低氧致脑水肿的磁共振扩散加权成像和病理观察

目的 通过对模拟高原低氧致脑水肿的磁共振扩散加权成像和病理改变的研究,探讨高原脑水肿的病理基础.方法 选320～380 g的雄性Wistar大鼠32只,按体重随机分为常氧组、4 000 m组、6 000 m组和8 000 m组各8只.后3组动物置于低压舱中模拟海拔4 000 m、6 000 m、8 000 m高原低氧环境持续8 h后,对所有大鼠进行扩散加权成像检查及脑组织的光镜和电镜观察.结果 低氧处理的各组扩散加权成像均出现低强度信号,表观扩散常数值升高.与常氧组比较,4 000 m组表观扩散常数值的升高无明显差异,6 000 m组和8 000 m组表观扩散常数值升高有显著性差异.病理检查显示,4 000 m组脑组织呈现混合性脑水肿,血脑屏障轻度损伤;6 000 m组以血管源性脑水肿为主,血脑屏障损伤加重;8 000 m组重度血管源性脑水肿,血脑屏障破坏解体.结论 低氧所致的脑水肿主要是血管源性脑水肿,其病理基础是低氧导致的血脑屏障损害.

Observation of Diffusion Weighted MRI and Pathology of Cerebral Edema during Hypoxia

Objective To explore the pathological basis of high altitude cerebral edema(HACE) by studying changes in diffusion-weighted imaging(DWI)and pathology of cerebral edema during hypoxia. Method Thirty-two Wistar rats (weighted 320~380 g) were randomly divided into normoxic group, 4 000 m group, 6 000 m group and 8 000 m group (n=8 for each group). Rats in the latter three groups were placed in hypobaric chamber to simulate the hypoxic environment at 4 000 m, 6 000 m, 8 000 m altitude above sea level for 8 h, respectively. Brains of all the rats were observed by DWI and examined with light and electronic microscopes. Result In the three hypoxic groups, signals of the lower intensity were found in DWI, and apparent diffusion coefficient (ADC) value was increased. There was no significant difference between ADC values of normoxic group and 4 000 m group, while ADC value was increased significantly in 6 000 m group and 8 000 group. Pathologic change of cytotoxic and vasogenic brain edema and damage in blood-brain barrier (BBB) were found in 4 000 m group and the vasogenic brain edema and the damage in BBB were much more serious in 6 000 m group. Severe vasogenic brain edema was found and the BBB disintegrated thoroughly in 8 000 m group. Conclusion Brain edema during hypoxia is mainly vasogenic brain edema (VBE) and the pathological basis is BBB damaged.