Vertebral artery ostial stenosis: prevalence by digital subtraction angiography, MR angiography, and CT angiography.

BACKGROUND AND PURPOSE (1) To determine the prevalence of vertebral arterial ostial stenosis (VOS) as determined by the “gold standard” of digital subtraction angiography (DSA). (2) To learn the correlation between vertebral ostial stenosis and study indication. (3) To determine the ability of contrast-enhanced magnetic resonance angiography (CE MRA) and computed tomographic angiography (CTA) to reflect the true prevalence of vertebral ostial stenosis as determined by DSA. METHODS Three hundred and twenty-nine patients who underwent DSA had recorded evaluation of 443 vertebral artery origins. Cases were categorized by patient age and study indication. Similar numbers of CTA and MRA studies were assessed. RESULTS The prevalence of VOS in the study population was 5.4%. VOS was not observed in patients under 40 years of age, and was seen in 12.5% of patients over 70 years. CE MRA demonstrated decreased signal at the vertebral origins consistent with stenosis in 20% of patients. CTA estimated VOS at .8%, and yielded 7.3% of studies, which were nondiagnostic for VOS. CONCLUSION The prevalence of VOS as determined by DSA is low and increases with patient age and correlates with factors such as anterior infarct (18.4%), posterior infarct (33.3%), carotid atherosclerosis (30.8%), and vertebrobasilar insufficiency (33%). Patients being evaluated for reasons less closely correlated with atherosclerotic disease, such as arteriovenous malformation (AVM) or hemorrhage showed a lower prevalence of VA stenosis (brain aneurysm or AVM 5/121, 4.1%, brain hemorrhage 5/153, 3.3%). Routine clinical MRA significantly overestimates VOS prevalence, and findings suggest that CTA underestimates the degree and prevalence of VOS.