扩散成像和磁共振波谱对MELAS诊断价值的初步研究

摘要

目的:探讨扩散成像(DWI、DTI)和磁共振波谱(1H-MRS)对MELAS患者的诊断价值.材料和方法:采用3.0 T磁共振,对5例经病理证实的MELAS患者进行常规磁共振及DWI、DTI和1H-MRS检查.结果:5例MELAS患者常规磁共振可见大脑皮层多发脑回状长T1长T2及高FLAIR异常信号,增强扫描无强化,病灶具有游走和复发特点.DWI病变区呈稍高信号,ADC图呈稍高或稍低或混杂信号;DTI显示白质纤维信号减低;1H-MRS可见NAA峰降低,高大Lac峰出现.病灶区与对侧正常区比较ADC值增高(P<0.05),FA值降低(P<0.01),NAA/Cr降低(P<0.05),Lac/Cr明显增高(P<0.01).结论:常规磁共振发现大脑皮层反复出现的多发游走性无强化病灶,要考虑到MELAS型线粒体脑肌病的可能性,DWI结合ADC图有助于明确MELAS的病理损害性质,DTI可直观显示白质纤维破坏程度,1H-MRS检测到异常高大Lac峰是支持MELAS的重要辅助依据.%Purpose To investigate the value of DWI, DTI and 1H-MRS on diagnosis of mitochondrial encephalopathy with lactic acidosis and strokelike spells (MELAS).Materials and Methods The image data of 5 patients with MELAS proved by pathology were obtained by rountine MR scan, DWI, DTI and 1H-MRS,and the change of ADC、FA、NAA/Cr、 Cho/Cr and Lac/Cr were quantitatively determined on 3.0T MR.Results The lesions of 5 patients with MELAS showed hypointense on T1WI, hyperintense on T2WI and FLAIR.The abnomal signals located at cerebral cortex, especially parietal lobe, temporal lobe and occipital lobe, which had the feature of transmigration, recurrence and non-enhancement.The lesions showed slightly hyperintense on DWI, slightly hyperintense or hypointense or mix-intense on ADC images, decreasing signal intensity of fiber in white-matter and FA on DTI.The lesions also displayed decreasing NAA peak, non-increasing Cho peak and obviously increasing Lac peak on 1H-MRS.The quantitative analysis manifested that ADC increased(P＜0.05) ,FA decreased(P＜0.01), NAA/Ct decreased(P＜0.05) ,and Lac/Cr obviously increased(P＜0.01)in the focal lesions than the normal controls.Conclusions DWI has high sensitivity for diagnosis of MELAS.ADC images can distinguish acute between chronic stage of MELAS.DTI can clearly show the degree of destroy of fiber in white-matter.The prominent increasing Lac peak on 1H-MRS is a significant evidence to support MELAS.