MELAS 综合征的 MRI 诊断

目的：回顾性分析线粒体脑肌病伴高乳酸血症和卒中样发作(MELAS)综合征的 MR 表现特点,提高对 MELAS 综合征早期诊断的能力。方法收集经临床诊断的 MELAS 综合征共16例,均由肌肉病理活检证实。所有患者均行 MR 平扫,其中3例行 ASL 扫描,15例行 MRA 检查,14例行 DWI 扫描,3例行 MRS 扫描,并回顾性综合分析其影像学资料。结果MRI 检查发现,本组 MELAS 综合征多表现为大脑半球各叶大小不等片状病灶,病变多位于大脑半球后部脑皮质区,向皮层下的白质蔓延,病灶的分布与脑血供分布不一致；自旋回波 T1 WI 呈低信号、T2 WI 呈高信号,FLAIR 呈高信号；DWI 呈高信号；3例行 MRS 分析提示病灶区典型乳酸峰；其中1例 MRA 检查提示病灶区分支血管增多,1例分支血管减少；3例行 ASL 检查提示病灶区高灌注。16例中4例随访病灶具有游走性、多变性、此起彼伏等表现,旧病灶有脑萎缩、脑软化等表现。16例行肌组织活检见破碎样红纤维(RRF)；电镜见线粒体体积增大、数量增多,肌纤维粗细不等,少数萎缩变细。3例行线粒体基因测序发现线粒体 DNA(mtDNA)A3243G 点突变。结论DWI、MRS 及 ASL 在 MELAS 综合征诊断中具有良好的价值。

The MRI findings of mitochondrial encephalomyopathy,lactic acidosis and stroke-like episodes

Objective To analyze retrospectively the MR features of MELAS patients,in order to improve the early diagnosis of MELAS.Methods MR data of 1 6 MELAS patients confirmed by clinical diagnose and muscle biopsy were retrospectively analyzed. MR features of plain scan(n=1 6),ASL(n=3),MRA(n=1 5),DWI(n=14)and MRS(n=3)were analyzed.Results MRI data demonstrated brain lesions mainly distributed in posterior cerebral hemisphere extending to subcortical area,which was not consistent with the vascular supply territories.The lesions were observed as low signal on Spin-echo sequence of T1 WI,while high signal on T2 WI, FLAIR and DWI.The focal lesions showed increasing Lac peak on MRS.Fifteen of 16 patients underwent MRA and one showed increased arterial branches in lesion zones.Three patients had ASL scanning demonstrating high irrigation in lesion zones which would wander once relapsed.Meanwhile,old lesions showed encephalatrophy and cerebromalacia.All patients’muscle biopsy pathology showed ragged red muscle fibers.Under electron-microscopic,bioblasts were bigger and more than average level and muscle fibers atrophied.Mitochondrial DNA sequence of 3 patients showed mtDNA A3243G transgenation.Conclusion The DWI,MRS and ASL sequences show good ability in MELAS diagnosis and differential diagnosis.