Clinical Characteristics of Intracranial Reversed Vertebral Artery Flow Evaluated by Transcranial Color Flow Imaging

Background Carotid duplex ultrasonography (CUS) has been used to identify reversed vertebral artery flow (RVAF) at the extracranial cervical artery in some patients with subclavian steal syndrome. However, the characteristics of intracranial RVAF as evaluated by transcranial color flow imaging (TC-CFI), which can examine intracranial hemodynamics in a real-time and noninvasive fashion, remain unclear. The goal of this study was to analyze the prevalence of intracranial RVAF and its associated clinical characteristics. Methods Subjects were consecutive patients who underwent TC-CFI and CUS. We evaluated blood flow in both intracranial vertebral arteries (VAs) from the suboccipital echo window using TC-CFI. RVAF was defined as a flow signal directed toward the probe. We calculated the prevalence of intracranial RVAF in our subjects. Then, we investigated vascular condition (ie, site of lesion, stenosis, occlusion, and dissection) using magnetic resonance angiography, computed tomography angiography , and CUS in patients with intracranial RVAF. Results Seven hundred twenty patients (508 men; median age, 73 years) were included in this study from September 2007 to March 2013. Intracranial RVAF was seen in 12 patients (1.7%; 11 men; median age, 61 years). Among the 12 patients with intracranial RVAF, 8 patients (67%) had ischemia of the vertebrobasilar territory with distal VA occlusion, according to CUS. Of those patients, 6 (75%) had dissection of the VA. Conclusions TC-CFI detected intracranial RVAF in 1.7% of consecutive examinations in our facility. In vertebrobasilar territory stroke patients with intracranial RVAF, VA dissection may contribute to the development of stroke.