线粒体脑肌病卒中样病灶的磁共振诊断及波谱分析

目的 探讨线粒体脑肌病伴高乳酸血症与卒中样发作事件(MELAS)脑内卒中样病灶的磁共振成像表现及~1H磁共振波谱特征.方法 回顾分析7例MELAS患者的临床及磁共振检查资料.结果 本组病例所行12次磁共振检查共计评价超急性期卒中样病变12个、急性期病灶12个、亚急性10个和慢性病灶6个.MELAS脑内卒中样病灶最初表现为局限大脑皮层的水肿信号灶,可累及皮层下区,多发于颞、枕、顶叶.磁共振扩散加权成像,病变在超急性期(3 d内)表现为以细胞毒性水肿为主,呈边界清楚的高信号灶;急性期(4～7 d)、亚急性期(2～4周)至慢性期(＞4周)病变逐步扩大,边界变模糊,以血管源性水肿为主.~1H磁共振波谱分析,脑卒中样病变在早期以高耸的双乳酸峰为特点,伴N-乙酰天门冬氨酸(NAA)等脑代谢物成分不同程度降低;随后,乳酸峰逐步降低,NAA等代谢物浓度可部分恢复.结论 MELAS卒中样病灶主要累及大脑皮层和皮层下区,细胞毒性水肿出现早但持续时间短,~1H磁共振波谱以典型的双乳酸峰为特征并伴有NAA浓度降低.

MR Imaging and Proton Spectroscopic Study of Stroke-like Episodes in MELAS

Objective To study the characteristics of MR imaging and proton MR spectrscopy(~1H MRS)of stroke-like lesions in MELAS.Methods Clinical,MR imaging and proton spectroscopic findings of stroke-like lesions in 7 patients with confirmed MELAS were analyzed retrospectively.Results A total of 12 MR investigations had been performed in 7 patients.Stroke-like lesions showed by MR imaging included superacute in 12,acute in 12,subacute in 10 and chronic stage in 6.Early stroke-like lesions were demonstrated as focal edematous foci mainly involved cortex/subcotical areas of occipital,temporal and parietal lobes.At MR diffusion imaging,stroke-like lesions in the superacute(＜3 days)stage were showed as well-circumscribed lesions with high signal intensities for cytotoxic edema.During the acute(4～7 days),sub-acute(2～4 weeks)and chronic(＞4 weeks)stages,the lesions gradually expanded,and became blur,and presented with vasogenic edema mainly.Proton spectroscopy showed a prominently elevated lactate,varied decrease of NAA concentration and other brain motabolites in the stroke-like lesions early after onset,and depicted gradual decrease of lactate level and partial recovery of NAA concentration subsequently.Conclusion Stroke-like lesions in MELAS mainly involve the cerebral cortex and subcortical areas,in which cytotoxic edema appears early but for a short period.In ~1H MRS,the lesions are characterized by a double lactate peak with decrease of NAA concentration.