Is cervical spine rotation, as used in the standard vertebrobasilar insufficiency test, associated with a measureable change in intracranial vertebral artery blood flow?

Cervical spine rotation is used by manual therapists as a premanipulative vertebrobasilar insufficiency (VBI) test to identify patients at risk of developing VBI post-manipulation. Investigations of the effect of rotation on vertebral artery blood flow have yielded conflicting results, the validity of the test being debated. It was the aim of this study, therefore, to investigate the effects of cervical spine rotation on vertebral artery blood flow. Transcranial Doppler sonography was used to measure intracranial vertebral artery blood flow in 30 young, healthy, female subjects, with the cervical spine in the neutral position and with sustained, end-of-range rotation. Statistically significant decreases in blood flow were demonstrated with contralateral rotation particularly, in the left (45.9+/-8.5 to 41.8+/-11.6 cm/s) and right (27.8+/-6.9 to 25.2+/-8.2 cm/s) vertebral arteries. Despite this change in blood flow, signs and symptoms of VBI were not demonstrated in these subjects. Nevertheless, these findings are of clinical importance, especially in patients who may have underlying vascular pathology. Thus, this study supports the use of the VBI test, in the absence of a more specific, sensitive and valid test, to assess the adequacy of hindbrain blood supply to identify those patients who may be at risk of serious complications post-manipulation.