Atypical suboccipital vertebral artery blood flow in healthy subjects: case studies using real-time ultrasound.

Manual therapists and other professionals are using real-time ultrasound increasingly to visualize vessels and determine their diameter and blood flow. Four case studies are presented to show atypical ultrasound profiles of the suboccipital vertebral artery (VA3) in healthy, young individuals. VA3 diameters and blood flow velocities were measured with the subjects sitting, and the cervical spine in the neutral position then with active, full-range rotation to the left and right. None of the subjects reported any signs or symptoms of vertebrobasilar ischemia (VBI) during the measurement procedure, despite an absence of typical VA3 ultrasound profiles on one side in two of the individuals and a decreased unilateral VA3 blood flow in the other two subjects. Possible reasons for the atypical findings are proposed. Anatomical variations of VA3 and conditions such as obesity may give rise to atypical real-time ultrasound measurements of VA3 blood flow, particularly when associated with cervical spine rotation. The possibility of altered VA3 blood flow because of such factors, which may give rise to false-positive or false-negative findings in the standard VBI test, should be considered by manual therapists in pretreatment assessments and treatment programs in professional practice.