Abstract
Introduction:
Extracranial atherosclerotic stenosis of the vertebral artery occurs characteristically at the vertebral artery origin (VAo) and is an important cause of posterior circulation stroke. The proximal segment of the vertebral artery is technically difficult to insonate. Only a few studies have reported on the prevalence of VAo disease in patients with stroke and little is known about its prevalence in non-hospitalized populations. Our objective was to determine the prevalence of VAo stenosis in subjects referred for outpatient extracranial ultrasonography.
Methods:
All studies performed in an outpatient neurosonology laboratory, affiliated with an academic medical center were retrospectively reviewed for VAo stenosis. The proximal vertebral segments were insonated following a standard protocol. VAo stenosis was diagnosed if the peak systolic velocity (PSV) > 114cm/sec, according to previously validated criteria. We also considered the VAo to be occluded if no flow signal could be found in any of its pre-and intraforaminal segments. Studies were also analyzed for internal carotid artery origin (ICAo) stenosis >50% to allow comparison between prevalence of carotid and VAo stenosis.
Results:
A total of 2490 subjects were available for analysis. The right and left VAo could not be insonated in18% and 25% of patients. Right-sided VAo stenosis or occlusion was present in 52/1955 (2.7%) and 74/1955 (3.9%) respectively; left-sided VAo stenosis or occlusion was present in 45/1793 (2.5%) and 64/1973 (3.6%) respectively. Overall, in those with at least one VAo insonated, 204/ 2119 (8.2%) patients had VAo stenosis or occlusion. In 29/ 2119 (1.4%), bilateral VAo stenosis or occlusion was found. Mean flow velocities were significantly lower in patients without stenosis (right 54.2±18.9 vs.149.0±57.8cm/s; left 53.5±17.5 vs.143.9±31.4cm/s). The prevalence of having either right or left ICAo stenosis or occlusion was 453/ 2401 (18.9%) and bilateral ICAo stenosis or occlusion was 112/ 2401 (4.7%). In univariate analysis, but not multivariate analysis, hypertension and diabetes were risk factors for VAo stenosis.
Conclusion:
The prevalence of VAo stenosis and occlusion was 8.2% in a diverse population of patients presenting to an ambulatory ultrasound laboratory. We found the prevalence of ICAo stenosis to be higher than VAo stenosis in the same population. Our findings contribute to the understanding of the prevalence of proximal vertebral artery disease in non-hospitalized patients.