Imaging of vertebral artery stenosis: a systematic review

Background and purpose: Posterior circulation stroke accounts for 20% of ischaemic strokes. Recent data suggest that the early stroke recurrence risk is high and comparable with carotid artery disease. Vertebral artery stenosis accounts for approximately 20% of posterior circulation stroke, and with endovascular treatment available accurate diagnostic imaging is important. We performed a systematic literature review to validate the accuracy of the non-invasive imaging techniques Duplex ultrasound (DUS), magnetic resonance angiography (MRA) and computed tomographic angiography (CTA) in detecting severe vertebral artery stenosis, with intra-arterial angiography (IAA) as the reference standard. Methods: We identified studies that used non-invasive imaging and IAA as the reference standard to determine vertebral artery stenosis and provided adequate data to calculate sensitivity and specificity. We analysed the quality of these studies, looked for evidence of heterogeneity and performed subgroup analysis for different degrees of stenosis. Results: 11 studies categorised stenosis into 50-99%. The sensitivity of CTA ( single study) and pooled sensitivities of contrast enhanced MRA (CE-MRA) and colour duplex were 100% (95% CI 15.8 to 100), 93.9% (79.8 to 99.3) and 70.2% (54.2 to 83.3), respectively. The specificities for CTA, CE-MRA and colour duplex were 95.2% (83.8 to 99.4), 94.8% (91.1 to 97.3) and 97.7% (95.2 to 99.1). However, specificities for CE-MRA and colour duplex demonstrated significant heterogeneity (p = 0.003 and p = 0.002, respectively). Conclusions: CE-MRA and possibly CTA may be more sensitive in diagnosing vertebral artery stenosis than DUS. However, data are limited and further high quality studies comparing DUS, MRA and CTA with IAA are required.