In 2017, a piece of chiropractic research put to bed an oft-repeated misconception regarding chiropractic care and stroke. The study in question found no evidence for causation. That is, there was no convincing evidence to support the notion that chiropractic care could cause stroke.
Earlier this year, Dr Kelly Holt and colleagues produced research indicating that chiropractic care after stroke could increase strength in weak plantar flexor muscles (affected by the stroke) in patients. This gives rise to a viable line of questioning regarding whether chiropractic care might actually assist stroke recovery. Only time will tell what arises there, but it appears that conversation is not over when it comes to chiropractic and cerebrovascular conditions, and that is a very good thing.
The latest study was carried in the British Medical Journal. It was a randomised controlled trial examining cervical chiropractic adjustments and their effect on vertebral artery and cerebral haemodynamics in patients with chronic neck pain. Essentially, the study examined the question “does cervical (upper neck) manipulation increase the risk of stroke and stroke related accidents?”
Cerebral haemodynamics is essentially blood flow to and through the brain. The study also looked at cerebral perfusion, or the pressure with which oxygen saturates the brain. Both are factors to be considered in stroke risk. Hence, this study was an important one.
Researchers claimed this study was “the first to show that cervical manipulation does not result in brain perfusion changes compared with a neutral neck position or maximal neck rotation. The changes observed were found not to be clinically meaningful and suggests that cervical manipulation may not increase the risk of cerebrovascular events through a haemodynamic mechanism .”
They arrived at this conclusion by taking 20 participants and randomised them into two groups. One group undertook maximal neck rotation followed by cervical manipulation. The other had the cervical manipulation before the maximal neck rotation. The study’s participants came from a teaching clinic in Toronto and participation in the study was voluntary as long as the participants were older than 18 with chronic neck pain (without signs of major structural pathology). There were a number of exclusion criteria applied so as to ensure their existing risk of stroke was not higher than normal.
The primary outcome of the study was to measure cerebrovascular blood dynamics within the vertebral arteries and the posterior cerebrum (a specific section of the brain). Each spinal manipulation manoeuvre was followed by a comfort check (to make sure the patient was okay) and then another MRI scan. Baseline scans were taken first, before the neck rotations and cervical manipulations.
Originally, 936 patients signed up for the study. 916 of them failed pre-screening. However, statistical analysis lead the researchers to seek a sample size of 16, so the 20 participants got them well above the level needed to ascertain statistical significance.
There were obviously limitations to the study, including the length of time the effect was measured post manoeuvre. The test only covered post manoeuvre analysis as real-time analysis is challenging. So, there is still work to do.
While the statistical analysis and technical aspects of the paper are best sourced from their original location (referenced below, ), the results speak for themselves.
“We found no significant change in blood flow in the posterior cerebrum or cerebellum in chronic neck pain participants after maximum head rotation and cervical manipulation. In addition, we found no clinically meaningful changes in the blood flow or velocity in the vertebral arteries before-after head positional change and spinal manipulation. Our study adds to a growing body of knowledge regarding the impact of head position and cervical manipulation on vascular and neural activity in patients with neck pain. It is the first study to measure cerebral blood flow, vertebral artery blood flow and velocity in patients undergoing neck manipulation for neck pain. Our study does not support the hypothesis that neck manipulation or neck rotation are associated with vasospasm of the vertebral artery.”
There you have it: more evidence that chiropractic care does not cause stroke. Furthermore, chiropractors are trained to see the signs they need to watch out for that might indicate the need to call an ambulance instead of administering an adjustment. The truth is that, with chiropractors, you are in safe, trained, caring hands.
This is just a little more evidence for that.