Chiropractic and Stroke

(Originally posted on bcotoronto.com on Nov 24th, 2011)

Vertebral ArteryThe most publicly debated and most dangerous risk of chiropractic is stroke. This risk stems from the anatomy of the neck, or “Cervical Spine”. An addition to the basic structure of the spine, which we have discussed several times previously, is a series of holes in the side projections of the cervical vertebrae which create a tunnel on either side of the spine. Through these tunnels run arteries that lead up into the skull and supply our brains with blood. They are called the “Vertebral Arteries”. The path of the arteries becomes very twisted from the second cervical vertebra (second from the top) all the way into the skull as the top most vertebra is wider than the others. These two arteries make up half of the blood supply to the brain and so are very important.

When the blood flow to the brain is compromised this can cause a stroke. This can happen two ways: if there is a clot, and if there is a bleed in the arteries, both of which decrease the blood to the brain and thus deprive the brain of oxygen. The clotting conditions are the most concerning with chiropractic adjustments. This is due to the movement of the artery with the movement of the vertebrae. When we turn our necks the vertebrae follow that motion one by one, starting at the top. This means that extra wide first vertebra twists before the second one does and puts tension on the artery. Now if you tilt your head back this, again, starts to tilt each vertebra back one by one. This puts the artery in the back corner under tension and compression. This normally does not pose a problem unless the twin artery on the other side has a clot in it and has decreased blood flow already. This then takes a 25% loss in blood flow, which the body is built to be able to handle for short periods of time, into something closer to 30 or 50% loss (depending on the size of the clot).

This is highly unfortunate, as this is the most common movement for a chiropractic adjustment of the upper cervical spine (the region of the spine involving the upper three vertebrae). Another fear within the medical community is that with an adjustment a piece of a non-problematic clot lower in the arteries could break off and travel into the smaller blood vessels in the brain and cause a complete blockage there and thus a stroke.

With these points in mind let’s look at the research around chiropractic and strokes. The original research linking chiropractic and strokes was a survey of patients and their families who had suffered from a stroke. They were asked if they had seen a chiropractor within the last 30 days. Initially this may not seem odd but when you critically analyze this, the blood travels through the circulatory system very quickly and a single cell will circumnavigate the entire body several times in a few hours let alone in a day. So it is physiologically improbable that a clot dislodged from a chiropractic adjustment would take longer than several minutes to travel from the neck into the brain.

I am in no way claiming that this proves that chiropractic manipulations cannot cause strokes but that they are over reported which is supported by Rothwell, Bondy, and Williams’ article in 20011. They go on to assert that the rarity is so low that it is extremely difficult to calculate a proper statistical risk1. Meeker and Haldman agreed with this after reviewing more than 160 reviews in the literature in 20022. They even went so far as to claim that the estimated risk of stroke with chiropractic manipulation is smaller than that associated with many commonly used diagnostic tests or prescription drugs2.

In 2008, Dr. David Cassidy published one study comparing the rate of occurrence of stroke for chiropractors and general practitioners (family doctors) in Ontario3, and in Ontario and Saskatchewan combined4. He showed that there is a statistical association between chiropractic care for neck or head conditions but also an equivalent association between medical treatments for neck or head complaints3. The second study showed that the annual rate of strokes among the general population of both provinces was not related to the rate of chiropractic use4. This suggests that it is more likely patients are coming to the chiropractor or the medical doctor already experiencing the initial signs and symptoms of a stroke and subsequently progressing to a full blown stroke soon after visiting either doctor.

It is very important to understand the signs and symptoms of a stroke so that you can make sure you and your loved ones can receive the appropriate care. The most important and most common symptom is a massive headache, usually described as the worst headache of your life. This is what the medical community calls a red flag, especially if it is a throbbing and/or sudden headache. Other major symptoms are slurred speech, and difficulty voluntarily controlling facial muscles and one half of your body. These are commonly remembered as S.T.R. as in the first three letters of the word STROKE. S for SMILE, seeing if both sides of your mouth rise the same. T for TALK. And R is for RAISE your arms to see if they move at the same speed and to the same height.

If you think you or a loved one is having a stroke, the appropriate place to go to is the emergency room. They have the necessary equipment and training to take care of you and save your life.

Thanks for reading,

Dr. Ben

P.S. – This is a very important topic in health and it is a key issue in chiropractic. Please ask any questions you have here or e-mail me at dr.ben@bcotoronto.com

1. Rothwell DM, Bondy SJ, and Williams JI. Chiropractic Manipulation and Stroke: A Population-Based Case-Control Study. Stroke 2001 32:1054-60

2. Meeker WC, and Haldeman S. Chiropractic: A Profession at the Crossroads of Mainstream and Alternative Medicine. Annals of Internal Medicine 2002 136(3): 216-27

3. Cassidy JD, Boyle E, Côté P, He Y, Hogg-Johnson S, Silver FL, and Bondy SJ. Risk of Vertebrobasilar Stroke and Chiropractic Care: Results of a Population-Based Case-Control and Case-Crossover Study. Spine 2008 33(4 Suppl):S176-83.

4. Boyle E, Cote P, Grier AR, and Cassidy JD. Examining Vertebrobasilar Artery Stroke in Two Canadian Provinces. Spine 2008 33(4 Suppl):S170-5.

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