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Chiropractic Neck Treatments Increase Risk of Stroke

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."