MR Imaging and Proton Spectroscopic Study of Stroke-like Episodes in MELAS / 实用放射学杂志

ABSTRACT

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.