A study of stroke cases led by University of California San Francisco (UCSF) neurologists, indicates that chiropractic manipulation of the neck can tear the vertebral artery leading to a stroke. The research also suggests that spinal manipulative therapy may exacerbate pre-existing vertebral artery dissections. The findings were published in the Neurology medical journal.
Several previously published studies reported cases where spinal manipulative therapy of the neck preceded a stroke by as little as minutes or as long as weeks. The current study questioned whether patients already suffering from cervical arterial dissection seek out spinal manipulative therapy from their chiropractors because of the condition’s related neck pain or whether spinal manipulative therapy itself causes dissection or exacerbates a pre-existing dissection.
The researchers reported that patients under 60-years-old who suffered strokes from tears in the vertebral artery were six times more likely to have had spinal manipulative therapy in the 30 days prior to their stroke than patients who had strokes from other causes. The patients tended to be otherwise healthier than most stroke patients and were free of risk factors including diabetes, high blood pressure, and atherosclerosis.
The researchers stress that the number of individuals who suffer stroke, regardless the cause, is just 10 per 100,000. And chiropractors perform millions of manipulations every year in the United States, so the risk is relative minute. But there is some risk of which practitioners need to be aware.
Dr. Wade S. Smith, associate professor of neurology at UCSF urges chiropractic practitioners performing spinal manipulative therapy to warn patients of the risk of cervical artery dissection. Smith also believes patients should be screened by a physician for symptoms of pre-existing vertebral arterial dissection before beginning therapy. In addition, any significant increase in neck pain or neurological symptoms within 30 days following spinal manipulative therapy should be evaluated by a doctor immediately.
The researchers were not able to determine whether specific neck manipulations cause the rare cases of vertebral arterial dissection, although other studies suggest rapid movements over short distances are safer than quick movements over long distances. If true, the researcher speculate that the vertebral artery is particularly vulnerable to mechanical dissection because it is positioned horizontally along the first cervical vertebra and therefore can be compressed when the head is extended and rotated.
A tear in the artery can cause a blood clot in the artery that blocks blood flow to the brain, leading to the neurological damage associated with stroke. But again, the risk is minimal and manipulation therapy will benefit most patients.