Doppler insonation of vertebral artery blood flow changes associated with cervical spine rotation: Implications for manual therapists

The controversy related to changes in vertebral artery (VA) blood flow associated with rotation of the cervical spine and the implications for professional practice is still of concern to manual therapists. The aim of this review of the literature is, first, to assess current evidence of altered VA blood flow following cervical spine rotation in persons with and without signs and symptoms of vertebrobasilar ischemia/insufficiency (VBI). Second, any reported, related alterations in blood flow that may have consequences for the individual will be discussed to assist manual therapists in pretreatment risk assessment of patients. The most commonly used noninvasive, in vivo technique for measuring blood flow is Doppler ultrasonography. Of the 88 relevant papers retrieved by a systematic literature search covering the past 50 years, 20 studies reported measurement of VA blood flow related to cervical spine rotation. A critical analysis of these reports revealed that there is no standardization of methods used (heterogeneous samples, small sample sizes, various measurement positions and instruments, and different parts of the VA measured); no consensus of findings (no change, and a significant reduction in contralateral VA blood flow, with or without VBI); and no correlations found between rotation, blood flow, and VBI. Nevertheless, this review is of value in increasing our knowledge of the possible mechanisms and consequences of repeated minor arterial trauma and of blood flow changes related to rotational movements used in cervical manual therapy. It highlights, too, the need for caution in the interpretation of pretreatment risk assessment outcome measures.