May 21, 2001 -- Do chiropractic neck treatments do more harm than good? One study finds that in people under age 45, these treatments may increase the risk of a rare type of stroke. Yet even the authors admit that the risk is small.
The group of Canadian researchers found that patients admitted to Ontario hospitals with a type of stroke called a vertebrobasilar accident, were five times more likely to have seen a chiropractor within one week before having the stroke.
"It's something to be taken seriously," says lead author Deanna M. Rothwell, MSc, a senior biostatistician at the University of Toronto Institute for Clinical Evaluative Sciences. The study appears in the current issue of the journal Stroke.
A stroke most commonly affects the side of the brain. A vertebrobasilar accident, however, occurs in the vertebral blood vessels, located at the back of the neck, and thus impacts the back of the brain. A stroke can occur when the inner lining of the artery tears -- as might happen through some type of trauma -- and a blood clot develops.
In their study, Rothwell and colleagues analyzed patient records for all of Ontario's hospitals from 1993 to 1998. They also analyzed insurance billing records to determine which patients had used chiropractic services before having the stroke.
Researchers identified 582 people who had been admitted to hospitals with vertebrobasilar stroke and compared them with 2,328 people from Ontario's general population who had no history of stroke. They found that nine of the 582 stroke patients had undergone a neck manipulation within one week of their stroke; six of those nine were younger than 45.
"That's a statistically significant finding," Rothwell tells WebMD.
However, Rothwell cautions, her data is somewhat limited because it relies on hospital records, which could contain errors.
In addition, she says, "We don't actually know that spinal manipulation was performed during the chiropractic visit. It's quite possible to go in with a neck complaint and not have a manipulation done. Some patients go to a chiropractor without a neck complaint and have a neck manipulation done."
In fact, she tells WebMD, it's not possible to know if the chiropractic manipulation actually caused the VBA. "We can only infer based on the timing of events," she says.
"This is not a public health problem," says William J. Powers, MD, professor of neurology at Washington University School of Medicine in St. Louis.
"There's always the possibility that something else -- some other trauma to the neck -- could have caused the pain and the [injured artery] -- and that's what sent them to the chiropractor," Powers tells WebMD. Whiplash from a car accident can cause similar trauma to arteries, for instance.
"In many cases, there is no history of trauma at all," he says. "In others, something mild may have happened, but the blood vessel was already weakened."
What Rothwell and colleagues actually found, says Powers, "is over a period of six years -- in all of Ontario -- six patients under age 45 who had chiropractic manipulation within one week of stroke. So this is very, very rare; it causes very few strokes. If you get your neck manipulated, your chances are very, very low of getting it ... but still, about five times higher than if you didn't."
Powers says that for years he has advised against chiropractic manipulation.
"When people ask me, I specifically say that it's OK to get your lower back manipulated, but don't let them mess with your neck," she tells WebMD.
"The type of data Rothwell used is not the most reliable, says Larry Goldstein, MD, director of the Stroke Center at Duke University in Durham, N.C.
"It can only show that visits to the chiropractor and this type of stroke are associated, not that the one causes the other," he tells WebMD. "We've all seen patients who have had neck manipulations and minor neck trauma or no neck trauma that have developed ... stroke. They're reporting that there seems to be a relationship between recent manipulation and stroke. Even with that though, the overall risk appears to be somewhat low -- 1.3 cases per 100,000 under age 45 receiving chiropractic manipulation -- that's pretty low."
So what's a tolerable risk?
"It has to be balanced by benefit," says Goldstein. "If there's no benefit, then any risk is not worthwhile. On the other hand, if there is benefit, then we tolerate various levels of risk. Medical therapies are not risk-free. What this does is raise the issue that there is this potential risk, and like anything else we do in medicine, patients need to know about that risk."
Leaders in the chiropractic community take issue with the findings -- and the implications.
"[Rothwell's study] is a deliberate and unethical scare tactic that does not stand up to critical analysis," says Terry A. Rondberg, DC, president of the World Chiropractic Alliance.
"This is pure conjecture," Rondberg tells WebMD. "I see this, frankly, as an attempt to discredit chiropractic and discourage people from seeking the care of doctors of [chiropractic].
"Chiropractors are trained to deliver a chiropractic adjustment," he continues. "Manipulation is not something we do. Manipulation is the forceful passive movement of a joint beyond its active limit of motion. ... It's not synonymous with chiropractic adjustment. And these cases of spinal manipulation are often performed by nonchiropractic practitioners like osteopaths and physiatrists."
As pointed out in Rothwell's study, says Rondberg, the rate of stroke is estimated at 1.3 incidents per one million adjustments given. "Other studies, including one covering a 28-year period reviewing 110 million chiropractic visits, showed conclusively that the risk of stroke from chiropractic adjustments is so small that it's statistically insignificant," he says.
Bottom-line message, says Rothwell: "Any medical procedure has risk associated with it. Consumers should strive to be informed and be aware of risks and benefits and talk to their health practitioners. It's also the duty of chiropractors to inform their patients about the risk."
The findings from her study should compel "the chiropractic community to produce rigorous studies to define the actual benefits of neck manipulation," Rothwell tells WebMD. "There is some research that shows it's beneficial in the short term, but there's not a lot of rigorous research to show benefits."