兔蛛网膜下腔出血急性期MSCT灌注及MR DWI初步研究

目的:探讨兔蛛网膜下腔出血(SAH)急性期脑组织微循环和水分子扩散等的改变及其两者间关系。方法:将58只新西兰大白兔随机分为3组:A组,正常组,10例;B组,SAH组,24例;C组,假手术组,24例。以枕大池二次注血法制作兔SAH模型,分别于术后5～90min行MSCT灌注及MR DWI扫描,观察兔脑血流量(CBF)、脑血容量(CBV)、平均通过时间(MTT)及表观扩散系数(ADC)的变化。结果:首次枕大池注血后5min,兔脑皮层CBF、CBV即显著升高,15min CBF、CBV升高达峰值,30、60和90minCBF、CBV逐渐降低,但90min仍高于正常组和假手术组。二次注血后,兔脑皮层CBF、CBV上升较首次注血后缓慢,幅度亦有所降低,于二次注血后30min上升达峰值。兔SAH急性期脑CBF、CBV变化为全脑弥漫性改变,基底节区变化趋势与大脑皮层一致。SAH组动物首次注血后10～90min连续观察,ADC异常脑区范围逐渐扩大,双侧基底节区ADC值均明显低于正常组和假手术组,90min回升,与对照组间差异无显著性意义。二次注血后ADC值下降更为明显,于注血后20min降至最低点,然后逐渐回升,90min尚未回复基线水平。结论:SAH急性期脑损伤并非直接由脑血流量下降引起,皮层传播抑制(CSD)可能参与SAH后急性期的发病级联。

Preliminary Study of Subarachnoid Hemorrhage in Rabbits with MSCT Perfusion and MR Diffusion Weighted Imaging

Objective:To explore the alterations of cerebral microcirculation and diffusion in rabbit subarachnoid hemorrhage(SAH)and their relationship.Methods:Fifty-eight adult New-Zealand rabbits were randomly assigned into 3 groups:group A(normal control,n=10),group B(SAH,n=24),group C(sham-operated control,n=24).Rabbit SAH model was produced by a two-hemorrhage method(blood injection into the cisterna magna).CT perfusion and MR diffusion weighted imaging were performed within 90min after operation.The CBF,CBV,MTT and ADC maps were then obtained and the related values were calculated.Results:CBF,CBV of cerebral cortex were elevated obviously five minutes after the first blood injection and reached peak at 15min,which were reduced gradually at 30,60,90min after the first blood injection,but were still higher than those in control groups at 90min.The two parameters were elevated more slowly after the second blood injection than after the first injection,and the amplitude was decreased.Both reached peak at 30min after the second blood injection.The changes of CBF,CBV were diffuse throughout the brain,and the change in basal ganglia was similar to that in cerebral cortex.Observing continuously from 10 to 90 minutes after the first blood injection,we found that the abnormal region of ADC was enlarged gradually,and the ADC values of bilateral basal ganglia were obviously lower than those of the normal and sham operated group,which recovered at 90min and had no signifcant difference from control.The ADC value was decreased obviously after the second blood injection and was decreased to the lowest point at 20min after operation,then it began to recover gradually,but it was still lower than that in control at 90min.There were no correlations between changes of CBF,CBV and ADC values.Conclusion:A reduction in blood flow may not be the direct cause of the brain injury at acute stage after SAH.Cortical spreading depression(CSD)might participate in the cascades at acute stage after SAH.