The effect of rotational head and neck movements on the afferent cerebral blood flow.

OBJECTIVE: To determine the effect of lateral rotational head and neck movements on the afferent cerebral blood flow in healthy adult humans so as to increase our knowledge of the relationship between arterial resistance and blood flow in the afferent cerebral arteries and in the arterial segments of the circle of Willis. DESIGN: Prospective, experimental study. SETTING: Department of Radiology and Department of Functional Anatomy, Utrecht University, Utrecht, The Netherlands. SUBJECTS: Nine healthy adult male human volunteers aged between 24 and 52 years participated in this study with informed consent. MAIN OUTCOME MEASURES: The changes in the afferent cerebral blood flow between the neutral (face to the front) and the rotated head positions (turn to the right and turn to the left). The relationship between the changes in the afferent cerebral blood flow and the angle of the head rotation. RESULTS: There were no significant differences between the changes in the afferent cerebral blood flow of the neutral and of the rotated head positions (p = 0.930 and p = 0.508 for the right and left head turns respectively). The correlation coefficients between the changes in the afferent cerebral blood flow and the angle of head rotation which ranged between 44.5 degrees and 72 degrees for the right turn and between 45 degrees and 72 degrees for the left turn were also not statistically significant (p = 0.191 for the right turn and p = 0.570 for the left turn). CONCLUSION: The most likely explanation for these observations was that the changes in resistance in the afferent cerebral arteries of these healthy volunteers were too small to produce significant blood flow changes. Therefore, we conclude that normal physiological lateral rotational head and neck movements do not produce any significant blood flow changes in the afferent cerebral arteries of healthy adults.