Acute necrotizing encephalopathy was initially reported in Japanese children. The rapid evolution and symmetrical brain lesions seen in the brainstem, cerebellum and specially in the thalamus characterize the disease. We studied a 7-month-old-girl, who presented with two episodes of rapid loss of consciousness and paresis without metabolic disturbances. At the first time she had a rapid improvement, but at the second episode the course was fulminant and in two days she lapsed into a clinical state of brain death. The magnetic resonance studies showed symmetrical lesions in the thalamus and additional lesions involving the brainstem and the cerebellum.