ABSTRACT
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.