Chiropractic and Cervical Arterial Dissection:
Causal Relationship or Medical Dogma?
By Mark Studin
William J. Owens
A report on the scientific literature and commentary
There has been much controversy over the last 2 decades about the perceived causal relationship between a chiropractic cervical adjustment and dissecting arterial aneurysm on the internet, in the literature and in the beliefs of some in the medical community. Prior to examining the published facts, lets first clarify what an arterial dissection is.
According to Haneline and Rosner (2007)
Arterial dissection is an uncommon vascular wall condition that typically involves a tear at some point in the artery's lining and the formation of an intimal flap, which allows blood to penetrate into the muscular portion of the vessel wall. Blood flowing between the layers of the torn blood vessel may cause the layers to separate from each other, resulting in arterial narrowing or even complete obstruction of the lumen (Fig 1). Moreover, pulsatile pressure damages the muscular layer, resulting in a splitting or dissection of the intimal and medial layers that may extend along the artery variable distances, usually in the direction of blood flow.Another way for dissection to occur involves a primary intramural hemorrhage of the vasa vasorum, which builds pressure between the intimal and medial layers and may eventually rupture into the vessel's true lumen. Occasionally, a double lumen (also known as false lumen) is formed when the subintimal hemorrhage ruptures back into the arterial lumen distally. (pgs. 113-114)
In addition, Haneline and Rosner (2007) wrote a decade ago:
Of special interest to chiropractors is the role cervical spine manipulation [CSM] plays, if any, in the pathogenesis of CAD [Cervical Artery Dissection]. Indeed, patients do experience CAD on rare occasions after CSM, making knowledge about the cervical arteries, the predisposing factors, and the pathogenesis of the condition important for chiropractors. (pg. 110)
This comment, early in the potential relationship between cervical adjusting and cervical arterial dissection [CAD] warranted a warning to healthcare provider about CAD and cervical adjusting making it important to understand the cervical arteries. This is underscored by the authors themselves being chiropractors and memorizing this “caveat” to the profession.
In a September 2017 presentation by Candice Perkins MD, Neurology, Vascular Neurology (an attending stroke neurologist and both an Associate and Assistant Professor of Clinical Neurology at the State University of New York at Stony Brook Hospital and Medical Center from 2001 - 2016) in New York, she stated that there is zero evidence for direct causal relationship between stroke and a chiropractic cervical adjustment performed by a licensed chiropractor in the appropriate clinical presentation. Dr. Perkins went on to explain that there are numerators and denominators. The denominator are strokes and the presence of a patient with a stroke. The numerator is the associated incidence. In her vast experience with stroke, there are an unlimited number of numerators with chiropractic being one, however if one uses that same equation, there are hundreds of other equally potential factors with primary care medical visits being of equal incidence. In addition, with her understanding chiropractic as a patient and from the literature, there is scant evidence that a chiropractic adjustment can be the causative factor of cervical dissecting aneurysm.
Researchers from the University of Pennsylvania Department of Neurosurgery came to the same conclusions. In a systematic and meta-analysis of chiropractic care and cervical arterial dissection, they concluded:
There is no convincing evidence to support a causal link between chiropractic manipulation and CAD. (pg. 1)
Church et. Al reviewed 253 published articles and scored them on a GRADE system with 4 variables, high, moderate, low and very low in reliability of the research available on CAD and chiropractic adjustments. They concluded:
Scrutiny of the quality of the body of data using the GRADE criteria revealed that it fell within the “very low” category. We found no evidence for a causal link between chiropractic care and CAD. This is a significant finding because belief in a causal link is not uncommon, and such a belief may have significant adverse effects such as numerous episodes of litigation. (pg. 6)
Perhaps the greatest threat to the reliability of any conclusions drawn from these data is that together they describe a correlation but not a causal relationship, and any unmeasured variable is a potential confounder. The most likely potential confounder in this case is neck pain. Patients with neck pain are more likely to have CAD (80% of patients with CAD report neck pain or headache), and they are more likely to visit a chiropractor than patients without neck pain. (pg. 7)
This is the same opinion of Dr. Perkins as reported above, where the presence of CAD does not have a causal relationship simply because the neck pain brought them to a chiropractor. The CAD would have happened with or without the chiropractic adjustment as is concluded by medical experts and the literature.
To further the argument, Cassidy, Boyle, Cote`, He, Hogg-Johnson, Silver and Bondy (2008) reported:
There were 818 VBA [Vertebral Basilar Artery] 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. (pg. S176)
Murphy (2010) reported,
Therefore, based upon the best current evidence, it appears that there is no strong foundation for a causal relationship between CMT [Chiropractic Manipulative Therapy] and VADs [Vertebral Artery Dissection]. The most plausible explanation for the association between CMT and VADs is that individuals who are experiencing a vertebral artery dissection seek care from a chiropractic physician or other manual practitioner for relief of the neck pain and headache that results from the dissection. Sometime after the visit the dissection proceeds along its natural course to produce arterial blockage, leading to stroke. This natural progression from dissection to stroke appears to occur independent of the application of CMT. (pg. 4)
Church, Sieg, Hussain, Glantz and Harbaugh (2016) concluded, and an opinion that appears to reflect the facts of the issue and in accordance with those in chiropractic and medical academia based upon the author’s strong agreement:
Our systematic review revealed that the quality of the published literature on the relationship between chiropractic manipulation and CAD is very low. A meta-analysis of available data shows a small association between chiropractic neck manipulation and CAD. We uncovered evidence for considerable risk of bias and confounding in the available studies. In particular, the known association of neck pain both with cervical artery dissection and with chiropractic manipulation may explain the relationship between manipulation and CAD. There is no convincing evidence to support a causal link, and unfounded belief in causation may have dire consequences. (pg. 10)
In spite of the very weak data supporting an association between chiropractic neck manipulation and CAD, and even more modest data supporting a causal association, such a relationship is assumed by many clinicians. In fact, this idea seems to enjoy the status of medical dogma. (pg. 9)
That is the final definitive opinion of the Neurosurgery Department at the University of Pennsylvania.
Stroke Rehabilitation and The Positive Effects of Chiropractic on the Response to the Central Nervous System and Motor Training Tasks
A report on the scientific literature
Mark Studin DC, FASBE (C), DAAPM, DAAMLP
Whithall, McCombe Waller, Silver, and Macko (2000) reported, "Stroke is the third leading cause of death in the United States and the leading cause of adult disability. Annually, approximately 750,000 Americans suffer a stroke. Although incidence rates have remained constant over the last 3 decades, mortality has declined, leaving an increasing number of patients requiring rehabilitation. Approximately two thirds of stroke survivors have residual neurological deficits that persistently impair function. Specifically, dysfunction from upper extremity (UE) hemiparesis [weakness on one side of the body] impairs performance of many daily activities such as dressing, bathing, self-care, and writing, thus reducing functional independence. In fact, only 5% of adults regain full arm function after stroke, and 20% regain no functional use. Hence, alternative strategies are needed to reduce the long-term disability and functional impairment from UE hemiparesis [weakness on one side of the body]" (p. 2390).
According to Kleim and Jones (2008), neuroscientists (specialists who study how the brain and nervous systems work) are often asked about specific therapies that should be included in clinical treatment programs. They go on to report that the data points to brain cells possessing the ability to alter their structure and function in response to a variety of internal and external pressures and is called "neural plasticity." They go on to say that, "Neural plasticity is believed to be the basis for both learning in the intact brain and relearning in the damaged brain that occurs through physical rehabilitation. Neuroscience research has made significant advances in understanding experience-dependent neural plasticity, and these findings are beginning to be integrated with research on the degenerative and regenerative effects of brain damage" (Kleim & Jones, 2008, p. S225). When you any type of brain damage, the goal is to limit additional damage and help restore as much function as possible.
Whithall et al. (2000) reported that, " Traditionally, methods of stroke rehabilitation have been focused on the first 3 months after stroke and consist largely of passive (nonspecific) movement approaches or compensatory training of the nonparetic [non affected] arm.
This time window is consistent with natural history studies of stroke recovery that show a plateau after 3 months. Recently, both the paradigms for rehabilitation interventions and the time frame for possible UE motor recovery have been challenged. Experiments demonstrate that functional gains and possible neural plasticity can occur, via active practice, long after spontaneous recovery would be expected to end. For example, monkey models of chronic stroke demonstrate functional recovery as well as cortical reorganization after being forced to use their paretic limb. On the basis of this 'forced-use' paradigm, Taub, Wolf, and colleagues constrained the nonparetic [non affected] arm of patients with chronic stroke and forced the use of the paretic arm in task-specific activities in an intensive 2-week protocol" (p. 2390).
The goal of rehabilitation is to create new pathways for the brain to express itself in the form of movement and function to enable the stroke victim to regain as much function as possible. This allows the individual to live as normal a life as he/she can without care and support from aides, devices and specialists, rendering a level of physical and resultant emotional independence.
Taylor and Murphy reported in 2010 that when motor activity is followed by a chiropractic spinal manipulation/adjustment, it altered the way in which the central nervous system responded to motor training tasks. In both the patient with and without recurring neck pain, it positively affected the process of use-dependant neural plastic changes. The research went on to report that spinal manipulation/adjusting alone leads to improved function. However, spinal manipulation/adjusting in combination with motor training tasks "...not only results in altered sensorimotor integration but also alters the way the CNS responds to a functional task..." (Taylor & Murphy, 2010, p. 268). Taylor goes on to report, "The results of this study suggests that this is possible, as an improved ability to filter somatosensory information in sensorimotor integration circuits was observed after the same 20-minute motor training task, when this was preceded with spinal manipulation of the subjects' dysfunctional cervical joints. This finding was similar to what has been previously observed after spinal manipulation alone and indicates that spinal manipulation improves gating or filtering of sensory information, an ability the CNS retains even after the motor training intervention" (Taylor & Murphy, 2010, p. 269). While no one suggests that manipulation/adjusting should replace motor training or skill acquisition, the results indicate that manipulation should significantly improve the outcomes of rehabilitation with stroke victims.
1. Whithall, J., McCombe Waller, S., Silver, K. H. C., & Macko, R. F. (2000). Repetitive bilateral arm training with rhythmic auditory cueing improves motor function in chronic hemiparetic stroke. Stroke, 31 (10), 2390-2395.
2. Kleim, J. A., & Jones, T. A. (2008) Principles of experience-dependant neural plasticity: Implications for rehabilitation after brain damage, Journal of Speech, Language, and Hearing Research, 51(Suppl. Neuroplasticity),S225-S239.
3. Haavik Taylor, H., & Murphy, B. (2010). The effects of spinal manipulation on central integration of dual somatosensory input observed after motor training: A crossover study. Journal of Manipulative and Physiological Therapeutics, 33(4), 261-272.
Stroke Risks While Under Chiropractic Care
Debunking the Myth that Chiropractic Causes Stroke
A report on the scientific literature
Gerard Clum DC, Past President, Life Chiropractic College West
Mark Studin DC, FASBE (C), DAAPM, DAAMLP
According to the American Heart Association (2010), a stroke "...is a disease that affects the arteries leading to and within the brain. It is the No. 3 cause of death in the United States, behind diseases of the heart and cancer. A stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or bursts. When that happens, part of the brain cannot get the blood (and oxygen) it needs, so it starts to die...Stroke can be caused either by a clot obstructing the flow of blood to the brain (called an ischemic stroke) or by a blood vessel rupturing and preventing blood flow to the brain (called a hemorrhagic stroke)...The brain is an extremely complex organ that controls various body functions. If a stroke occurs and blood flow can't reach the region that controls a particular body function, a stroke will ensue, then that part of the body won't work as it should" (http://www.strokeassociation.org/STROKEORG/AboutStroke/About-stroke_UCM_308529_SubHomePage.jsp).
The AHA (2010) also posts signs and symptoms of an impending stroke. These include numbness or weakness of one side of the face, sudden confusion, difficulty speaking or understanding, problems seeing out of one or both eyes, sudden trouble walking, dizziness, loss of balance or coordination, and severe and sudden headaches with no known cause.
The blood supply to the brain is provided through the vertebral arteries and the carotid arteries. Problems in any of these arteries can result in the development of a thrombus (clot) or an embolism. If the thrombus is large enough it can occlude the normal blood flow. If an embolism occurs, it can move through the circulation into the brain and occlude blood flow. Either way, a stroke can be the result of these situations. One of the unique characteristics of strokes of this nature is that they can involve neck pain and headache.
Many patients will seek chiropractor care for neck pain and headaches. In the great majority of cases, the pain involved is not related to a stroke. However, on occasion, it may be. When the pain is related to a stroke, some of these patients developed a full range of stroke symptoms. Over the years, reports in the popular press and the scientific literature have suggested or stated outright that in patients who experience a stroke following chiropractic care, the stroke was caused by the chiropractor! We now know that this is very unlikely to be the case. What is far more likely is that the patient developed a thrombus or embolism in their vertebral arteries, producing neck pain and headache. This person sought health care for the pain. Whether they saw a chiropractor or their medical provider, they would progress on to a stroke at virtually the same rate. While the argument that the chiropractor caused the problem is convenient, the science indicates that it is in all likelihood a mistake to draw such a conclusion.
In 2008, Cassidy, Boyle, Côté, He, Hogg-Johnson, Silver, and Bondy studied the occurrence of this problem in the province of Ontario over a nine year period with a database representing almost 110 million person-years (12.2 million people, studied over 9 years equals 110 million person-years). The purpose of this study was to investigate if an association between chiropractic care and vertebral basilar artery stroke exceeded the association between medical primary care providers and vertebral basilar artery stroke. The premise was that if there was a greater association between chiropractic care and this stroke then one could logically say there was a cause and effect relationship between chiropractic care and this problem. There was no greater likelihood of a patient experiencing a stroke following a visit to his/her chiropractor than there was after a visit to his/her primary care physician. The results were conclusive; there was no greater association between manipulation (chiropractic adjustments) and ischemic stroke or TIA's (transient ischemic attacks).
The research did conclude that overall, 4% of stroke victims had visited a chiropractor within 30 days of their strokes, while 53% of the stroke cases had visited their medical primary care providers within the same time frame. The authors offer the perspective that because neck pain is associated with some stroke, patients visit their doctors prior to the development of a full-blown stroke scenario. Cassidy et al. (2008) noted, "Because the association between chiropractic visits and [vertebral basilar artery] stroke is not greater than the association between PCP [medical primary care providers] visits and [vertebral basilar] stroke, there is no excess risk of [vertebral basilar] stroke from chiropractic care" (p. S180). In fact, the incident of chiropractic vs. medical care was substantially lower in certain situations based upon the data.
In 2010, Murphy considered the argument that a chiropractic manipulation could cause stroke and concluded, "...if this is a possibility, it would have to be considered so rare that a case-control and case crossover study covering over 109,000,000 person-years failed to detect it" (http://www.chiroandosteo.com/content/18/1/22). He also reports that "... in 20% of cases of [vertebral artery dissection and stroke] the individual does not have neck pain or headache and in a very small percentage of vertebral artery dissections can occur in a person who has no symptoms of any kind. Thus, in cases in which an asymptomatic individual experiences [vertebral artery dissection and stroke] after [chiropractic manipulation] it is not clear whether manipulation was a cause or contributing factor to the dissection or whether the patient had an asymptomatic arterial dissection prior to the chiropractic visit" (Murphy, 2010, http://www.chiroandosteo.com/content/18/1/22). He concluded his report with the following, "...current evidence indicates that [vertebral artery dissection and stroke] is not a 'complication to [chiropractic manipulation]' per se. That is, the weight of the evidence suggests that [chiropractic manipulation] is not a cause of [vertebral artery dissection and stroke]..." (Murphy, 2010, http://www.chiroandosteo.com/content/18/1/22).
The real issue is not whether chiropractic or medical primary care causes stroke, as the research conclusively refutes this, but rather it is an issue of public awareness and perception. The argument must shift to the real issue of protecting the public and making people aware of the importance of recognizing risk factors and of gettiing immediate care to avoid long term disability or death.
Murphy (2010) offers the following advice, "...engage in a public health campaign to educate the public about the warning signs and symptoms of this uncommon but potentially devastating disorder...public education materials regarding stroke in general are available from organizations such as the American Stroke Association (http://www.strokeassociation.org/presenter.jhtml?identifier=3030387 accessed 1 April 2010) the National Stroke Association (http://www.stroke.org/site/PageServer?pagename=HOME accessed 1 April 2010) the British Stroke Association (http://www.stroke.org.uk/information/index.html accessed 22 May 2010), the Heart and Stroke Association of Canada (http:/ / www.heartandstroke.com/ site/ c.ikIQLcMWJtE/ b.2796497/ k.BF8B/ Home.htm?src=home accessed 22 May 2010) and the National Stroke Foundation - Australia (http://www.strokefoundation.com.au/ accessed 22 May 2010)..." (http://www.chiroandosteo.com/content/18/1/22).
1. American Heart Association, Inc. (2010). About stroke. Retrieved from http://www.strokeassociation.org/STROKEORG/AboutStroke/About-stroke_UCM_308529_SubHomePage.jsp
2. American Heart Association, Inc. (2010). Warning signs. Retrieved from http://www.strokeassociation.org/STROKEORG/WarningSigns/Warning-Signs_UCM_308528_SubHomePage.jsp
3. American Heart Association, Inc. (2010). Ischemic (clots). Retrieved fromhttp://www.strokeassociation.org/STROKEORG/AboutStroke/TypesofStroke/IschemicClots/Ischemic-Clots_UCM_310939_Article.jsp
4. Cassidy, J. D., Boyle, E., Côté, P., He, Y., Hogg-Johnson, S., Silver, F. L., & Bondy, S. J. (2008). Risk of vertebrobasilar stroke and chiropractic care: Results of a population-based case-control and case-crossover study. Spine, 33(45), S176-S183.
5. Murphy, D. R. (2010). Current understanding of the relationship between cervical manipulation and stroke: What does it mean for the chiropractic profession? Chiorpractic & Osteopathy, 18(22), http://www.chiroandosteo.com/content/18/1/22