What Kind of Stroke?
Chiropractic care has been reported to damage the vertebrobasilar arteries, sometimes called the vertebral arteries. The loss of blood flow to the brain resulting from this damage is called a vertebrobasilar artery (VBA) stroke. The rare incidents of VBA stroke reportedly related to chiropractic care have received special publicity. Some uninformed people claim that chiropractors cause strokes. Let us examine this issue further.
How Frequent is VBA Stroke?
Most VBA strokes are spontaneous and can be caused by car crashes, checking the blind spot while driving, and working overhead. Risk factors for VBA stroke include high blood pressure, atherosclerosis, and disorders affecting the integrity of blood vessels, among other conditions. The best estimate of frequency of VBA stroke is 0.001-0.003 percent. Between 1934 and 1994, Terrett (1996) found 183 case reports of VBA stroke after chiropractic care. Forty-two cases resulted in complete or almost complete recovery. Of the 33 cases resulting in death, 12 were attributed to chiropractor, 5 to chiropractic, and most of the remainder to medical doctors and osteopaths. With data this sparse covering a 60-year span, the estimates of VBA stroke following chiropractic care range from 1 in 400,000 to 1 in 1 million.
The most recent research on this issue was published in Spine journal in 2008. Over a nine-year period, 818 VBA strokes were treated in Ontario hospitals. The researchers found no excess risk of VBA stroke associated with chiropractic care compared to primary care (Cassidy et al., 2008). Headaches and neck pain are the early symptoms of VBA damage in eighty percent of cases. The authors suggest that people with undiagnosed VBA damage are seeking care before having a VBA stroke. In other words, saying that chiropractors cause strokes is like saying that hospitals cause heart attacks.
Researchers at the University of Calgary used unembalmed cadavers to measure the force applied during chiropractic care. They compared these forces to what was required to cause damage to the vertebral arteries. They found that the force needed to damage the vertebral arteries was about 10 times what was measured in a typical chiropractic adjustment to the upper neck (Symons et al., 2002).
As we can see, the risk of VBA stroke following chiropractic care is extremely small. It is worth noting that the malpractice insurance premium for a newly licensed chiropractor is less than $500 per year. If someone makes false statements about the supposed dangers of chiropractic, please share this information with them.
- Cassidy, David J., et al. 2008. Risk of vertebrobasilar stroke and chiropractic care: results of a population-based case-control and case-crossover study. Spine 33(4S): S176-S183.
- Symons, Bruce P., et al. 2002. Internal forces sustained by the vertebral artery during spinal manipulative therapy. Journal of Manipulative and Physiological Therapeutics 25:504-510.
- Terrett, Allan G.J. 1996. Malpractice Avoidance for Chiropractors: Vertebrobasilar Stroke Following Manipulation. Des Moines, IA: National Chiropractic Mutual Insurance Company.