Neck Manipulation: Incidence of Vertebral Artery Dissection (VAD)

In its 110-year history, chiropractic doctors have administered millions of cervical spinal manipulations or adjustments. Today there are over 50,000 chiropractors in the United States and many thousands more in other countries. The incidents of serious complications, such as Vertebral Artery Dissection (VAD) leading to stroke that have occurred after a patient has received a chiropractic manipulation are rare. Using the data that appears in scientific literature, estimates range from one incident for every 500,000 cervical spinal manipulations to one incident for every 5 million treatments.

A Canadian study in 2001 reviewed malpractice data of all claims of stroke following chiropractic care in a ten-year period from 1988-1997 processed by the leading malpractice insurance carrier. Using extrapolated figures, it was estimated that during this period chiropractors insured by the malpractice carrier performed 135.5 million cervical spinal manipulations. There were 43 cases of neurological symptoms following cervical manipulation during this ten-year period. Of these, 20 were minor and another 23 cases were vertebral artery dissection that followed cervical manipulation.

Studies that have attempted to measure the effectiveness of chiropractic cervical spinal manipulation for neck conditions and headache, of which there have been approximately 20 randomized clinical trials (which are not retrospective, but "prospective" studies of current patients) have not reported any serious complications from cervical spinal manipulation.

VAD: Trauma-Induced or Spontaneous?
VAD can be initiated by a significant traumatic incident, such as an auto accident, a fall, or penetrating injury. In the absence of trauma, VAD is considered "spontaneous" with no known cause. However, a number of activities may precede the development of VAD. These include medical procedures such as neck extension during anesthesia or surgery and other medical risk factors. Non-medical activities that may precede the development of VAD include overhead work such as ceiling painting, nose blowing, judo, dancing, yoga, and turning the head while driving, and other daily activities. Spinal manipulation to the neck is considered one of these activities that are associated with an incident of VAD in an apparently vulnerable individual.

Patients who use oral contraceptives, have hypertension (high blood pressure) and pathologies affecting the cervical vessels appear to be associated with higher risks to VAD. An error in metabolism of a body chemical called homocysteine may weaken the structure of the cervical arteries and predispose them to damage.

Chiropractic Studies and VAD
The chiropractic profession has been very involved in studying and evaluating the risk of cervical spinal manipulation as it has been documented in the medical literature. There is some controversy as to how many incidents of VAD are associated with spinal manipulation performed by chiropractors. The problems of retrospective studies have been mentioned. Incidents in the literature regarding the connection between VAD and spinal manipulation have sometimes failed to note the small number of incidents in proportion to the number of treatments administered. Some medical commentators appear to have little understanding of what occurs in a chiropractic cervical spinal manipulation and wrongly associate the treatment with an aggressive, indiscriminate wrenching of the neck. On the contrary, chiropractors are taught precise, gentle spinal manipulation techniques in 6-8 year programs of study. Chiropractic has an extremely low rate of malpractice incidents and low malpractice rates.

VAD Screening: Need Identified
There is a small risk in vulnerable individuals when cervical spinal manipulation is performed. There are risks in all medical procedures, prescription drug use, and almost all daily activities. Further, the chiropractic profession is energetically engaged in minimizing this risk by studying ways to screen/evaluate/identify which patients are at risk for VAD in an office setting.

Bottom Line: Risks are Small
The risk of spinal manipulation to the neck is small in relation to the number of patients receiving manipulative therapy and the benefits of that therapy. It appears to primarily involve a small number of patients who are vulnerable to vertebral artery dissection. Neck manipulation most likely represents a final insult, which initiates injury to already susceptible arteries.

It is doubtful whether a neck manipulation, as it is practiced by chiropractors, would have the force to damage healthy arteries. This seems to be supported by the significant number of patients who are treated without incident. Unbiased, prospective studies with controls will yield further useful information on all aspects of cervical spinal manipulation, including the benefits and risks.