Objective:To compare the clinical and imaging characteristics between central nervous system vasculitis(CNSV)and mitochondrial encephalomyopathy (ME),so as to analyze the differential diagnosis of the two disorders.Methods: Clinical data on seven patients with CNSV and five with ME were retrospectively analyzed.The clinical manifestations,laboratory parameters,imaging features and histological characteristics were compared to screen for the evidence of their differential diagnosis.Results: The MRI results of both CNSV patients and ME patients (MELAS type) showed a multi-lesion pattern.The symptoms of CNSV patients included headache,limbs weakness,and erythrocyte sedimentation rate (ESR) increase.The symptoms of MELAS patients included epilepsy and increased serum lactic acid.The electroencephalographic manifestations of both diseases were abnormal:CNSV patients mainly had diffused lesions accompanied with limited alterations; ME patients had evidence of epileptic discharge,which was consistent with the clinical symptoms.Conclusion: Clinical manifestations of CNSV and ME patients are more valuable than imaging findings in the diagnosis of the two diseases.CNSV is characterized by vascular disorders and inflammatory reactions; ME is characterized by abnormal energy metabolism and severe damage of gray matter.The final diagnosis should depend on laboratory and histological examinations.