In a 13-month-old boy with recurrent motor deterioration provoked by fever MRI and proton MRS detected a leukoencephalopathy with reduced cerebral metabolites and elevated lactate. At follow-up 6 and 16 months later these abnormalities improved gradually. Serial diffusion tensor imaging revealed a stroke-like pattern with an initial strong reduction of the apparent diffusion coefficient followed by elevated values 6 months later. The relative diffusion anisotropy remained reduced. Muscle biopsy confirmed a mitochondrial encephalomyopathy.