Manual therapy of the cervical spine has sometimes been linked with serious adverse events involving compromise of the craniocervical arteries. Ultrasound studies have shown certain neck positions can change craniocervical arterial blood flow velocities, however, findings do not agree. Assuming that knowledge about the effects of neck position on blood flow may assist clinicians avoid potentially hazardous practice, the authors conducted this study to examine the effects of selected manual therapeutic interventions on blood flow in the craniocervical arteries and blood supply to the brain using magnetic resonance angiography (MRA). The study was an experimental observational MRI study. Healthy adult volunteers were imaged using MRA in the following neck positions: neutral, rotation, rotation/distraction (similar to a Cyriax manipulation), C1-C2 rotation (similar to a Maitland or osteopathic manipulation), and distraction. Twenty healthy participants with a mean age of 33 years were imaged using 3T MRA. All participants had normal vascular anatomy. Average inflow to the brain in neutral was 6.98 ml/s and was not substantially changed by any of the test positions. They observed no significant difference in flow in any of the four arteries in any position from neutral, despite large individual variations. Only healthy asymptomatic individuals were investigated and a short section of the arteries only were imaged.
The authors concluded that blood flow to the brain does not seem to be compromised by positions commonly used in manual therapy. They also said that positions using end-range neck rotation and distraction did not seem to be more dangerous to cerebral circulation than more segmentally localised techniques.