Background:Studies on the relationship between antiepileptic drug (AED) administration and clinical outcomes in patients with mitochondrial encephalomyopathy,lactic acidosis,and stroke-like episodes (MELAS) remain scarce.Levetiracetam (LEV) is an AED that is neuroprotective in various neurologic disorders.This study aimed to determine the impact of LEV on the outcome of MELAS.Methods:A retrospective,single-center study was performed based on a large cohort of patients with MELAS with a history of seizures (n =102).Decisions on antiepileptic therapies were made empirically.Patients were followed up for 1 to 8 years (median,4 years) and divided into 2 groups based on whether LEV was administered (LEV or non-LEV).The modified Rankin scale (mRS)scores and mortality risks were analyzed in all patients.Results:LEV,carbamazepine,benzodiazepines,topiramate,oxcarbazepine,valproate,and lamotrigine were administered in 48,37,18,13,11,9,and 9 patients,singly or in combination,respectively.The mean mRS score of the LEV group (n =48) was lower than that of the non-LEV group (n =54;mean ± standard deviation,2.79 ± 1.47 vs.3.83 ± 1.93,P =0.006) up to the end of the study.Nevertheless,there was no difference in the proportion of subjects without disability (mRS ranging 0-1) between the groups (P =0.37).The multivariate regressions revealed that LEV treatment was associated with lower mRS scores (odds ratio 0.32,95％confidence interval [CI] 0.15-0.68,P =0.003) and mortality rates (hazard ratio 0.24,95 ％ CI 0.08-0.74,P =0.013).There was a significant difference in the Kaplan-Meier survival curves between the groups (x2=4.29,P =0.04).Conclusions:The LEV administration is associated with lower mortality in patients with MELAS in this retrospective study.Further laboratory research and prospective cohort studies are needed to confirm whether LEV has neuroprotective effects on patients with mitochondrial diseases.