Spinal manipulation and stroke

By Dr. Vic Weatherall

Spinal joint "thrust manipulation" has been practiced by manual therapists for centuries. It's a regulated act in Ontario, practiced primarily by chiropractors but also by some medical doctors and certified physiotherapists.

Thrust manipulation is an effective method for the treatment of headaches (cervicogenic or neck generated,¹ tension,² and migraine³), post traumatic⁴ and chronic neck pain,⁵ mid-back pain,⁶ and lower back pain.^7,8 Like any true therapy, spinal manipulation is not without risk. Possible injuries with manipulation, and most contact-type therapies which involve tissue stretching and pressure, include muscle strains, ligament sprains, intervertebral disk sprains, and joint capsule sprains, and bone fractures. The incidence of these injuries is very low with the most common complaint being temporary soreness and stiffness after the first treatment,² as would be expected with any type of manual therapy.

The most serious injury associated with cervical spinal manipulative therapy is stroke caused directly by, or complications following from, the damage to the vertebral and carotid arteries of the neck which supply blood to the brain. This type of stroke is called a vertebrobasilar artery (VBA) stroke—also called vertebrobasilar stroke (VBS)—or, more generally, a cerebrovascular accident (CVA).

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Here are the current published and peer-reviewed (examined by experts in the field) facts regarding the issue of chiropractic care, cervical spine thrust manipulation, and stroke:

• VBA stroke is a very rare event. There is no difference in the risk of such an event following a visit to a chiropractor or a primary care physician (PCP). The incidence of VBA stroke associated with chiropractic or PCP visits is likely due to patients with headache or neck pain from existing VBA dissection seeking care prior to their stroke. There is no evidence of excess risk of VBA stroke associated with chiropractic care compared to PCP care.⁹ This recent large study puts to rest a similar, but seriously methodologically flawed study.¹⁰
• Motor vehicle accidents, sports, cervical spine manipulation, and many activities of daily living have been associated with injury to the arteries in the neck.^11,12,13 These injuries can, very rarely, lead to VBA stroke.
• The best information at this time indicates that the incidence of manipulation associated stroke is 1 in 400,000 to 1 in 1.3 million treatment sessions and generally acknowledged to be 1 in 1 million treatments (0.0001%).¹³ An article in the Canadian Medical Association Journal¹⁴ puts the risk at 1 in 5.85 million manipulations. There is indication that these incidences are under-reported, however, the degree is unknown. Because of the low number of incidences, the numbers are very difficult to calculate with any degree of accuracy.
• There are no clear indicators for who is at greater risk—the usual risk factors for stroke (smoking, oral contraceptives, obesity, high blood pressure, and diabetes) do not apply.¹³
• CVAs after manipulation appear to be unpredictable and should be considered an inherent, idiosyncratic, and rare complication of this treatment approach.¹⁵

The first scientific study¹⁶ of what actually happens mechanically to the vertebral artery during cervical spine manipulation was published in late 2002. The authors concluded:

1. Cervical spinal manipulative therapy resulted in strains to the vertebral artery that were almost an order of magnitude (10 times) lower than the strains required to mechanically disrupt it.
2. Under normal circumstances, a single typical (high-velocity/low-amplitude) spinal manipulative therapy thrust is very unlikely to mechanically disrupt the vertebral artery.

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In a commentary on the same article,¹⁷ the authors stated:

1. Vertebral artery elongations (lengthening, not stretching) during neck manipulations are always well within the elongations observed within the normal range of motion.
2. Vertebral artery elongations during neck manipulation are always much smaller than the elongations that cause first mechanical failure.
3. For the elongations observed during neck manipulation, there are no measurable forces (stresses) acting on the vertebral artery.

They concluded again that it was highly unlikely that a spinal manipulative treatment to the neck can cause mechanical injury to a normal vertebral artery. The authors also stated that someone severely predisposed to a vertebral artery stroke could possibly have one following manipulation; however, the same event would have also been triggered by a normal movement of the neck, for example, when turning the head while backing out of a driveway.

References

1. Nilsson N, Christensen HW et al. The Effect of Spinal Manipulation in the Treatment of Cervicogenic Headache. J Manipulative Physiol Ther. 1997;20(5):326-330.
2. Boline P, Kassak K, Bronfort G, Nelson C, Anderson A. Spinal Manipulation vs Amitriptyline for the Treatment of Chronic Tension-Type Headaches. J Manipulative Physiol Ther. 1995;18:148-154.
3. Tuchin PJ, Pollard H, Bonello R. A Randomized Controlled Trial of Chiropractic Spinal Manipulative Therapy for Migraine. J Manipulative Physiol Ther. 2000;23(2):91-95.
4. Jensen OK, Nielsen FF et al. An Open Study Comparing Manual Therapy with the use of Cold Packs in the Treatment of Post-Traumatic Headache. Cephalalgia. 1990;10:241-250.
5. Giles LGF, Muller R. Chronic Spinal Pain Syndromes: A Clinical Pilot Trial Comparing Acupuncture, a Nonsteroidal Anti-Inflammatory Drug, and Spinal Manipulation. J Manipulative Physiol Ther. 1999;22(6):376-381.
6. Schiller L. Effectiveness of spinal manipulative therapy in the treatment of mechanical thoracic spine pain: A pilot randomized clinical trial. J Manipulative Physiol Ther. 2001;24:394-401.
7. Waddell G, McIntosh A, Hutchinson A, Feder G, Lewis M. Low Back Pain Evidence Review. Royal College of General Practitioners. 1999.
8. Management of Acute Lower Back Pain - 343. The College of Physicians & Surgeons of Manitoba. 1999
9. Cassidy J, Boyle E, Cote P, He H, 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(4S) Neck Pain Task Force Supplement: S176-S183.
10. Rothwell DM, Bondy SJ, Williams JI. Chiropractic manipulation and stroke: A population-based case-control study. Stroke. 2001;32:1054-1060.
11. Rome PL. Perspective: An overview of comparative considerations of cerebrovascular accidents. Chiropractic Journal of Australia. 1999;29(3):87-102.
12. Terrett AGL. Vascular accidents from cervical spine manipulation. Journal of the Australian Chiropractic Association. 1987;17:15-24.
13. Haldeman S, Kohlbeck FJ, McGregor M. Risk Factors and Precipitating Neck Movements Causing Vertebrobasilar Artery Dissection After Cervical Trauma and Spinal Manipulation. Spine. 1999;24(8):785-794.
14. Haldeman S, Carey P, Townsend M, Papadopoulos C. Arterial dissections following cervical manipulation: the chiropractic experience. CMAJ. 2001;165 (7):905-906.
15. Haldeman S, Kohlbeck FJ, McGregor M. Unpredictability of Cerebrovascular Ischemia Associated With Cervical Spine Manipulation Therapy. Spine. 2002:27(1):49-55.
16. Symons B, Leonard T, Herzog W. Internal forces sustained by the vertebral artery during spinal manipulative therapy. J Manipulative Physiol Ther. 2002;25:504-10.
17. Herzog W, Symons B. Commentary: The mechanics of neck Manipulation with special consideration of the vertebral artery. J Can Chiropr Assoc. 2002; 46(3):135.

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