U of T scientist: chiropractors cause strokes

Dr. John Norris, a neurologist at U of T, is calling for a ban on neck manipulations. The move is making him unpopular among chiropractors.

Norris presented his findings to the American Stroke Association last month in San Antonio, TX. By examining 156 cases of stroke caused by damage to blood vessels in the neck, Norris and his colleagues found that 39 per cent were probably caused by chiropractic neck manipulation.

Chiropractors use their hands to realign bones and tissues, which can relieve back and neck pain. But Norris is worried that when chiropractors twist a patient’s head quickly, blood vessels near the spine can be damaged. This damage often creates blood clots, which can travel into the brain and get stuck in narrow arteries.

Strokes occur when blood flow to the brain is blocked by these blood clots. They can cause minor brain damage, paralysis and sometimes death.

Chiropractors are angry at Norris’ allegations. They cite other studies that put the incidence of chiropractor-caused stroke at 1 in 3 million manipulations or less.

They point out that chiropractic manipulation is generally very safe and that other pain management treatments, like drugs, can have dangerous side effects.

One chiropractor wrote that Norris’ study was biased, calling it “junk science masquerading as research.” Norris disagrees, but says more careful studies are needed into both the benefits and dangers of chiropractic treatments. Lacking that information, patients cannot make fully informed decisions about whether to receive this kind of treatment.

Norris says the risks involved in chiropractic therapy, however minimal, are unnecessary. He acknowledges that the vast majority of therapeutic neck manipulations are harmless, but he still wants to ban the practice. Using his group’s most recent data, Norris estimates the prohibition would prevent 150 strokes in Canada each year.

Some of Norris’ critics point out that qualified chiropractors are trained to notice risk factors and will not perform risky movements when injury to the patient is likely.