While manipulation of any kind has the potential to cause injury, stroke caused by neck manipulation is of greatest concern. Risk must always be weighed against benefit when upper neck manipulation is considered. Risk of stroke caused by neck manipulation is statistically low, but the risk is serious enough to outweigh benefit in all but a few rare, carefully selected cases.
When the RAND (Research and Development) organization published its review of the literature on cervical spine manipulation and mobilization in 1996, it concluded that only about 11.1% of reported indications for cervical spine manipulation were appropriate and that stroke and other serious complications occurred about 1.46 times per one million neck manipulations.1 In the same year, after examining 183 cases of vertebrobasilar stroke that occurred from 1934 through 1994 following neck manipulation, the National Chiropractic Mutual Insurance Company (NCMIC) concluded that “It has to be accepted that VBS [vertebrobasilar stroke] following SMT [spinal manipulative therapy] does occur.”2
Since about 90% of manipulation in the United States is done by chiropractors1 who use spinal manipulation as a primary treatment for a variety of health problems, neck manipulation is more problematic among chiropractors than among physical therapists and other practitioners who use manipulation only occasionally in the treatment of selected musculoskeletal problems.
Estimates on the incidence of stroke caused by cervical spine manipulation range from one in 400,000 to one in 5.8 million manipulations, depending upon who is doing the survey. A chiropractor-authored review of malpractice data provided by the Canadian Chiropractic Protective Association, for example, concluded that a chiropractor will be made aware of an arterial dissection only once per 5.85 million cervical manipulations.3 This stroke-manipulation ratio is widely quoted by chiropractors, despite the fact that court-litigated cases do not reflect the total number of manipulation-related strokes, most of which are unreported or undetected.
Backing away from observations that neck manipulation is a cause of stroke, a 2006 report published by NCMIC Chiropractic Solutions concluded that “The incidence of stroke in the population as a whole is no different (2 per 100,000 persons annually) than among those who received manipulation treatment of the neck,” adding that “The best scientific evidence available has shown no causative relationship between appropriately applied spinal manipulation and stroke events.”4 Many studies, however, have linked chiropractic upper neck manipulation with stroke.5,6
Recent reports produced by chiropractors argue that the incidence of stroke among persons who have had neck manipulation is “…to the same order of magnitude as that occurring in the general population,”4 and that there is “…no evidence of excess risk of VBA [vertebrobasilar artery] stroke associated with chiropractic care compared with primary care.”7 But these reports fail to distinguish strokes caused by trauma to the vertebral arteries of young healthy people from the type of strokes that occur among predisposed persons, especially the elderly. No consideration is given to the possibility that many strokes caused by neck manipulation may go unreported. When patients seek medical care for paralytic symptoms caused by release of a blood clot that was formed days or weeks earlier by neck manipulation, for example, a connection between neck manipulation and stroke may not be made. Such strokes may then be reported by primary care physicians who are unaware of preceding trauma caused by neck manipulation, thus sparing chiropractors of any blame.
The most recent chiropractor-headed study of the association between chiropractic visits and vertebrobasilar artery stroke, based on billing records, concluded that strokes associated with chiropractic neck manipulation occur because patients with headache and neck pain caused by vertebrobasilar dissection seek chiropractic care for relief of symptoms: “The increased risks of VBA stroke associated with chiropractic and PCP [primary care physician] visits is likely due to patients with headache and neck pain from VBA dissection seeking care before their stroke.”7 In other words, the report implies that a chiropractor is not to be blamed for making an incorrect diagnosis and then manipulating the neck of a patient who presents the symptoms of a stroke in progress. It goes without saying, however, that it is the responsibility of the chiropractor to recognize symptoms of stroke before manipulating the patient’s neck, especially if the chiropractor practices independently or portrays himself or herself as a primary care physician. But you cannot depend upon the diagnostic acumen of a chiropractor who believes that he or she can improve health by adjusting the spine. Physicians and therapists who refer patients to chiropractors must be cautious in selecting patients for referral, and they must take responsibility for the diagnosis when making such referrals.
Clearly, patients with acute head and neck pain that might be the result of stroke or arterial dissection should not have their necks manipulated. Elderly persons who might be susceptible to stroke because of diseased vertebral arteries should not be subjected to the risk of neck manipulation. The fact that spontaneous vertebral artery dissection can occur in susceptible persons of all ages does not excuse neck manipulation as a cause of traumatic dissection but rather underscores another reason for avoiding such treatment whenever possible.
Appropriate neck manipulation
Manipulation of the upper cervical spine should be reserved for carefully selected musculoskeletal problems that do not respond to such simple measures as time, massage, exercise, mobilization, longitudinal traction, or over-the-counter medication. Because of the tortuous route of the vertebral arteries where they thread through the transverse processes of the first cervical vertebra and then make a sharp turn to travel behind the atlas and enter the skull through the foramen magnum, head and neck rotation forced by manual manipulation should not exceed 45 or 50 degrees if kinking or traumatic dissection of these arteries is to be avoided.8,5 Rotating the head to rotate the cervical spine would force excessive rotation in the occiput-atlas-axis area where the vertebral arteries are most vulnerable and where there are no intervertebral discs and no interlocking joints to limit rotation. Rotation past 45 degrees might cause kinking of the ipsilateral vertebral artery while rotation past 50 degrees might cause kinking of the contralateral vertebral artery.8 Rapid manual rotation of the head might also cause damage by overcoming the arteries’ normal elasticity, causing tears and blood clots in the intimal lining of the vertebrobasilar arteries. The slow stretching of mobilization within a normal range of movement may be less damaging to arteries than the high-velocity low-amplitude manipulation required to rotate the cervical spine beyond its normal range of motion or to move joints into the paraphysiologic space to produce cavitation.
It seems likely that in rare cases where there is significant discomfort or loss of mobility caused by binding or fixation of a vertebral joint or by entrapment of a synovial membrane or a cartilaginous fragment, manipulation might be the treatment of choice. There is evidence to indicate that cervical spine manipulation and/or mobilization may provide short-term pain relief and range of motion enhancement for persons with subacute or chronic neck pain.1 There is no credible evidence, however, to indicate that neck manipulation is any more effective for relieving mechanical neck disorders than a number of other physical treatment modalities,9 and it is clear that adverse reactions are more likely to occur following manipulation than mobilization.10 (When manipulation is performed, a joint is moved farther than normally possible in an active movement. Passive mobilization moves a joint through its normal range of motion.) Inappropriate cervical spine manipulation may force excessive movement and worsen symptoms related to cervical disc herniation or spondylosis, producing such complications as radiculopathy or myelopathy.11 At least one study has suggested that manual therapy in the form of mobilization is more effective and less costly for treating neck pain that physiotherapy or care by a general practitioner.12 And there is reason to believe that less risk is associated with mobilization than with manipulation.10 There is no justification, however, for use of neck mobilization or manipulation as a treatment for general health problems.
All things considered, manual rotation of the cervical spine beyond its normal range of movement is rarely justified. The neck should never be manipulated to correct an asymptomatic “chiropractic subluxation” or an undetectable “vertebral subluxation complex” for the alleged purpose of restoring or maintaining health or to relieve symptoms not located or originating in the neck. There is no evidence that such subluxations exist. When a painful, actual subluxation (partial dislocation) occurs, manipulation might occasionally be helpful but is most often contraindicated.13
The bottom line is that while there might an occasional need for appropriate, properly controlled neck manipulation in the treatment of an uncomplicated musculoskeletal problem that results in loss of mobility, there is no credible support for the use of such treatment based on the chiropractic vertebral subluxation theory. Consultation with an orthopedist or a neurologist should be part of a consensus that determines the need for neck manipulation, weighing benefit against risk. Persons with certain structural or vascular abnormalities, or who might be taking blood thinners or other medications that would increase risk of bleeding, would be advised not to undergo neck manipulation for any reason.
When a sudden onset of neck pain occurs, it is absolutely essential that an attempt be made to rule out a pre-existing vertebral artery dissection before neck manipulation is done, lest manipulation releases an embolus that will travel to the brain. Sudden, severe headache might also be an indication that stroke is occurring or is about to occur. When neck pain or headache is sudden and severe, neck manipulation should not be considered until a neurologist has tested the patient for symptoms of arterial dissection or stroke. Such a careful approach would be problematic among chiropractors who base diagnosis and treatment upon detection and correction of a “vertebral subluxation complex.”14
Chiropractors vs. physical therapists
Since it may be difficult or impossible to determine beforehand who might have weak or diseased vertebral arteries or who might be vulnerable to vertebral artery dissection or stroke that could be caused or aggravated by upper neck manipulation, rotational neck manipulation should be a measure of last resort. A physical therapist trained in the use of both manipulation and mobilization for musculoskeletal problems would be less likely to use manipulation inappropriately than a chiropractor who routinely manipulates the spine for “the preservation and restoration of health.”15
According to the Association of Chiropractic Colleges (ACC), “Chiropractic is concerned with the preservation and restoration of health, and focuses particular attention on the subluxation. A subluxation is a complex of functional and/or structural and/or pathological articular changes that compromise neural integrity and may influence organ system function and general health.”15 Chiropractors who are guided by this vague paradigm (more of a belief than a theory) often manipulate the full spine of every patient for “subluxation correction.” Few chiropractors specialize in the care of back pain and other musculoskeletal problems, and only a few have renounced the chiropractic vertebral subluxation theory.
An indication that science-based chiropractic is outweighed by subluxation-based chiropractic is evident in the recent demise of the National Association for Chiropractic Medicine (NACM). (Personal correspondence with Ron Slaughter, MS, DC, August 8-09.) The NACM, founded in 1984, required its members to renounce the chiropractic vertebral subluxation theory as part of a plan to develop a science-based musculoskeletal specialty that could become a part of mainstream medicine, with emphasis on manipulation and other physical treatment methods. Only a few hundred chiropractors joined the organization. Failure of the NACM certainly does not speak well for the chiropractic profession, which continues to resist reform that would uniformly limit chiropractors in a properly defined specialty.
While physical therapists, physiatrists, osteopaths, and orthopedists sometimes manipulate the neck for a carefully selected musculoskeletal problem, chiropractors who are guided by the ACC’s subluxation paradigm may routinely manipulate the neck, thus subjecting the patient to unnecessary risk.16 Whatever the incidence of stroke per number of neck manipulations might be, this risk is greater per patient among chiropractic patients who may be manipulated many times for “health reasons” and who may be manipulated regularly for “maintenance care.” Chiropractors who renounce vertebral subluxation dogma and specialize in the care of back pain will use manipulation more appropriately. Unfortunately, there is no official or legal definition limiting chiropractors to treatment of musculoskeletal problems, making it difficult to find a properly limited chiropractor.17
There is little doubt that most chiropractors are skillful manipulators. And many chiropractors do a good job treating back pain. But until chiropractors are uniformly specialized in treatment methods and scope of practice, and chiropractic associations openly denounce the nonsense that permeates the profession, chiropractors cannot be recommended across the board. Hit-and-miss reliability among chiropractors makes it necessary for physicians and other health professionals to stay on the safe side and recommend physical therapists rather than chiropractors.
Forty-two states permit direct access to the services of physical therapists, some of whom may include use of manipulation among their treatment modalities. A physical therapist who offers neck manipulation without requiring a physician’s prescription must be prepared to take responsibility for the diagnosis and the treatment outcome. Because of the dangers associated with neck manipulation, therapists who perform such manipulation should work closely with medical specialists to determine if benefit outweighs risk.
Since physical therapists use mobilization more often than manipulation, and use much less neck manipulation than chiropractors who routinely manipulate the spine, there may be less injury and a lower incidence of stroke associated with physical therapy than with chiropractic treatment. For example, a review of 177 cases of injury caused by manipulation of the cervical spine (MCS), reported in 116 articles published between 1925 and 1997, revealed that “Physical therapists were involved in less than 2% of the cases, and no deaths have been attributed to MCS provided by physical therapists.”18
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3. Haldeman S, Carey P, Townsend M, Papadopoulos C. Arterial dissections following cervical manipulation: the chiropractic experience. Can Med Assoc J 2001;165(7):905-6.
4. Triano J, Kawchuk G. Current Concepts in Spinal Manipulation and Cervical Arterial Incidents. Clive, IA: NCMIC Chiropractic Solutions; 2006.
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8. Magee D. Orthopedic Physical Assessment. Philadelphia, PA: W.B. Saunders Company; 1987.
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13. Homola S. Chiropractic: history and overview of theories and methods. Clin Orthop Relat Res 2006; Number 444:236-42.
14. Homola S. Can chiropractors and evidence-based manual therapists work together? An opinion from a veteran chiropractor. J Man Manipulative Ther 2006;14(2):E14-E18.
15. Christensen MG, Kollasch MW, Ward R, et al. Job Analysis of Chiropractic. Greeley, CO; National Board of Chiropractic Examiners; 2005.
16. Homola S. Is the chiropractic subluxation theory a threat to public health?@ The Scientific Review of Alternative Medicine 2001;3(1):45-53.
17. Homola S. Finding a Good Chiropractor. Arch Fam Med 1998;7(Jan/Feb):20-3.
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Note: Portions of this article have been published in The Scientific Review of Alternative Medicine (Vol. 2, 2007, published in 2009) and Skeptical Inquirer (Vol. 33, No. 4, 2009).