MELAS综合征的随访MRI分析

目的：随访分析线粒体脑肌病合并高乳酸血症与卒中样发作（MELAS）综合征的动态MRI影像学特征。方法：回顾性分析2005年9月至2015年4月确诊的MELAS综合征患者15例，男9例，女6例，平均15.5岁。所有病例在急性发作期（30 d内）均行常规MRI检查（包括T1WI平扫、T2WI、FLAIR及DWI），14例在急性发作期后（30～60 d）复查MRI，其中8例随访时行磁共振波谱（MRS）检查；10例在缓解期（＞60 d）复查常规MRI。着重分析病变的部位、信号、范围及其动态变化。结果：在急性发作期，单侧大脑皮层或皮层下受累占46.7%（7/15），双侧大脑皮层或皮层下同时受累占53.3%（8/15），双侧基底节受累4例，脑干受累1例。病灶在T1WI上呈低信号，在T2WI上呈高信号，在DWI上呈等或高信号。在急性发作期后，14例中，64.3%（9/14）病例的部分病灶范围扩大；71.4%（10/14）病例的部分病灶缩小，42.9%（6/14）的病例出现新的病灶。8例MRS检查中均出现Lac峰增高，2例病灶对侧脑组织出现Lac双峰，6例出现NAA峰降低。在缓解期，40%（4/10）的病灶出现脑萎缩，40%（4/10）的病灶出现软化灶。结论：MELAS综合征的病灶多为大脑皮层或皮层下游走性病灶，MRS会出现增高的Lac峰，随着病程发展会出现脑萎缩和病灶减小，结合临床资料，可早期提高其诊断的准确性。

The follow-up analysis of MR imaging in MELAS syndrome

Objective: To analyze the MRI features of dynamic change of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS). Methods: The clinical data and imaging findings of 15 cases of MELAS patients were retrospectively analyzed. All of patients underwent MRI examinations (including T1WI, T2WI, T2FLAIR and DWI) in acute attack stage (within 30 days). Forteen cases underwent MRI scanning after the acute attack stage (between 30 days～60 days), of which 8 cases were examined on MRS. Ten cases were repeated the MRI examinations in remission stage (>60 days). The location, range, signal intensity and dynamic change of the lesions were intensively analyzed. Results: In acute attack stage (within 30 days), 46.7% (7/15) unilateral cortical or subcortical cortex were affected, 53.3% (8/15) on bilateral cortical or subcortical cortex, 4 cases on bilateral basal ganglia and 1 case on brainstem. The gray matter of all 15 cases was hypointense on T1WI, hyperintense on T2WI and isointense or hyperintense on DWI. After the acute attack stage (between 30 days and 60 days) of the 14 cases, the lesions expanded in 64.3% cases (9/14), shrinked in 71.4% cases (10/14), and new foci emerged in 42.9% cases (6/14). Lactate peak increased in the fresh lesions of 8 cases, and the Lac peak increased in the contralateral area in 2 cases, while the nitrogen-acetyl aspartic acid (NAA) peaks decreased in 6 cases. In remission stage (>60 days), the atrophy was found in 40% cases (4/10) and encephalomalacia foci were found in 40% cases. Conclusion: Transient lesions are easily referred to the cerebral cortex and subcortex in MELAS patients. MRS shows prominent increasing peak. Brain atrophy in the MELAS patients develops gradually and stroke-1ike lesions shrink with progression of the disease. Combined with clinical data, the accuracy of early diagnosis of MELAS syndrome can be improved.