MELAS型线粒体脑肌病的MRI诊断

目的探讨合并乳酸血症和卒中样发作的线粒体脑肌病（MELAS）的磁共振成像（MRI）影像学特点。方法收集经临床病理证实的MELAS型线粒体脑肌病共6例，回顾性分析其MRI和磁共振波谱（MRS）资料。结果脑MRI检查，MELAS表现为大脑半球各叶大小不等片状病灶；病变位于脑皮质区，病灶的分布与脑血供分布不一致；自旋回波T1加权像呈低信号、T2加权像呈高信号；扩散加权成像（DWI）呈高信号。MRS分析显示病灶区见典型的乳酸盐峰，N-乙酰天门冬氨酸盐，肌酸值正常或略降低。扩散张量成像（DTI）显示病灶区脑皮质下白质纤维束破坏、中断、稀少。结论MELAS型线粒体脑肌病的病变形态、分布具有特征性，常规MRI与DWI、DTI及MRS等磁共振技术，对MELAS的定性诊断具有很高的价值。

Diagnosis of Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke by MRI

Objective To investigate the appearances of mitochondrial encephalomyopathy with lactic acidosis and stroke （MELAS） on MRI. Method MRI and magnetic resonance spectroscopy （MRS） data of 6 patients with MELAS confirmed by pathological examination were analyzed retrospectively. Results The multiple flaky lesions with varied size were observed in different lobe of brain on brain MRI of all the patients with MELAS. The lesions mainly located in the cerebral cortexes, and not distributed in accordance with cerebral vessels run. All the lesions showed low signal intensity on T1-weighted image, and high signal intensity on T2-weighted image and diffusion weighted image （DWI）. MRS showed a typical crest of lactate in MELAS lesions. The ratio of N-acetyl-aspartate to creatine was normal or decreased slightly on MRS. Diffusion tensor imaging （DTI） showed that the nerve fiber bundles of the white matter under the cerebral cortexes were broken off and degenerated. Conclusions The MELAS lesions appearance the on MRI and distribution of MELAS lesions in the brain were characteristic. Routine MRI and functional MR techniques such as DWI, DTI and MRS are of an important value to diagnosis of MELAS.