Changes in vertebral artery blood flow following normal rotation of the cervical spine

Extreme rotation of the cervical spine may cause compromised vertebral artery (VA) blood flow. This is of particular interest to manual therapists because of the potential risks associated with these movements. The question is whether the decreased blood flow is significant and therefore likely to cause vertebrobasilar insufficiency/ischemia (VBI) and whether contralateral and ipsilateral rotations are equally affected. Several studies measuring VA blood flow have been reported. However, different parts of the VA were studied, in small samples of normal subjects and patients over a wide range of ages. Hence, the results are controversial.

To investigate intracranial VA blood flow in normal male subjects and female subjects, aged 20 to 30 years, in neutral and maximally rotated cervical spinal positions.

Transcranial Doppler sonography was used to measure intracranial VA blood flow, with the cervical spine in neutral and then rotated maximally to the left and later to the right. The sample consisted of 60 male subjects and 60 female subjects (240 VAs). Comparisons between the neutral and rotated head positions were made within and between the groups.

There was a significant decrease (P =.001) in intracranial VA blood flow following cervical spine rotation, irrespective of side but greater on the contralateral side, in the total sample and in male subjects. Female subjects had a significantly higher blood flow than male subjects, and although they showed a significant decrease with contralateral rotation, there was no significant difference in blood flow on the ipsilateral side.

Maximal rotation of the cervical spine may significantly affect vertebral artery blood flow, particularly when used in the treatment of patients with underlying vascular pathology.