急性实验性变态反应性脑脊髓炎模型的MRI表现及其病理基础

目的 探讨急性实验性变态反应性脑脊髓炎(EAE)模型的MRI表现及其病理基础.方法 用豚鼠全脑脊髓匀浆诱导EAE大鼠模型(6只),观察其体重变化和临床表现,同时设对照组(6只).在EAE大鼠发病后进行MR常规扫描、钆剂增强扫描,并静脉使用超小超顺磁性氧化铁(USPIO),24 h后行USPIO增强扫描,扫描完毕立即处死大鼠取脑,行脑组织切片的HE染色、髓鞘染色和普鲁士蓝染色.观察MRI和病理检查的异常所见,并进行对照.结果EAE大鼠组在诱导后第8～9天开始体重下降,在第10～11天出现临床症状.MR常规扫描未见明确异常,钆剂增强后仅见脑膜弥漫增厚及增强,USPIO增强扫描可见T2WI上延髓实质内大片低信号区,T1WI可见对应部位的高信号.梯度回波T2*WI比T2WI显示在脑干病灶以外的小脑白质内低信号.临床评分高的大鼠其低信号范围也较大.对照组大鼠未见异常.病理检查发现发病大鼠脑白质内散在血管套袖,部分伴相邻区域的脱髓鞘改变.普鲁士蓝染色发现病灶内巨噬细胞胞质内有蓝染颗粒,沉积部位与T2WI上低信号对应.结论USPIO增强MRI可以揭示常规MRI和钆剂增强成像未能显示的急性EAE病变,活体显示EAE病灶内巨噬细胞的分布,具有重要的研究价值和应用前景.

MRI of acute experimental allergic encephalomyelitis: correlation with pathology

Objective To investigate the MR imaging findings of acute experimental allergic encephalomyelitis(EAE) in correlation with pathology. Methods An EAE model was induced by intradermal inoculation with guinea pig CNS homogenate in 6 female Lewis rats.Another 6 rats served as control.The clinical presentation and body weight of the animals were recorded daily. Routine MRI,Gd-enhanced MRI were performed when EAE animals showed the initial symptoms. Uhrasmall superparamagnetic iron oxide(USPIO) colloid solution was also administrated intravenously and MRI was performed again after 24 hours. The brain was removed instantly after the second MR imaging. The pathological exams including HE staining,myelin sheath staining and prussian staining were performed.The imaging findings were observed in correlation with pathological results. Results The EAE rats showed decrease of body weight on the 6th to 7th day after inoculation,and the clinical symptoms appeared on the 10th to 11th day after inoculation.Routine MRI did not show any definite abnormalities.The Gd-enhanced MRI found the diffuse thickening and enhancement of brain meninges.The USPIO-enhanced MRI showedareas of low signal intensity at white matter of medulla oblongata on T2WI,and high signal intensity was observed at the corresponding area on T1 WI. Gradient T2 * WI found more foci of low signal intensity in eerebellar white matter besides the lesions in the brain stem.The range of abnormal signal intensity was larger in animal with higher clinical scores than that with lower score.There were no abnormal findings in control animaL The pathological exam found "perivascular cuff" in the brain white matter in EAE animals,some accompanied with adjacent demyelinatian. The prussian staining found blue particles within the cytoplasm of the macrophages around the lesion,which corresponded to the area of low signal intensity on T2WI.Conclusion USPIO-enhanced MRI could reveal acute EAE lesions which were not capable of being shown on routine MRI and Gd-enhanced MRI.It can image the macrophages around the lesions in vivo.USPIO is important for future research and application in MS patients.