.37; 95% CI 1.04-1.91). But the OR for seeing the PCP was about the same. In fact, there was a slightly stronger association. They theorized that patients with VBA strokes are likely to consult with PCP or their chiropractors because of the symptoms. Thus, the confounder was identified and, although this study does not absolve CMT of all culpability in all cases of stroke, in the words of the authors, ". . . [CMT] is unlikely to be a major cause of these rare events." Note the comment about rare event. This fact underscores the insanity of chasing after the specter of stroke by a profession whose ADRs in 1994 added up to the fourth to the sixth leading cause of death in the U.S. (6).

This Cassidy, et al. study can be considered the final word on the subject and clearly is going to be welcome news to DCs everywhere. It may be a bit late, since much indelible damage has been done already. Many DCs have heard from patients, for example, that their medical doctor does not want their neck adjusted. But this is a paper that should be available to give out to patients, medical doctors, claims adjustors, legislators, and anyone else who is concerned.

Meanwhile, practitioners of CMT should remain highly vigilant concerning the possibility of VAD. These patients may present with neck pain and/or headaches, usually unilateral and described as a quality and severity of pain the patient has never experienced in the past. Manipulation of these patients could precipitate a stroke.

The chiropractic profession should continue to investigate this area of stroke in an effort to understand how these injuries occur and to develop strategies to minimize the risk. Meanwhile, our medical detractors would be performing a much more rational and important public health service by monitoring their own performance and looking at ways to better understand how to more safely use the drugs they currently use as their alternative to infinitely safer treatments like CMT. Ironically, recent research has identified CMT as being significantly more clinically effective than medical care (14,15). In fact, in a recent Cochrane review for mechanical neck disorders, manipulation made it into the highest level of evidence (16). No medical interventions achieved this level of evidence. CMT: safe and effective. Use of prescription drugs: much less safe and proven to be ineffective for managing spinal pain.

References 1. Haneline M, T. , Croft AC, Frishberg BM. The association of internal carotid artery dissection and chiropractic manipulation. Neurologist 2003;9(1):35-44. 2. Leon-Sanchez A, Cuetter A, Ferrer G. Cervical spine manipulation: an alternative medical procedure with potentially fatal complications. South Med J. 2007;100(2):201-3. 3. Lee KP, Carlini WG, McCormick GF, Albers GW. Neurologic complications following chiropractic manipulation: a survey of California neurologists. Neurology. 1995;45(6):1213-5. 4. Coulter ID, Hurwitz EL, Adams AH, Meeker WC, Hansen DT, Mootz RD, Aker PD, Genovese BJ, Shelkelle PG. The appropriateness of manipulation and mobilization of the cervical spine. 1 ed. Santa Monica: The RAND Corporation; 1996. 5. Wolfe SMea. Worst Pills, Best Pills. A Consumer's Guide to Avoiding Drug-Induced Death and Illness. New York: Simon & Schuster, Inc.; 2005. 6. Lazarou J, Pomeranz BH, Corey PN. Incidence of adverse drug reactions in hospitalized patients: a meta- analysis of prospective studies. JAMA. 1998;279(15):1200-5. 7. Moore TJ, Cohen MR, Furberg CD. Serious adverse drug events reported to the Food and Drug Administration, 1998-2005. Arch Int Med. 2007;167(16):1752-9. 8. Scanlon GC, Moeller-Bertram T, Romanowsky SM, Wallace MS. Cervical transforaminal epidural steroid injections: more dangerous than we think? Spine. 2007;32(11):1249-36. 9. Gouveia LO, Castanho P, Ferreira JJ, Guedes MM, Falcão F, Melo TP. Chiropractic manipulation: Reasons for concern? Clin Neurol Neurosurg. 2007;109:922-5. 10. Croft AC, D'Antoni AV. Chiropractic manipulation: Reasons for concern? Clin Neurol Neurosurg. 2008;110(4):422-3. 11. Cassidy JD, Boyle E, Cote P, He Y, Hogg-Johnson S, Silver F, Bondy S. Risk of vertebrobasilar stroke and chiropractic care: results of a population-based case-control and case-crossover study. Spine. 2008;33(45):S176-S83. 12. Rothwell DM, Bondy SJ, Williams JI. Chiropractic manipulation and stroke: a population-based case-control study. Stroke. 2001;32(5):1054-60. 13. Smith WS, Johnston SC, Skalabrin EJ, Weaver M, Azari P, Albers GW, Gress DR. Spinal manipulative therapy is an independent risk factor for vertebral artery dissection. Neurology. 2003;60(9):1424-8. 14. Giles LGF, Muller R. Chronic spine pain: a randomized clinical trial comparing medication, acupuncture, and spinal manipulation. Spine 2003;28(14):1490-502. 15. Muller R, Giles LG. Long-term follow-up of a randomized clinical trial assessing the efficacy of medication, acupuncture, and spinal manipulation for chronic mechanical spinal pain syndromes. J Manipulative Physiol Ther. 2005;28(1):3-11. 16. Gross AR, Goldsmith C, Hoving JL, Haines T, Peloso P, Aker P, Santaguida P, Myers C. Cervical Overview Group. Conservative management of mechanical neck disorders: a systematic review. J Rheumatol. 2007;34(3):1083-102.

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