The Mechanism And Characteristics Of Vertebral Artery Hypoplasia Contributing To Posterior Circulation Infarction

Background Vertebral artery hypoplasia(VAH)is a common vascular variation in the genenal population,which refers that the diameter of vertebral artery is slender congenitally.It is reported that VAH may be a predisposing factor for posterior circulation ischemic events,especially when companied with other conventional vascular risk factors.However,to date,the exact pathomechanism of VAH contributing to posterior circulation infarction(PCI)and the characteristics of VAH and PCI is not clear.Objective To expore the possible pathomechanism of VAH contributing to PCI,we use brainstem auditory evoked potential(BAEP),blink reflect(BR),transcranial Doppler ultrasonography(TCD)and Nuclear Magnetic Resonance to test whether there are brainstem ischemia and the hemodynamics change of posterior circulation.At last,we further confirm whether VAH is an independent risk factor for PCI and investigate the characteristics of PCI that is related to VAH in suspected vertigo patients.Methods1.300 vertigo patients who were considered to be suspected PCI were enrolled consecutively from October 2014 to December 2015 in Zhengzhou people’s Hospital.They were divided into VAH group and non VAH group depending on the result of Magnetic Resonance Angiography(MRA)and contrast enhancement Angiography(CE-MRA),then PCI group and non PCI group according to whether acute infarction was found in diffuse weighted imaging(DWI).2.By means of BAEP and BR,we compare the change of the amplitudes,absolute latencies of waves I,II,III,IV,and V,interwave latencies of I–III,III–V,and I–V,as well as absolute latencies of waves of R1,R2 and R2’ between VAH group and non VAH group.3.TCD was used to measure and compare the changes of vertebrobasilar artery in systolic peak velocity,diastolic peak velocity,mean velocity,pulsatility index,resistance index,then we analyze the mean flow volume(MFV)and wall shear stresses(WSS)between VAH group and non VAH group.4.we explore further whether VAH is an independent risk factor for PCI and the characteristics of VAH related PCI.Results1.The abnormal rate of BAEP and BR and the percentage of PCI in the VAH group is significantly higher than the non VAH group(P<0.05);the absolute latencies of waves V,interwave latencies of III–V and I–V as well as absolute latencies of R1,R2 and R2’waves is longer in VAH group compared with the non VAH group(P<0.05).Upon the risk of PCI among vertigo patients companied with VAH,the area under the receiver operating characteristic curve(ROC)of the right V wave absolute latencies,the right III–V interwave latencies,the left and right I–V interwave latencies is 0.739,0.720,0.711 and 0.717 each other(P<0.05).When the right III–V interwave latencies ≥ 2.19 ms,the sensitivity and spectificity is 75% and 68.9%(P=0.011)on predicting the risk of PCI,when the absolute latencies of right R1 wave ≥ 11.35 ms,the sensitivity and spectificity is 56.3% and 64.4%(P=0.027)on vertigo patients with VAH.2.Compared with non VAH group,the Vs,Vd,Vm,MFV and WSS of the right vertebral artery and basilar artery decrease significantly(P<0.05),while there is no statistical difference between the two groups upon Vs、Vd、Vm、MFV、WSS、RI and PI of the left vertebral artery(P>0.05).3.Multivariate logistic regression analysis showed that VAH,stenosis of the posterior circulation and diabetes mellitus were independent risk factors for PCI.The TOAST subtype of PCI with VAH was mainly attributed to small artery occlusion(10/18).In addition,8 PCI patients with VAH that located above the confluence of bilateral vertebral artery,such as pontine and thalamus,mainly occurred on the contralateral side of VAH(8/11);4 PCI patients with VAH that situated below the convergence of vertebrobasilar artery,such as cerebellar and medullary infarction,mostly happened at the ipsilateral side of VAH(4/6).Conclusion1.On vertigo patients with VAH,there is subclinical ischemic on the brainstem and some value in predicting the occurrence of PCI when the right III–V interwave latencies of BAEP ≥ 2.19 ms and the right R1 wave absolute latencie of BR ≥ 11.35 ms.2.The blood flow,MFV,WSS of posterior circulation vessels are relatively slow,which may be related to the occurrence of PCI among VAH patients.3.On vertigo populations,VAH is a common vascular variation.At last,we come to the conclusion that VAH is an independent risk factor for PCI and there are some characteristics on PCI with VAH.