We report a 36-year-old man with MELAS in whom a 5-month course of hig
h-dose oral idebenone, a derivative of coenzyme Q(10), increased marke
dly cerebral metabolic ratio of oxygen and oxygen extraction fraction
without increased cerebral blood flow with PET. The results indicate t
hat idebenone improves mitochondrial oxidative metabolism in the brain
and suggest a therapeutic potential of idebenone for MELAS.