Dr. Vic Weatherall
Updated May 2015
High-velocity, low amplitude (HVLA) thrust spinal joint 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 generated1 and migraine2), post traumatic3 and chronic neck pain,4 mid-back pain,5 and lower back pain.6,7 As for 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, as would be expected with any type of manual therapy.
The most serious injury associated with cervical manipulative therapy (CMT) 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).
Here are the current published and peer-reviewed (examined by experts in the field) facts regarding the issue of cervical spinal manipulation and stroke:
- A 2014 review the current state of evidence on the diagnosis and management of cervical artery dissection (CD) and their statistical association with CMT states this injury is most prevalent in the upper cervical spine and can involve the internal carotid artery (ICA) or vertebral artery (VA). Disability levels vary among CD patients with many having good outcomes, but serious neurologic injury can occur. Clinical reports suggest that mechanical forces play a role in a considerable number of CDs, and population controlled studies have found an association of unclear etiology between CMT and VAD (vertebral artery dissection) stroke in young patients. Although the incidence of CD in CMT patients is probably low, and causality difficult to prove, practitioners should both strongly consider the possibility of CD and inform patients of the statistical association between CD and CMT, prior to performing manipulation of the cervical spine.8 See the article Informed consent to treatment.
- 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 large study contrasts with similar, but methodologically flawed study.10
- Current biomechanical evidence is insufficient to establish the claim that spinal manipulation causes CD, including data from a canine model showing no significant changes in VA lesions before and after cervical manipulation.8
- 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.
- Authors of a 2014 systematic review of the association between CMT and CAD were unable to find any epidemiologic studies that measured the incidence of CMT and ICA dissection. Similarly, no studies that determined whether cervical spine manipulation is associated with ICA dissection were found. The authors concluded that the incidence of ICA dissection after CMT is unknown. In addition, the relative risk of ICA dissection after cervical spine manipulation compared with other health care interventions for neck pain, back pain, or headache is also unknown. Although several case reports and case series raised the hypothesis of an association, no epidemiologic studies to validate this hypothesis were found in the review.14
- 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:
- 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.
- Under normal circumstances, a single typical (high-velocity/low-amplitude) spinal manipulative therapy thrust is very unlikely to mechanically disrupt the vertebral artery.
In a commentary on the same article,17 the authors stated:
- Vertebral artery elongations (lengthening, not stretching) during neck manipulations are always well within the elongations observed within the normal range of motion.
- Vertebral artery elongations during neck manipulation are always much smaller than the elongations that cause first mechanical failure.
- 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.
It is imperative that all health care practitioners obtain their patients’ informed consent (in all of it’s aspects) prior to performing health care interventions.
- 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.
- 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.
- 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.
- 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.
- 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.
- Waddell G, McIntosh A, Hutchinson A, Feder G, Lewis M. Low Back Pain Evidence Review. Royal College of General Practitioners. 1999.
- Management of Acute Lower Back Pain – 343. The College of Physicians & Surgeons of Manitoba. 1999.
- Biller J et al. AHA/ASA Scientific Statement: Cervical Arterial Dissections and Association With Cervical Manipulative Therapy. Stroke. 2014;45:00-00.
- 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.
- Rothwell DM, Bondy SJ, Williams JI. Chiropractic manipulation and stroke: A population-based case-control study. Stroke. 2001;32:1054-1060.
- Rome PL. Perspective: An overview of comparative considerations of cerebrovascular accidents. Chiropractic Journal of Australia. 1999;29(3):87-102.
- Terrett AGL. Vascular accidents from cervical spine manipulation. Journal of the Australian Chiropractic Association. 1987;17:15-24.
- 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.
- Chung CL, Côté P, Stern P, and L’espérance G. The Association Between Cervical Spine Manipulation and Carotid Artery Dissection: A Systematic Review of the Literature. J Manipulative Physiol Ther. 2014 Jan 3. pii: S0161-4754.
- Haldeman S, Kohlbeck FJ, McGregor M. Unpredictability of Cerebrovascular Ischemia Associated With Cervical Spine Manipulation Therapy. Spine. 2002:27(1):49-55.
- 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.
- 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.