Vertebral artery hypoplasia and a low velocity in the intracranial vertebrobasilar system on US might change the treatment of patients with posterior circulation infarction for primary and secondary prevention.

Aim: Unilateral vertebral artery hypoplasia is considered a risk factor for posterior circulation infarction. Despite the increasing attention on unilateral vertebral artery hypoplasia, few studies have discussed bilateral vertebral artery hypoplasia, its influence on stroke, or its collateral supply from the circle of Willis. We aimed to identify its characteristics, stroke pattern, and unique ultrasonographic and brain imaging findings.Materials and Methods: Of the 1,301 consecutive in-patients diagnosed with acute ischemic stroke from January 2013 to December 2015, medical and laboratory data and stroke or transient ischemic attack history were recorded. We enrolled patients who underwent both brain magnetic resonance imaging and sonography examinations. Vertebral artery and posterior cerebral artery analyses were conducted in accordance with clinical criteria.Results: Adequate imaging data were available for 467 patients. Of these, eight patients met the criteria for bilateral vertebral artery hypoplasia. The mean age was 62.9 ± 12.1 years. There were six male (75.0%) and two female patients (25.0%). A high prevalence of hypertension (7/8, 87.5%) was noted.Sonograms displayed a very low net flow volume in the vertebral arteries, with the average net flow volume being 28.9 ± 9.7 mL/min. A high frequency (6/8; 75.0%) of the fetal variant posterior cerebral artery from the carotids was found. The infarction patterns in these patients were all bilateral, scattered, and in multiple vascular territories.Conclusion: Patients with bilateral vertebral hypoplasia displayed a unique collateral supply, special stroke pattern, and younger stroke onset. Early recognition and stroke prevention should be considered critical in clinical practice.

Objectives Vertebrobasilar dolichoectasia (VBD) and vertebral artery hypoplasia (VAH) are known predisposing factors of posterior circulation stokes. These vascular conditions have unique hemodynamic patterns in neuroimaging studies; however, they have been presented as a single entity in some reports. The aim of this retrospective study was to clarify the relationship between these conditions with regard to ultrasound (US) findings. Methods A total of 465 patients with strokes were recruited. Brain magnetic resonance imaging of vertebrobasilar arteries and differences in extracranial side‐to‐side vertebral artery (VA) flow were recorded by US and compared in groups. Results The mean age of the 465 patients ± SD was 67.23 ± 12.13 years; 296 were men. The prevalence of VBD was 13.5% (n = 63), and 10.8% (n = 50) of the patients had coexisting VAH and VBD. These patients also had the highest prevalence of posterior circulation strokes (58% [n = 29]). A cutoff value of 55.65 mL/min and a ratio discrepancy of 5.28 (group median) for the side‐to‐side extracranial VA flow volume as detected by conventional US were also observed in the patients with both VAH and VBD. Conclusions Our study revealed a higher prevalence of posterior circulation strokes in the patients with both VBD and VAH. Chronic asymmetric hemodynamic shear force in extracranial VAs leading to deformity of the vertebrobasilar system may explain our observations. Accordingly, the blood flow volume and the ratio difference could potentially be used to detect patients at risk of VBD and reduce stroke risk factors.

No abstract