MEL AS综合征的MRI和MRS表现及临床意义

目的：分析线粒体脑肌病并高乳酸血症与卒中样发作（MELAs）综合征的MRI和MRS表现，探讨MRI对该病早期诊断与鉴别诊断的临床价值。方法：回顾性分析24例经临床表现及肌肉病理活检确诊的MELAS综合征患者，24例均行常规MRI（包括T1WI平扫与增强扫描，T2WI，T2FLAIR），14例行MRA，3例行DwI，3例行MRS。综合分析所有病例的多模态MRI特征。结果：24例（79个病灶）均出现大脑皮质或皮质下片状长T1长T2信号，以枕叶（29个）、颞叶（25个）和项叶（16个）受累为主，可双侧出现；14例MRA示病变区与动脉供血区域不吻合，4例可见血管增生；10例随访患者中7例发现病灶具有游走性；3例行DWI患者均可见扩散受限所致异常信号；TzFLAIR可同时显示新、旧病灶（呈不同程度高信号），且所显示慢性期病灶的数目与DwI相同（2例）或更多（1例）。3例MRs均可见乳酸（Lac）峰增高，且不局限于MRI所显示的病灶内，1例较陈旧病灶可见氮一乙酰天门冬氨酸（NAA）峰降低。结论：MELAS综合征具有较特异的MRI表现；MRS提示病灶内和病灶外Lac峰增高，结合高乳酸血症，对该病早期确诊有重要价值。

MR imaging and MR spectroscopy features of MELAS and their clinical values

Objective： To analyze the features of magnetic resonance imaging （MRI） and magnetic resonance spectros- copy （MRS） in patients with mitoehondrial encephalomyopathy with lactic acidosis and stroke-like episodes （MELAS）, and to explore the clinical value of MR for early diagnosis and differential diagnosis of MELAS. Methods.. 24 cases of MELAS patients confirmed by clinical features and pathology via muscle biopsy were retrospectively reviewed. All of them under- went MRI （including T1WI with and without Gd-DTPA enhancement, T2WI, T2-FLAIR）, and 3 of them also underwent MRS, 14 cases also MRA,3 cases also DWI. A comprehensive analysis was performed on the multi-modal MRI data to sum- marize the common features, and to explore the correlation between imaging and pathology, the MR diagnostic value and the clinical pathway for differential diagnosis. Results In all 79 lesions were found cortical or subcortieal patchy areas of hyperin- tense signal on Tz WI and hypointense signal on T1WI, the majority of them located in the occipital lobe （n=29）, the tempo- ral lobe （n= 25）,or the parietal lobe （n= 16）, either unilaterally or bilaterally. The lesion did not coincide with the cerebral artery territory in 14 cases,and demonstrated hypervascularity （4 cases） on MRA. Follow up in 10 cases revealed a migra- ting pattern of the lesions （7 cases）. DWI was more sensitive to new-onset lesions whose diffusion was restricted （3 cases） while T2-FLAIR could display both ehronic and new-onset lesions which demonstrated different degrees of hyperinstenstiy, and the number of chronic lesions displayed on Tz-FLAIR was equal to （2 cases） or more than that of diffusion-restricted lesions on DWI （1 ease）. MRS revealed increased lactate peak （Lae） （3 eases） which was not limited within MRI-visible le- sions,and nitrogen-acetyl aspartic acid （NAA） peaks （1 case） deereased in some old lesions. Conclusion： MELAS demon- strates characteristic imaging features. MRS-visible lactate peak within and outside lesions, together with lactic acidosis, helps to confirm the diagnosis.