Creutzfeldt-Jakob disease has a higher incidence in Chile than in other countries. The post mortem pathological characterization of brain tissue is necessary to reach a definitive diagnosis. We report a 73 years old man with a history compatible with of a rapidly progressive dementia, in which the first electroencephalographic study showed a pattern consistent with non-convulsive status epilepticus. Besides discarding this diagnosis, it was necessary to rule out other causes of rapidly progressive dementia such as Hashimoto encephalopathy. Finally, the sustained clinical deterioration with no response to anticonvulsants and corticosteroids, the imaging studies, a serial electroencephalographic monitoring study and the detection of 14-3-3 protein in cerebrospinal fluid were the keys to achieve the diagnosis of the disease.

A3243G mutation is associated with several mitochondrial disorders, MELAS syndrome being the most common. Polymicrogyrias constitute an extensive group of malformations of cortical development due to abnormal cortical organization. The association between MELAS/A3243G mutation and polymicrogyria is extremely rare; in 18 years of investigation regarding A3243G mutation and related disorders only one case has been reported. We describe a female patient with proven MELAS/A3243G mutation, developmental delay and mild left hemiparesis in whom MRI showed extensive bilateral polymicrogyria. The association of these two disorders and their possible relation are discussed.

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