Is the risk real?

Chiropractic is the largest alternative medicine profession in the United States, and probably the most debated. Undeniably, the hottest debated topic concerning chiropractic is stroke risk. But are you really flirting with death when you visit a Chiropractor? This article, written with common argument headers, attempts to discern if cervical manipulation is a risky treatment, especially when compared with other popular treatment options.

Neck manipulation dissects the vertebral basilar artery leading to stroke…

The most basic argument that needs to be proven for anti-manipulation activists to have a ground to stand on is whether a neck manipulation has the physical means to cause a stroke. Detractors claim that forceful manipulation of the neck dissects the vertebral basilar artery, which passes through the atlas (top neck bone/vertebrae) before it enters the skull. This dissection is caused by either the physical stretching of the artery or by its contact with the bone. This very idea is actually what many chiropractic colleges teach, but its reality becomes doubtful when viewing the research.

A series of studies were conducted to determine how much force and stretch the vertebral artery can sustain before it fails. Symons study, using cadavers, applied multi-directional forces to the the neck while measuring its effects on the vertebral artery. It was determined that the arteries could withstand stretching between 132% and 160% their normal length before failing. The study was repeated utilizing cervical manipulation techniques, and it was found that the vertebral arteries were maximally stretched by 6.2% their resting length (Symons 2002). Even more interesting was although cervical manipulation is often perceived as inducing large amounts of neck rotation, due to its controlled nature the vertebral arteries are actually stretched less than in normal neck range of motion (12.5% max).

The idea that the problem is a disruption of blood flow is also not supported by the literature. Licht et al performed a study in which vascular flow was monitored pre and post adjustment. There was no difference between either groups.

Further proof that cervical manipulation is unlikely to cause vertebral artery dissection can be seen when you compare it to motor vehicle accidents. Although MVAs are a traumatic event linked to many health complications, stroke is not one of the commonly associated events. Studies measuring the force of an MVA on the neck demonstrated peak forces of about 241 Newtons, while studies focusing on forces of neck manipulation show a maximal force of 93 newtons. On top of that, rotatory forces maxed out at only 50 newtons (Haneline 2005) If the greater force seen in an MVA fails to cause strokes, why would a lower force adjustment cause it?

The number one cause of cervical arterial dissections are idiopathic. In other words, doctors have no idea what has caused it and thus it is considered spontaneous and unpredictable. Spontaneous Vertebral artery dissections occur at a frequency of about 1 per 100,000 people in the general public (Haneline 2007). Which is an eye opening statistic when the chiropractic population experiencing a CAD is believed to be about 1 per 100,000 patient, which would mean chiropractic patients are at no greater risk for stroke than the general population.

This neurology study showed that stroke occurred after adjustments…

Probably the most cited research article by neck manipulation detractors is a Canadian population based case-study by Rothwell (2001). The study demonstrated that patients who had a stroke were 5 times more likely to have seen a chiropractor within the previous week, and is a perfect example of correlation, but not causation. One key variable that the study had failed to address was why the stroke patients had visited a chiropractor in the first place. Unfortunately, many of the symptoms of a stroke are the same as the reasons people see Chiropractors: neck pain, headaches, tingling or numbness in the extremities, and occasionally mild dizziness. Strokes also present with more pathognomonic warning signs, but these signs tend to be rare, such as severe dizziness, nausea, vomiting, abnormal gait, trouble speaking, and loss of vision in one of the eyes (AHA 2009). Also, the demographic group most prone to idiopathic strokes are also the Chiropractors biggest patient base, young to middle aged women with no major health concerns.

Anti-Chiropractic bias also appears to taint many cervical adjustment articles. One key example is an article in the Journal of Neurology entitled “Vertebral Artery Dissections after chiropractic neck manipulation in Germany over three years.” Not only was this study, like Rothwell’s, a purely correlative study with no modification for external variables such as presentation, but the study’s title unfairly targets Chiropractors. Analysis of the data shows that 11% of all strokes recorded were performed by chiropractors, while 50% were performed by orthopedic surgeons and 14% by physical therapists (Rueter 2006). Even though the manipulations by MD’s and PT’s had a higher rate of associated stroke, it is the Chiropractic Adjustment that is dangerous.

Finally, recent reports have shown that an elevated incidence of stroke is seen equally in Chiropractic and medical physician offices (Cassidy 2008); once again supporting the theory that patients are presenting with a stroke, and not that DC’s, or MD’s for that matter are causing a stroke.

A signature isn't enough.

Chiropractors don’t inform patients of the risk…

A rare valid argument. Some chiropractors do not inform patients that there is a risk for stroke, others do have it written in their informed consents but fail to verbally state it (who reads those things anyway?) Legally, Chiropractors are not required to inform patients of the risk for stroke because the odds of one are so low. However, informed consent should not merely be a Risk Ratio, but also a Perceived Risk-Ratio (Ziker 2003). Since the risk of stroke is perceived in chiropractic, the doctors should address it, regardless if the risk is real or not.

I read a case study in which the person had a stroke…

We’ve all seen the case reports or the news stories where someone immediately suffered a stroke right after receiving an adjustment. However why the stroke happens presents us with three options.

1. The doctor’s impulse caused a stroke in an otherwise healthy patient. Not possible, as the prior argument has already established.
2. The patient was a stroke waiting to happen. The adjustment was the final straw. This is the most likely situation. As noted prior many patients who are currently in a stroke status may visit a chiropractor for their symptoms. In this case, any minute trauma may either mobilize a clot or cause the artery to dissect. Whether or not the doctor should be held responsible in this situation really depends on the circumstances. An unfortunate reality is that there are currently no known reliable orthopedic or neurological tests for stroke (although the Newton Neurological Battery looks promising). The best tool a doctor has is a thorough complaint history and the presentation of the pathognomonic signs. When a patient presents with the hallmark red flags, the doctor should send the patient to the hospital immediately.
3. The patient suffers an idiopathic stroke unrelated to the adjustment. Pure dumb luck.

The risk outweighs the benefits…

The rate of stroke associated with cervical manipulation varies widely among the literature. Figures place the occurrence at as often as 1 in 400,000 cervical adjustments (Dvorak, 1985) and up to 1 in 5,850,000 cervical adjustments (Hosek, 1981). Currently the generally accepted odds are about 1 in 1,000,000 to 3,000,000 cervical adjustments (Lauretti 1997); the RAND report, which is the document most federal mandates concerning chiropractic effectiveness is based upon, also puts the risk at about 1 in a million. However, there is an inherent problem within all manipulation risk studies, in that they are based on correlations, and none are experimental or direct causation models. One of the oldest tenets of research is that correlation does not equal causation. For example, there are an increase in armed robberies when ice cream sales increase. Of course its ludicrous to say that ice cream cause robberies, and instead there must be other variables in play. In this case, robberies increase during the summer, which is the same time ice cream sales increase.

For the sake of our argument, we will be using the 1 in 1,000,000 estimate, and I will compare it to the serious risks associated with other common treatments for neck pain and neck related conditions, all of which are considered safe alternatives. Serious risks are defined as those requiring medical attention.

No treatment is without its risk.

NSAIDS (Aspirin, Aleve, Ibuprofen, etc…) One key meta-analysis using 18 studies published between 1990 and 1999 assessed the risk of life threating upper gastric complications (bleeding, perforation, and hospitalization) when confounding variables such as age, previous complaints, and other medications were removed. It was found that individuals taking NSAIDs (ibuprofen, naproxen “Aleve”, etc…) were at a 380% increased risk of a serious upper GI complication (Hernandez 2000). Mathematically, if you take NSAIDs that equates to the odds of 3500 per million of having a serious upper gastrointestinal condition.

Another study focused on the risk of selective inhibitor anti-inflammatory drugs, such as COX-2 which is designed to prevent GI complications, was analyzed for myocardial infarctions (heart attacks). It was found the relative risk for these drugs are 24% higher than the standard population (Levesque 2005). Adding fuel to the fire, and resulting in the lost license of two major NSAID medications, a Medicare database study after removing most confounding variables, determined that serious cardiovascular complications resulted about 4.1% of the time when taking NSAIDS, including Aspirin (Solomon 2008). What are serious cardiovascular complications? Heart attack, stroke, congestive heart failure, and death. Other studies take these findings ever further claiming drugs such as aspirin, may actually increase the risk of heart attack up to 71%, with an average risk of about 12% (EULAR 2005). Taking the average, this could mean that an additional 570 people suffer NSAID induced heart attacks a year.

Acetaminophen (Tylenol, Excedrin, etc…) The good news with Tylenol is that it is not associated with cardiovascular or gastrointestinal disorders. However, that doesn’t mean its off the hook. Acetaminophen is associated with liver damage, and according to the FDA it is the number 1 cause of acute liver failure in the United States. Usually this is associated with over-dosage, but even minimal usage over the recommend dose is associated with death. This is especially a concern because many people will double or triple their dosages when they are in a lot of pain. Acetaminophen is the cause of 56,000 emergency room visits and 458 deaths a year (FDA 2009). The drug has also been indicated in kidney failure, as an article published in the New England Journal of Medicine determined that regular acetaminophen or aspirin usage put users at 2.5 times the risk for kidney failure, or 250% (Fored 2001). The general public sees about 1550 per million in end stage kidney failure, so if you overuse Tylenol, your odds become 3875 per million. In all fairness, this was a correlative study, not causative. (Coresh 2007)

Neck Surgery Neck and arm pain, tingling, and numbness are often the result of cervical disk herniations, stenosis, and spondylosis; all conditions that are treated with chiropractic. However, if diagnosed in an allopathic office, patients are often recommended for surgery. Although frequently uneventful, surgery obviously has its own risks. One study assessed the complication rate of cervical spine fusion for primarily the noted above conditions (Wang 2007). It was found that 0.83% of all surgeries are associated with a serious complication: Cord injury, artery dissection, infection, cardiovascular comprise, respiratory distress, nerve damage, and death. Therefore, for every 1 million cervical fusion surgeries, 8300 result in serious complications . Once again in all fairness, surgery will often involve the most serious cases and therefore their odds for complication should be elevated.

Physical Therapy & Exercise Serious complications associated with physical therapy are almost as difficult to determine as they are in chiropractic care. Most likely stroke risk matches that of the general population and initial cardiovascular risk may be somewhat increased due to increased physical load, but should decrease over extended treatments due to improving physical health.

Table 1

Conclusions

Compared to the risks associated with the most commonly used treatments for neck pain, it becomes clear that chiropractic neck adjustments are at the very least, comparatively safe. In fact, you are more likely  to die while driving to the doctor’s office in an auto accident than at the hands of the doctor. Furthermore, current research fails to even demonstrate a physiological or anatomical means for a chiropractic adjustment to induce a stroke in healthy patients. Therefore research and debate should begin to move away from attempting to determine if adjustments are safe, and move towards ways to increase the effectiveness of adjustments and improved methods of detecting the small at risk populations.

In closing, a little perspective…

By Kristopher Robert Schuster, D.C., B.S.

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References

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