Subacute spongiform encephalopathies are rare fatal diseases that affect the central nervous system, which is thought to be caused by prions, characterized clinically by a rapid progressive dementing course, along with generalized myoclonus. The prototype of these conditions in humans is Creutzfeldt-Jakob Disease (CJD). Although the final diagnosis depends on neuropathological examination, the presence of periodic sharp wave complexes on EEG and of the neuron-specific enolase, tau protein, S-100, and of the 14-3-3 protein in the cerebrospinal fluid, make the diagnosis of probable CJD. However, as these criteria are not completely accurate and the early diagnosis is extremely difficult, much interest has been focused recently on imaging methods. With the advent of diffusion-weighted imaging, MRI has shown high sensitivity and specificity, therefore being considered a useful method for the early diagnosis of this entity.