Objective To investigate the clinical and imaging characteristics of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome in adult, and to enhance the knowledge of this disease and decrease misdiagnose. Methods Relevant literatures were reviewed, and two cases of MELAS syndrome proved by muscle pathology were retrospectively analyzed. Results The two patients presented with the onset of stroke and seizures. Imaging examination: “cerebral infarction”-like lesions asymmetrically involving temporal parietal occipital lobe. CT scan showed patchy low density shadow. On MRI, lesions showed slightly long T1 and T2 signals, hyperintensity on FLAIR and DWI, slightly low signal on ADC map. The lesions involved the territories of middle cerebral artery and the posterior cerebral artery. Brain MRA scan showed supply artery stenosis or occlusion. The perfusion weighted imaging showed abnormal hyperperfusion in the lesion area. Magnetic resonance spectroscopy (TE=135 ms) scan showed obvious inverted lactate peak at lesions. Laboratory tests showed the lactate level of blood and cerebrospinal fluid increased significantly. For biceps brachii biopsy, the scattered and ragged red fibers can be seenon modified Gomori-trichrome. The two cases of last diagnosis is MELAS syndrome. For the mt DNA A3243G of detection, the first case was negative, but the second case was positive. The first patient returned one year later due to second onset, the new lesion involved temporal pole, brain atrophy was seen at the primary lesion area. Conclusion MELAS syndrome is rare in clinic, and clinical and imaging manifestations have certain characteristics. Multi-modality MRI has important value in the diagnosis of the disease. Final diagnosis relies on muscle histological examination.%目的：探讨成人MELAS综合征的临床表现和影像特点，提高对该病的认识，减少误诊。方法复习线粒体脑肌病相关文献，回顾性分析2例经肌肉病理活检证实的MELAS 综合征病人的临床和影像资料。结果病人均为卒中样起病伴癫间发作。影像检查提示：①不对称累及颞顶枕叶的“脑梗死”样病灶：CT 示片状低密度影，MRI 示片状稍长T1稍长T2信号，FLAIR 呈高信号，扩散加权成像（DWI）呈高信号，表观扩散系数（ADC）图呈稍低信号；②病变同时累及大脑中动脉及大脑后动脉供血区；③MR血管成像（MRA）未见相应供血动脉狭窄或闭塞；④灌注加权成像（PWI）显示病变区异常高灌注；⑤磁共振波谱成像（MRS，TE=135 ms）示病灶区明显倒置的乳酸峰。实验室检查示血和脑脊液中乳酸含量明显升高。肌肉活检（改良Gomori Trichrome 染色，MGT）示细胞内散在破碎红纤维。2例均确诊为MELAS综合征。基因检测线粒体DNA（mt DNA） A3243G点突变情况，病例1呈阴性，病例2呈阳性。病例1的病人于首次发病1年后复发，新发病灶向颞极迁移，原发病灶累及脑区萎缩。结论MELAS综合征临床较为罕见，临床表现和影像改变具有一定的特征，多模态MRI检查对本病的临床诊断具有重要的价值。最终确诊依赖于肌肉病理组织学检查。
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