Dr. Kevin Leach:  There’s a big stigma that chiropractors cause stroke and that it might even be a common thing but this research review says it’s actually extremely rare if it actually happens. Hi there, I’m Dr. Kevin Leach here with The Chiropractic Deep Dive Podcast bringing you the most important research and information on conservative primary spine care upper cervical chiropractic care and traditional chiropractic care. These research reviews, interviews, and episodes are made for you whether you’re a medical doctor, patient or concerned family member or friend. The goal of these shows is to bring awareness of the importance of taking care of our spine and the impact it has on our health and the hundreds of different health conditions it could cause without us realizing it. I’m really trying to bring value with these so I’d appreciate commenting on the videos, hitting the like button and sharing them with as many people as you can. You never know who might need to see it and consider subscribing to the channel so you can see all the other episodes and videos coming out. Thank you so so much, I truly appreciate your support. Now onto the show. Welcome everyone to The Chiropractic Deep Dive Podcast and The Chiropractic Research Show. This is episode Number One and the first show of the series to start off the show on chiropractic and stroke. Again, I’m Dr. Kevin Leach. I’m here once again with my good friend and colleague Dr. Tyler Evans. How are you sir? 

Dr. Tyler Evens:  Good to see you. 

Dr. Leach:  Awesome, this is going to be a good and important podcast. So we have in our profession Dr. Gerry Clum is a very well respected chiropractor in our profession. He’s done a tremendous amount for our profession. He’s done several presentations on chiropractic and stroke and so what I did was I grabbed one of these presentations that he did and he mentions ten different research papers in there to support you know, evidence against chiropractors causing stroke. And again we’re not saying that it’s never happened but we do realize because we hear it from patients we hear it from colleagues that there’s a stigma that it’s a lot more common than it most likely is in and in real, not in fact, but in most likely it’s much more rare than public knowledge kind of thinks or public perception seems to think. Yeah. So we reviewed all these studies so Dr. Tyler and I have these studies. I’m going to go through each one just to kind of pin just a real quick paragraph highlight of each one and we’ll do a discussion for each. For just all of them but then we’re going to actually do each paper as well individually and break it down even more. And possibly even in the future do more studies that support what we’re talking about here. But we have a lot of the main papers and again thanks to Dr. Clum because he kind of compiled all this. He put him in chronological order. He related them and how why one study came out and so I’m just going to do a quick review about that and then we’re gonna do a little discussion at the end.

Dr. Evens:   Dr. Leach, real briefly would you just, I mean I can do it or you can do it, but give a quick background on stroke in relation to the United States? Like how many strokes are there a year, how many cause death and then how many are what we’re talking about. You want to go ahead and do that? 

Dr. Leach:  Yeah. I’ve got some of the statistics here but If you’ve got a good grasp on it.

Dr. Evans:  I mean, I think if I remember it’s roughly 790,000 – 800,000 strokes a year. That includes carotid which is the large pipe up into the brain and then the vertebral artery which is a smaller pipe that goes actually through your cervical spine up and feeds the brain stem, the back of the brain. The carotid actually feeds the larger part of the brain and when there’s a carotid artery stroke usually there’s something to do with language. And then when there’s a vertebral artery basilar stroke those arteries actually go up through the upper cervical spine up into the foramen magnum, the big hole in the base of the skull and actually feed the base of the brain. And then the cranial nerves which then you’ll see problems with eye, nystagmus, and problems with vision balance things like that. So those are things that we’re looking for in our practices on a regular basis to really try to weed out – is this something that might be occurring. But it’s a very very small amount so when you talk about the vertebral artery strokes versus the carotid artery strokes what is it like, it’s like 5% of the total are vertebral artery strokes? 

Dr. Leach:  So 1 in 230 strokes. 1 in 230. So less than 99% of strokes are the vertebral..

Dr. Evans:  Oh wow. 

Dr. Leach:  ..basilar artery stroke that we’re referring to here. And I’m actually glad you brought that up because just to clarify the claim of chiropractors causing stroke is because it is a force issue. And so obviously when the vertebral artery is up here and the chiropractor even another physical therapist or osteopathic doctor doing a cervical manipulation or a chiropractic adjustment they think that the force is causing the stroke. And so a lot of this research, some of it is epidemiological, some of it is looking at actual force and geometry and blood flow in different things. And so the claim is is that the force that’s being put into the neck is causing the stroke and this is the research is seeing okay is that true is that possible is that what’s happening or is it like you said these patients are coming into the office they’re already having a cervical dissection which leads to a stroke and obviously an adjustment is not going to stop that. And so what this research looks at is, is there a causative relationship or is there an associative relationship. So is it association or causation and so that’s what Dr. Clum did. He broke all these studies down to really see what the evidence was showing and the evidence supports very strongly that if it does happen it’s extremely extremely rare and as we go through the papers here you’ll start to understand why.  

Dr. Evans:  Yeah. And it’s a thing where like I have patients that are nurses that you know they came in and they were suffering from post-concussion syndrome and other migraine issues all kinds of problems right. They get well under care but initially they’re very afraid because you know they work in a place where there’s a lot of already we call it “already always listening” there’s this already in the air kind of talk about how if someone had a stroke better ask them did they see a chiropractor right before they came in because that’s probably what caused it. And that’s real and so you know there’s a pervasive story about this and it’s been going on since I think Dr. Clum said in the video like the 70’s or 80’s that’s when that started. And back then we didn’t have the literature to refute it and now we do a lot of these papers are from 2000 and on. And so Dr. Clum does a great job and let’s get to it. 

Dr. Leach:  Awesome. So let’s just get right into it. The first paper is called “Chiropractic Manipulation and Stroke” by Rothwell et al. Published in the medical journal “The American Heart Association” and this was in 2001. And this paper was the research that led to the landmark Cassidy study in 2008 that we’re going to talk about in a moment here. So what the Rothwell study showed was that for patients under 45, patients were five times more likely to have a stroke if they visited a chiropractor prior to their stroke. Now this obviously raised a lot of ears and eyebrows saying, “Wow, like  chiropractors are causing stroke.” Now the problem with this paper is that Rothwell didn’t ask what else that patient did prior to the stroke. So what the paper showed was an association not a causation. So what they found was evidence that yes, patients were five times more likely to have a stroke if they saw a chiropractor but that just says there’s an association it doesn’t say causation. So the big question that the future research needed to attempt to answer was, “Is there evidence that chiropractors are causing stroke or is it just an association?” 

Dr. Evans:  And that leads to the Cassidy study Dr. Leach while you’re pulling that up… 

Dr. Leach:  Yeah   

Dr. Evans:  A couple of things about that Rothwell study and what they didn’t study that’s the real takeaway from that paper is okay we found this data. But they go and point directly at chiropractors and just go and make this claim that oh well chiropractors must cause stroke. When in reality they didn’t study things like were these patients smoking, were they on birth control, how many times had they been to a medical doctor. A lot of other statistics that may have affected what was actually happening right. And so it’s a story of missed data right and so it was unfortunate but then it led to all this work that these other Canadian researchers did that Cassidy et al. They really did some great work and have them to thank for that so. 

Dr. Leach:  Absolutely. Yeah absolutely.  So this paper by Cassidy “Risk of Vertebral Basilar Stroke and Chiropractic Care” This was in “The Journal Spine” again by Cassidy. Now what Cassidy did, which is why we can thank Rothwell, Cassidy grabbed Rothwell, the researchers, the medical doctors from that study.. 

Dr. Evens:  Dr. Sundi 

Dr. Leach  ..they took the data, they took the time, they took everything from that study and asked the question also what was the likelihood of those patients to see a medical doctor. Now what they found was the same risk factor meaning they were five times as likely I think actually in this one they found three times as likely for both. So I need to dig a little bit deeper in there why it went down to three compared to the five. But either way they found it was the same. Meaning patients were more likely to have a stroke if they visited a chiropractor or a medical doctor. And we know medical doctors like 99.9999% of them don’t do cervical manipulations. 

Dr. Evans:  Right

Dr. Leach:  So now we have an association, this is the big findings of the Cassidy study, we have this association of – okay these patients that are leaving are having a stroke eventually whether they see a chiropractor or whether they see a medical doctor. Now it would lead to suggest that if chiropractors were causing strokes then there would be a higher incidence of strokes from the chiropractor than the medical doctor but that’s not what they found. And this was a massive study. This was 110,000,000 patient person years.. 

Dr. Evans:  Right 

Dr. Leach:  ..under over like 10 years like it was a massive pool of epidemiological study looking at that. And so that was a huge – that was a huge finding with that cast the first Cassidy study in 2008. Any comments on that one? 

Dr. Evans:  Yeah. Just that that was on the vertebral artery. Exactly. Exactly. Because the one in the future I’ll mention in a second here was for vertebral and carotid. And so just to kind of review again we talk about cervical arteries. There’s cervical arteries and then there’s the carotid and the vertebral. And like Dr. Evans said before carotid’s in the front is 80% of the blood flow and then the vertebral is 20% in the back. And again the chiropractors are accused of causing the vertebral artery one because it’s close to the atlas bone and it can be stretched and a lot of force on there so that’s what the claim is again. All right so next study is “Chiropractic Care and the Risk of Vertebral Stroke” by Koslov, et al published in “The Chiropractic and Manual Therapies Journal.” The purpose was to repeat the Cassidy study that was done in Canada in America to see what the claim was. And what they found was even better than the Cassidy study. That not only – so just to review just to repeat one more time here, the Cassidy study showed no increased risk of stroke by seeing a chiropractor or medical doctor. There was an increased risk by seeing either one of them but no increased by the chiropractor. What the Koslov study is showing is that there was no association between vertebral basilar stroke and chiropractic care regardless of the age group. And because actually the Canadian study was below 45 and there was no excess risk above the age of 45 and I know you’ve got some thoughts on that as far as why – you know why that could be as far as under the age of 45. But maybe we’ll get into that in a little bit here. Next study is “Systemic Review and Meta-analysis of Chiropractic Care and Cervical Artery Dissection: No Evidence for Causation.” That’s in the title that’s a huge – typically findings aren’t put in the title you know this one was put in the title. 

Dr. Evans:  And just defining causation and correlation you know causation is one plus one equals two. 

Dr. Leach:  Right. 

Dr. Evans:  Correlation is one and then one over here and there might be a two somewhere in around but it’s not an algebraic equation. 

Dr. Leach:  Right. Right. And so this one was by Church, et al published in “The Journal Cureus” and the importance of this study was this was done by neurosurgeons. So this wasn’t even done by chiropractors. This was done by neurosurgeons and they found again no evidence for causation. The next study was again done by Cassidy and I think this one was done in like 2016 or something and this is “Risk of Carotid Stroke After Chiropractic Care: A Population-Based Case Crossover” study published in “The Medical Journal Stroke.” So I don’t think the other one was published in a medical journal this one was published in a medical journal and they did vertebral and carotid. And they found the exact same thing with the vertebral – with the carotids as they found with the vertebral. And I think it’s really important to again emphasize it’s always been the claim that chiropractors are causing the stroke because of the pressure put on the vertebral artery or vertebrobasilar artery not the carotids. Is that correct? 

Dr. Evans:  I would say that anyone that knows the literature and understands anatomy and physiology would not put blame on chiropractors for the carotid 

Dr. Leach:  the carotid 

Dr. Evans:  being so far away. However, I’m sure over time that that has happened it has come up. 

Dr. Leach:  Yeah. Well and the point that I was trying to say is that if they found the exact same thing with the carotids. So again just like the association of chiropractors and medical doctors if we have the same thing from the vertebrals and carotids then it’s like well there doesn’t seem to be a causative factor or evidence for a causative factor to be claimed there. 

Dr. Evans:  Right 

Dr. Leach:  Okay the sixth paper reason Dr. Clum obviously talks about all this. He talks about a paper that Koslov referenced in his paper “Cervical Arterial Dissection and Association with Cervical Manipulative Therapy.” This was by Biller published in “The American Heart Association.” Now the big finding here was that again the medical journal medical association concluding that there is no causal relationship. So again the medical profession – the medical profession is saying that there’s no causal relationship here. So. But they would still recommend an informed consent because they say that there’s no causal relationship but they’re saying they’re still open to the potential that it may have and it could be very rare. And again it could happen and we haven’t even touched on this with an unhealthy artery, something with the dysplasia, the marfan syndrome, or some sort of connective tissue type disorder. 

Dr. Evans:  Yeah

Dr. Leach:   In that case a chiropractic adjustment could actually potentially cause something like that but there’s no evidence that’s been found in a healthy individual that would cause this. 

Dr. Evans:  When it comes down to it when you look at chiropractic malpractice insurance versus medical malpractice insurance, the insurance companies know who has more lawsuits filed against them, big ones. So again being generous and being kind I think it’s important to just put it in perspective right and that the risk and the informed consent paperwork the risk that you’re taking on and signing that informed consent paperwork or as a chiropractor having that informed consent paperwork it is not a plea of guilty. 

Dr. Leach: It’s exactly what informed consent is. It is that this has been claimed. There’s an association there. It’s a possibility even though it’s extremely rare. That’s what informed consent is. 

Dr. Evans:  Yeah. Malpractice insurance for the medical field is ten times higher than what it is for a chiropractor and absolutely that’s clear in the data. So if there really were a huge problem here the malpractice would reflect that. 

Dr. Leach:  Absolutely. Absolutely. Cool. So we’re getting into those papers now that focus more on the mechanisms of injury. So the ones that we just did were more epidemiological meaning they’re looking at populations and they’re saying what’s the incidence of these things happening association, correlation, causation things. These next papers look at oh they actually studied and looked at the mechanism that’s been claimed for the manipulation to cause stroke. So this paper here is “Internal Forces Sustained by the Vertebral Artery During Spinal Manipulative Therapy” and this is by Herzog, et al published in “The Journal of Manipulative and Physiological Therapeutics.” The study was done on cadavers to test the mechanism believed to cause strokes during manipulation. Which would be the stretch force to the vertebral artery or vertebrobasilar artery during the manipulation. Now what they found was that the artery could be stretched 139% at minimum before any damage was done to it. 139% damage. They also measured how much manipulation stretched the artery. And so it was 7.5% of its length was the maximum stretch that a manipulation would cause to an artery. 7.5% for manipulation. 139% before damage was done. So the manipulation only caused 6% of the stretching that the artery could withstand before a failure. So this is a huge study and granted it was on a cadaver which isn’t a live human being but that’s what most soft tissue studies are done for so that’s kind of – I don’t know if it’s the gold standard but it’s very common. So that’s a huge study right there. 

Dr. Evans:  Definitely. Good data. Very good data. 

Now, the next one here is “Biomechanics of Vertebral Artery Segments C1 Through C6(so those are the neck bones) During Cervical Spinal Manipulation(neck manipulation)” by Herzog and Wuest.. I think that is how the name is pronounced, excuse me if I mispronounce that. This was published in “The Journal of Manipulative and Physiological Therapeutics” as well. This was done in response to critiques of the Herzog study to measure the forces at the attachment points of the arteries meaning where they were anchored. So they were saying, “Oh you’re just measuring where -not where it’s going through the transverse process, not where it’s connected to the bones.” And so they did that and not only did they find that it didn’t matter but they actually found in that study that during cervical rotation, just cervical rotation, puts more strain on the artery than the manipulation does. 

Dr. Evans:  Yep. So in an exam. 

Dr. Leach:  Well so and that’s the next study here. So this one showed that it was just cervical range.. 

Dr. Evans:  Yeah. 

Dr. Leach:  ..and I had to kind of hone in and kind of figure out what the differences were on these two studies there. But I think it’s – yeah so the next study looked at – they went into a range of motion exams. Right. So I think the first one was just rotation. They just did rotation and a manipulation. They found that the manipulation wasn’t as powerful, or strong, or as forceful. And then the next study here so “The Vertebral Artery Strains During High Speed Low Amplitude Cervical Manipulation” by Herzog in “The Journal of Electromyography and Kinesiology” the conclusion is similar to the Wuest study, “Range of motion testing forces exceeded the amount of force that during spinal manipulation.” So again the stretching forces what they’re seeing is that the manipulation is lower than just a person moving through their range of motion with their neck. So another huge finding to imply it’s not the forces aren’t enough to to really cause this damage here. 

Dr. Evans:  Yep. 

Dr. Leach:  And the last one here is an interesting one and I’d never heard of this until Dr. Clum talked about it. So there’s something called “Bernoulli’s Principle.” 

Dr. Evans:  Yep. 

Dr. Leach:  And so it’s like when you kink a hose, the pressure builds up, and then you let it go and there’s a forceful shooting out. A mechanism of causal of stroke has been said that it’s the blood shooting through and damaging the inside of the arteries. And what they did was they measured this. They measured during different positions, they measured during the adjustment, and after the adjustment. They found that there was no significant change in that velocity – of that. To again indicate there’s no change during the adjustment so that mechanism doesn’t really make sense either. And that’s it for the review here. We will have all these in the description below for links that you can go and you can get these as well. But Dr. Evans, what do you have as far as maybe discussion on any of this? 

Dr. Evans:  Yeah. I think, great job you really went through all those papers well those are the highlights. You nailed it. One of the things that Dr. Clum pointed out was just the amount of time that a correction might be or an adjustment might be. It’s about six milliseconds or something like that versus the amount of time it would be for a patient to turn their head in range of motion. It might actually be about six whole seconds. So if you talk about the differences in pressure in Bernoulli’s and in just in millimeters of mercury, or however they measure the tension, that it would be tremendously higher just in range of motion testing than it would be in a manipulation. And so that’s another point, I can’t remember which paper that was in, but I remember him talking about it. 

Dr. Leach:  Yeah I think it was the one where they did, it was the second to last one here. 

Dr. Evans:  The exam.

Dr. Leach:  Where they did the, yeah, range of motion testing forces exceed the amount of force of the artery during spinal manipulation. And again we mentioned it just in passing before but it’s important to understand that these healthy individuals. So what they found is, and I think Dr. Clum mentioned it in his presentation, I think 80% of strokes have some sort of connective tissue.. 

Dr. Evans:  Disorder. Yeah. 

Dr. Leach:  …disorder of some kind. He mentioned EDS type 6, marfan’s, fibromuscular dysplasia. I think that’s the one he said there was 80% have some sort of fibromuscular dysplasia that have stroke. So I think the main takeaway, and you said it in the very beginning, is these patients that are having a dissection, they seek medical care, whether it’s from a chiropractor from a medical doctor, and they go on a stroke. And again it’s not what the chiropractors are doing but it’s what’s walking through the door. 

Dr. Evans: What’s walking through the door. Yeah. 

Dr. Leach:  And again you can’t prove a negative by saying it’s a manipulation from a chiropractor, from osteopath, from anybody has never caused a stroke. But what the evidence is showing is that if it happens it’s extremely rare and it’s for somebody who doesn’t have healthy connective tissue and maybe has a connective tissue disorder, which actually many people don’t even know that they have. Right. 

Dr. Evans:  Right. And I believe it was that many people have strokes all the time and they aren’t diagnosed. I don’t remember the statistics on how many. Do you remember him saying that? 

Dr. Leach:  I don’t remember but yeah that’s what he was saying is that a lot of people have these dissections and they don’t even turn into a stroke they just they heal naturally. 

Dr. Evans:  Yep. Like it happens frequently and  most of the time they’re not diagnosed and they’re not recognized. And so these things are happening in nature. They’re happening in life and then to go and pin it on someone. Yeah, of course we all want to have a reason and objectively identify what caused things to happen when they go wrong. But pinning it on a treatment that is so low in… 

Dr. Leach:  Risk. 

Dr. Evans:  ..risk versus another treatment that the risk is so much higher of other problems that might incur something like cervical surgery of the spine, or lumbar surgery of the spine, or even just taking daily NSAIDs or Ibuprofen. The side effects of these medications and then you get into the side effects of other medications. The risk just mounts right and some simple things like smoking and birth control, those two things together. Those really create a big problem for those under 45. Dr. Clum talked about how as we age we actually build a protective factor into our bodies as things start to stiffen up and become harder. That could be a reason why, under 45, these people are usually on birth control and more often people under 45 would be smoking. That’s where that breaking point comes from. 

Dr. Leach:  So yeah. And again for anybody watching this, this information is really not that readily available and that’s one of the reasons why I wanted to do this and why we’re doing this. We’re trying to disseminate this information to people because chiropractic can truly help thousands and thousands. I mean it’s an incredible profession it can help people but if people have the stigma of this worry of an extremely rare event that could potentially happen to them and not get the help that they need. I mean that’s a problem. That’s a huge problem. So just awareness and some in-depth knowledge really about the risk here is super important for everybody. Just getting rid of some of the stigmas that are involved with the profession here. 

Dr. Evans:  Absolutely. Yeah. 

Dr. Leach:  Yeah. Cool. 

Dr. Evans:  Great job. 

Dr. Leach:  I’ll just link each of the studies and they’re going to go to different places. A lot of them are open access so they’re going to be free. I think some of them you have to pay for. 

Dr. Evans:  Yeah. But you can see the abstracts. 

Dr. Leach:  And you can see the abstract. Yeah. For sure. 

Dr. Evans:  And if you would, link Dr. Clum’s video in there too if you can.

Dr. Leach:  For sure. And for those listening, Dr. Clum is speaking to chiropractic students during this presentation so it’s not necessarily to the public. So just kind of keep that in mind.

Dr. Evans:  Yeah. 

Dr. Leach:  Yeah. Yeah. There might be some terminology and some things in there or some boring things that people don’t want to know. 

Dr. Evans:  Yeah. 

Dr. Leach:  But yeah. It’s absolutely an incredible presentation and he’s done a lot for the profession. We thank him very much. 

Dr. Evans:  Yeah. 

Dr Leach: Cool. All right. Anything else doc? 

Dr. Evans:  Nope. Great job. 

Dr. Leach:  Good stuff and we’ll talk to you soon. Thank you. Okay so that’s it for this episode. So what did you learn that fascinated you or surprised you about the research today? Join or start the conversation in the comments below.  Hey. Thanks so much for watching. To watch more of our research shows click or tap the screen right there to subscribe to the channel. Click or tap the screen right there. Until next time, I’m Dr. Kevin Leach with the upper cervical chiropractic research show. Bringing awareness to conservative primary spine care, upper cervical chiropractic care, and traditional chiropractic. Until next time, take care and take care of your spine. It’s the only one you’ll ever have.