The theory is that the force of the chiropractic manipulation can tear blood vessels leading to the brain. Vertebrobasilar stroke affects the posterior portion of the brain. Loss of blood supply to this area leading to strokes affects about 25 per cent of adults who have a stroke.
The first thing to look at is who is at increased risk for VS? Age over 70 and the presence of atherosclerosis top the list. But men and African American ethnicity raise the risk even more. These patients and anyone with diabetes, high blood pressure, or who smoke may want to check with their medical doctor first before having a manipulation of the cervical spine.
According to the World Health Organization's (WHO) Task Force on Pain, there is a link between younger age and vertebrobasilar artery stroke after chiropractic treatment. But the same association was observed in this age group receiving services from a general practitioner.
It's likely that patients with neck pain from vertebrobasilar artery problems were seeking care for their symptoms before having a stroke. The treatment may not have brought on the stroke.