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 alter craniocervical arterial blood flow velocities; however, findings are conflicting. Knowledge about the effects of neck position on blood flow may assist clinicians in avoiding practices that could be dangerous. The aim of this study was 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). To accomplish this, an experimental, observational magnetic resonance imaging study was conducted. Twenty adult participants who were healthy and had a mean age of 33 years 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. The participants 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 significantly changed by any of the test positions. There wasn’t any significant difference in flow in any of the 4 arteries in any position from neutral, despite large individual variations. Only individuals who were asymptomatic were investigated, and a short section of the arteries only were imaged
The study found that blood flow to the brain doesn’t seem to be compromised by positions commonly used in manual therapy. Positions using end-range neck rotation and distraction do not seem to be more hazardous to cerebral circulation than more segmentally localized techniques.