In 1983, one study suggested there are two to three serious incidents involving the vertebrobasilar system in one million manipulations. This would mean that currently there are 200 to 300 serious incidents involving the vertebrobasilar system each year. A more recent study in Canada found that the risk of a vertebrobasilar injury from cervical manipulation may be as high as 1.3 incidents per 100,000 cervical manipulations. This would mean that currently there are 1,300 people seriously injured each year through cervical manipulation. An even higher incident rate was found in a March 2001 study, in the New England Journal of Medicine, which estimated that the incidence of vertebral or carotid artery dissections may even be as high as one incident per 20,000 cervical manipulations.

A 2010 study of deaths after spinal manipulation found 26 published cases, and seven unpublished ones, mostly due to a tear, or “dissection of a vertebral artery,” and suggested that many more cases had not been reported. A 2007 survey of adverse effects published in medical journals between 2001 and 2006 found that “spinal manipulation, particularly when performed on the upper spine, is frequently associated with mild to moderate adverse effects. It can also result in serious complications such as vertebral artery dissection followed by stroke.” It noted that “survey data indicated that even serious adverse effects are rarely reported in the medical literature.” A 2013 survey of 43 studies conducted between 2001 and 2011 found 707 incidents of stroke associated with cervical spinal manipulation therapy, but the authors said that understanding such incidents was hampered by inadequate reporting.

Felipe Albuquerque, a neurosurgeon in Phoenix has stated, ““The epidemiology of these injuries is almost impossible to ascertain,” Albuquerque and others wrote in a 2011 study in the journal Neurosurgery. “Studies suggest their incidence to be between 1 in 100,000 and 1 in 6,000,000 manipulations. Given that Americans visit chiropractors more than 250,000,000 times per year and that 30 percent of these visits involve cervical manipulation, the incidence of arterial dissection is likely to be higher than the lowest estimates. A significant number of dissections may go unreported either because they are mild or asymptomatic.”

In February of 2016, Katie May, a well-known model, died. The L.A. County Coroner’s office found the cause of death was an injury during “neck manipulation by chiropractor.” In this specific case, the neck adjustment caused a cervical artery dissection (CD). This occurs when a trauma, like a neck manipulation (aka cervical manipulation), causes a small tear in the layers of artery walls in the neck. A 2014 statement from the American Heart Association states that, “[i]t can result in ischemic stroke if a blood clot forms after a trivial or major trauma in the neck and later causes blockage of a blood vessel in the brain. Cervical artery dissection is an important cause of stroke in young and middle-aged adults.”

There are many high risk categories for cervical manipulation. Please make sure your chiropractor does a proper history prior to any cervical manipulation. And, call 911 if you have severe headache, neck pain or cervical muscle spasms after a cervical manipulation.